Archaeological Basketry Treatments

May 13, 2010

 Table by Dana K. Senge and Ellen Carrlee, updated May 2010

Most recent version to be seen at Dana’s website: http://waterloggedbasketry.blogspot.com

Reviewed by Kathryn Bernick, May 2010

table for pdf

Site Treatment Condition Notes
Site: Alouette Basket Site (DhRp 19)Date recovered/treatment:Location of Collections: RBCM[1]  Materials: warp: red cedar branch or trunk, weft: spruce root, IDs by ML Florian (Bernick:1991)

Age:  

Burial Conditions: “a film of blue-grey clay covers the elements indicating that it was once buried in the type of matrix characteristic of wet sites” (Bernick 1991, pg 110)

Deterioration:

SOLVENT DRY“…immersion for one week in 10% ethanol, then increasing proportion of ethanol by 10% every week for 10 weeks (until reaching 100%)…  slowly dried between sheets of plate glass…”  (RBCM Conservation Lab records: 2629) 1991: “Wood elements rigid and apparently stable”.  (Bernick 1991, pg 111)2010: To date the authors have not examined the basketry material from this site.
Site: Axeti (FaSu 1)  Date recovered/treatment: 1969-72Location of Collections:  Museum of Archaeology and Ethnology, Simon Fraser UniversityMaterials: inner bark from western red cedar, root and splints.

Age: 1500 –1710 years +/- 80 

Burial conditions:

Deterioration:

PEG TREATMENT % MW: 10% solution of PEG close to 4000 Duration: immersion varied from several weeks to three months depending on density of artifact.Heated? No 

Drying: Air-Dried

(Hobler 1976)

2010:
Site: Beach Grove (DgRs 1)Date recovered/treatment: 1962Locations of Collections: LoA of UBC[2]Materials: No reference found identifying material types or species thin wood splints, likely red cedar (Bernick 2010) 

Age: Age of water-saturated component: 1603 years old +/- 120

Burial Conditions: stratum of finely textured silty clay of bluish-grey color below watertable (Fraser delta alluvial deposits, anaerobic)

Deterioration:

One fragment of basketry treated in field by the archaeologists and block-lifted on slab of mud; no further treatment of the basketry (Bernick, 2010).Others were treated with applications of Houston No. 3 Preservative supplied by the B.C. Provincial Museum (now RBCM) and “Firewater”“…excavators preferred the Firewater because it hardened the punky wood…” (Bernick 1991, pg 113) 1991: “…artifacts are shrunken and brittle, and, in most cases, the wood has severely checked…basketry was block-lifted-… still firmly set on a slab of mud” (Bernick 1991 pg 113).2010: To date the authors have not examined the basketry material from this site. Upon the recommendation of collection manager at LoA of UBC requests were made in 2008 and 2009 to the Tsawwassen and Musquem Bands for permission to examine and possibly sample material from the collection were unanswered.
Site: Biderbost  (45 SN 100)Date recovered/treatment: 1959-early 1970s/likely treated immediately upon recoveryLocation of Collections: Burke Museum[3] Materials: wood splints, presumed to be western red cedar withes or roots 

Age: ca. 2000 BP

Deterioration:

COAT WITH ADHESIVEPainted or soaked in a solution specially prepared (25% Plyamul Adhesive #9153- polyvinyl acetate soln from Reichold Chemical (now Forbo) and 75% Firewater (50cc heavy detergent of Firewater Company of Los Altos)  (Nordquist:1976) 2009: Material is dark brown, dry in appearance.   Some spots of surface sheen from adhesive.  Dirt glue to surface of inner bark elements.Elements are rigid but have some flexibility, not brittle with minor pressure.
Site: Blundell Road Basket (DgRs 15)Date recovered/treatment: 1967Location of Collections: LoA at UBC Materials: wood splints, likely western red cedar withe

Age: 2180 +/- 170 BP (direct date on the basket)

Burial conditions: find site: 4 feet deep in sphagnum peat, probably a slough when originally deposited (Bernick:1991)

Deterioration:

AIR DRYBasketry was not treated with any preservative. (Bernick 1991, 114) 1991: “wood is now brittle and somewhat shrunken.  Matted sphagnum moss… still adheres to large portions of the surfaces”. (Bernick 1991, pg 114).2010: To date the authors have not examined the basketry material from this site.
Site: Castle Hill (49-SIT-002)Date recovered/treatment: 1995-1998Location of Collections: Alaska State MuseumMaterials: likely spruce root

Age of Collections: ~ 700 radiocarbon years

Burial conditions:

Deterioration: Little deterioration

 

AIR DRYNot fully waterlogged when found, only slightly damp. Basketry slowly air-dried in fridge for several years, exact time it took to dry unknown.(Alaska State Museum treatment records) 2009: Stable. Can be safely handled and turned over for examination.
Site: Conway wet site (45 SK 59b)Date recovered/treatment: 1970Location of Collections: BurkeMaterials: some entirely cedar bark, some eintrely wood splints (likely cedar withes), some a combination (Bernick 2010)

Age of Collections: ~ 700 radiocarbon years

Burial conditions:  anaerobic alluvial deposits below watertable in Skagit River delta; a slough when originally deposited;  

Deterioration:

PEG TREATMENTMaterials were soaked in ethanol (95%) for two days, then:% MW: 33% PEG 1000 Duration: 2-4 days 

Heated? No

Drying: Air-dried on racks for 1-2 weeks

(Munsell 1976)

1976: recommend subsequent retreatment since basketry appears dry. (Munsell 1976)2009: Color variations from red-brown, black and light grey.  Light grey from remaining soil matrix. Some have a great deal of variation in tone, others all black.  Basketry materials dry in appearance (not waxy, saturated etc).Materials are stiff with some flexibility on in the elements. 
Site: Cowichan Bay Site Date recovered/treatment: ~2000Location of Collections: possibly RBCMMaterials:

Age:  

Burial conditions:

Deterioration:

AIR DRYAir dried following excavation.  Sent to CCI to see if condition could be improved.  Currently at CCI. (Confirm?) 2010:
Site: DgRs 36Date recovered/treatment: 1990’s Location of Collections: possibly at UBC?Materials:

Age: ca. 2100 years old

Burial conditions:  found in back dirt pile possibly came from same location as Water hazard (DgRs 30) 

Deterioration:

Possibly treated at RBCM% MW: Duration: Heated?

Drying:

2010:
Site: DhRq 19Date recovered/treatment: 1990-93 Location of Collections: Materials: western red cedar inner bark and limb/root

Age: radiocarbon dates average ca. 900 BP

Burial conditions:  found eroding out of the Fraser River beach in a tidal environment. 

Deterioration: The materials looked to be in good condition when found (Bernick 2010)

Possibly treated at RBCM% MW: Duration: Heated?

Drying:

2010:
Site: DgRn 9Date recovered/treatment: 1960’s Location of Collections: RBCMMaterials: western red cedar splints

Age: style indicates it is 2000 years old

Burial conditions:  found eroding from Fraser River Beach in Fraser Valley  

Deterioration:

Possibly treated at RBCM ?No treatment records?Each fragment appears to have been treated using a different method? (Bernick 2010) 2010:
Site: Ditidaht Sites DeSf 9 and DeSf 10Date recovered/treatment: 1994 Location of Collections: RBCM (requires permission of Parks Canada, Ditidaht First Nation and RBCM)Materials: western red cedar inner bark

Age: ca. 600 BP

Burial conditions: Deterioration:

(Bernick 2010)

Treated at Parks Canada in Ottawa (contact for treatment information)% MW: Duration: Heated?

Drying:

2010:
Site: English Camp Site (45 SJ 24)Date recovered/treatment: 1971 Location of Collections: Burke MuseumMaterials: 2 basketry artifacts: one is a basket fragment of wood splints, likely western red cedar withes;  the other is a hat possibly of western red cedar inner bark (Bernick 2010).

Age: ca. 2000 years old

(Sprague 1976)

Burial conditions:  anaerobic water-saturated deposits at bottom of shell midden 

Deterioration:

PEG TREATMENT% MW: 50% Carbowax (PEG) 1500  in water.   Duration: No mention of timeHeated? No 

Drying: No mention of drying technique, likely air-dried.

(Sprague 1976)

(Note:  PEG 1500 used in treatment may now be 540 Blend due to name change in mid 70’s)

2010: Basketry has a dry brown appearance.  Materials are delicate with little flexibility.
Site: Fishtown (45 SK 99)Date recovered/treatment: 1974Location of Collections: Swinomish Indian Tribal CommunityMaterials: species IDs has not yet been performed

Age of Collections:1220 years old +/- 70 years

Burial conditions:  water-saturated anaerobic deposits 

Deterioration:

PEG TREATMENT % MW: 50% polyethylene glycol 1500 in water Duration: 4 weeksHeated? No 

Drying: Air-dried. 

(Blukis Onat 1976)

(Note:  PEG 1500 used in treatment may now be 540 Blend due to name change in mid 70’s)

2009: Request to examine collections respectfully declined due to lack of protocol in collections policy.
Site: Glenrose Cannery Site (DgRr 6)Date recovered/treatment: recovered 1988 & 1990, treated in 1991Location of Collections: LoA at UBCMaterials: collection contains cherry/maple bark; fir-wood splints (Abies) and cherry/maple bark (true bark) with cedar splint elements and salmonberrty element.  IDs by M-L Florian (reported in Eldridge 1991)

Age: 4300 BP

Burial Conditions: water saturated anaerobic deposits in Fraser estuary; deposit lies just underneath beach pebbles, consists of layers of grey and coarse sand with crushed shell. (Bernick1991) 

Deterioration:

PEG TREATMENT % MW: 10-20% aqueous soln of PEG (no MW recorded), but possibly PEG 540 Blend Duration: (no time recorded). Heated?: No 

Drying: Possibly freeze dried and consolidated with Rhoplex 33. 

(Erling 1991)

1991:“basketry is waxy and generally dark-colored” (Bernick 1991, pg 119)2010: To date the authors have not examined the basketry material from this site.
Site: Hesquiat Harbor ( ) Date recovered/treatment: Location of Collections:  RBCMMaterials: wood splint baskets

Age: 100-200 years 

Burial conditions:

Deterioration: materials removed damp not waterlogged.

AIR DRIED  
Site: Hoko Complex (45 CA 213)Date recovered/treatment: began in 1973Location of Collections: Makah Cultural and Research CenterMaterials: limb, inner bark, no reference found identifying species 

Age: 2500 year old fishing camp (Croes 1976, pg 88) 

Burial conditions:  anaerobic desposits along riverbank, Hoko River estuary 

Deterioration:

PEG TREATMENT Artifacts recovered in 1967- 50% white glue treatment.% MW: Artifacts recovered in 1973—treated with 50% PEG 1500Duration: 4 weeks

Heated? No

Drying: Air dried

(Croes 1976)

(Note:  PEG 1500 used in treatment may now be 540 Blend due to name change in mid 70’s)

2009: While most of the Hoko River materials seem darkened by not waxy the artifacts do range visually from dry (315/AL/4 ) to saturated/waxy surfaces (ACQ 910909). 
Site: Kanaka Creek basket  Date recovered/treatment: 1991Location of Collections:  Museum of Archaeology and Ethnology, Simon Fraser University (1992.004.001)Materials: cedar root (Winter 2010)

Age:  

Burial conditions: fine grained fluvial deposits on the north bank of the Fraser River. A large lump of silty sand coated and supported the basket.

Deterioration:

PEG TREATMENTArtifacts were rinsed to remove mud and silt, then% MW: 20% PEG 400 for 15 weeks then 6 months of 20% PEG 400 + 4% PEG 4000Duration: 9.5 months

Heated? No

Drying: Air dried, then couriered to CCI where it was freeze-dried.

2010:
Site: Lachane Site (GbTo 33)Date recovered/treatment: 1973 Location of Collections: Canadian Museum of Civilization, Gatineau, QuebecMaterials:  26 baskets are cedar bark, 1 is “inner alder bark” (Croes 1989)  

Age: 1600-2500 BP

Burial conditions: watersaturated anaerobic deposits; matrix resmbled peat (Inglis 1976) 

Deterioration:

PEG TREATMENT % MW: 10% PEG 1500 for three months, 25% PEG 1500 for three months, 50% PEG 1500 for three monthsDuration: Nine months Heated? No 

Drying: No mention of drying technique, likely air-dried

(Inglis 1976)

(Note:  PEG 1500 used in treatment may now be 540 Blend due to name change in mid 70’s)

2010: To date the authors have not examined the basketry material from this site.
Site: Little Qualicum River Site (DiSc 1)Date recovered/treatment: 1972?, 1974,1976 Location of Collections: RBCM Materials: western red cedar (all 21 basketry artifacts, all fragmentary): Some are entirely cedar bark, some entirely withe splints, some a combination.  Species IDs by K. Bernick (Bernick 1983).

Age: ca. 1000 BP

Burial Conditions:  See Stratigraphy description in Bernick 1983  (possibly A site catchment analysis of the Little Qualicum River site, DiSc 1, a wet site on the east coast of Vancouver Island, B.C.?) 

Deterioration:

1972 treatments: look for records at RBCM- possibly not PEG treatments.PEG TREATMENT% MW: 50% PEG 1500  Duration: 2 months.

Heated? No 

Drying: Air Dried.

(Simonsen 1976)

(Note: PEG 1500 used in treatment may now be 540 Blend due to name change in mid 70’s)

2010: To date the authors have not examined the basketry material from this site.(Would be interesting to view since possibly two different treatments performed on materials).
Site: Montana Creek  (49-JUN-453)Date recovered/treatment: 1989-1991 Location of Collections: exhibit, Juneau-Douglas City MuseumMaterials: Hemlock and spruce wood with split basketry-like spruce root lashings

Age: 400-600 BP 

Burial Conditions: eroding river bank with high iron content sediment, small pebbles and sand (Loring, Jon 1995)

Deterioration: Thought to have little deterioration

PEG TREATMENT% MW: 10% PEG 200, 5% PEG 1000 and 10% Carbowax Compound 20M (average mw 15,000-20,000) Duration: several months Heated? No 

Drying: Air-Dried

2005: Tan color, not shiny or waxy, no observable distortion, rather brittle (Carrlee, 2005)2009: Artifact appears stable. 
Site: Mud Bay (Qwu? Gwes) (45TN240)Date recovered/treatment: began 2000- ongoingLocation of Collections: Squaxin Island Tribe’s Museum Library and ResearchMaterials: western red cedar inner bark, maple inner bark, cedar with and root.

Age: ~500 

Burial Conditions:

Deterioration:

 

PEG TREATMENT: LONG% MW: 50% PEG 400 Duration: 4 months. Heated? No 

Drying: Air-dried

(Standard treatment of lab at South Puget Sound Community College as described in Croes, Fagan, Zehender 2008)

2007, 2008, 2009:  Requests to examine collections and learn about the materials unanswered.
Site: Munk Creek (45SK156)Date recovered/treatment:  Location of Collections: Swinomish Indian Tribal CommunityMaterials: No reference found identifying material types or species

Age: ca. 1000 AD (radiocarbon dated) 

Burial Conditions:  found buried in riverbank/channel   

Deterioration:

Not available at the time of publication. 2009: Request to examine collections denied at this time due to lack of protocol in collections policy.
Site: Musqueam East Site (DhRt 2) Date recovered/treatment: 1959;1974 / 1974-75 Location of Collections: LoA at UBCMaterials: No reference found identifying material types or species

Age:

Burial Conditions:  “blue Fraser River clay” (Bernick 1991)

Deterioration:

1959 artifact air dried.1974-75 pieces treated with polyethylene glycol.PEG TREATMENT% MW: 50% PEG (MW of PEG unknown at this time)

Duration: 4 months 

Heated? No

Drying:  Air dried

(Bernick 1991)

1991: 1974 finds pliable, waxy and dark coloured; 1959 find encrusted with mud, brittle, broken, frayed (Bernick 1991)2010: To date the authors have not examined the basketry material from this site. Requests in 2008 and 2009 to the Musquem Band for permission to examine and possibly sample material from the collection were unanswered.
Site: Musqueam Northeast (DhRt 4) Date recovered/treatment: 1973 & 1974/1973-1975Location of Collections: LoA at UBCMaterials: western red cedar withe/root  (Archer and Bernick 1990) 

Age: ca. 3000 BP

Burial Conditions: Artifacts present in two superimposed matrices: lower layer— dense silty-sandy clay, upper stratum: dark, soft silty clay (Bernick 1991). Anaerobic.  Below the water table.  Capped by stratified shell midden and above that Fraser River alluvium.  Layers with basketry about 2 m below modern surface; likely deposited in a shallow/marshy creek originally.

Deterioration:

PEG TREATMENT: MID-LONG% MW: immersed in 50% PEG 1500 Duration: 2.5-4 monthsHeated? No 

Drying: Air dried

(Note: the PEG 1500 may what we now consider 540 Blend due to name change in mid 70’s)

Staff anecdotal comments- weeping.1991“Most items are pliable and appear to be in relatively good condition…” (Bernick 1991)2010: To date the authors have not examined the basketry material from this site. Requests in 2008 and 2009 to the Musquem Band for permission to examine and possibly sample material from the collection were unanswered.
Site: Old Songhees Reserve (DcRu 25)  Date recovered/treatment: 1994Location of Collections:  RBCMMaterials: possibly yellow cedar inner bark,  western red cedar inner bark and spruce root

Age: ~150 years old. 

Burial conditions:

Deterioration:

Currently undergoing treatment at CCI. 2010:
Site Pitt River Site (DhRq 21) Date recovered/treatment: 1980Location of Collections: RBCM Materials: western red cedar splints (Bernick 1981)

Age: ca. 3000 BP 

Burial Conditions: anaerobic alluvial deposits below the water table,; basketry was in unconsolidated silty clay, 1.2 m below modern surface, likely a slough when originally deposited.   

Deterioration:

SOLVENTWoven artifact materials recovered were gently washed to removed soil and then slowly dehydrated ethanol and dried under restraint. (Bernick 1991) 1991: rigid and brittle (Bernick 1991)2010: To date the authors have not examined the basketry material from this site.
Site: Ozette (45 CA 24) Date recovered/treatment: 1970’s Location of Collections: Neah Bay, Makah Cultural and Research Center Materials: western red cedar inner bark, limb, root

Age: 450 BP or younger   

Burial Conditions: pH of 5.5-6 in 1970, water entering midden pH6 (Grosso 1976, vol 2, page 22)

Deterioration:

PEG TREATMENT% MW: 50% Carbowax in water with anti fungal agent Cytox 2013 (Gleeson and Grosso 1976)Duration: 4 weeksHeated? No 

Drying:  Air dried

(Note: the PEG 1500 may what we now consider 540 Blend due to name change in mid 70’s)

1990: Artifacts dark brown to black with layer of excess PEG on surface.  Artifacts are stable. (Cooke and Cooke 1990)2009: While published reports and lab notes indicate that these pieces were all treated the same way the outcome is varied.  All of the materials are preserved.  However some are dry and medium brown in appearance, others dark brown, still others dark with a matte waxy surface, and a few with a wet shiny appearance.  While variation may be due to difference in material types it is interesting to note that hats containing both root and inner bark have same appearance.  Thicker splint pieces are lighter in color and drier in appearance.
Site: Scowlitz (DhR1-16W) Date recovered/treatment: 1992-1993/ 1993-1994 Location of Collections: temporarily at LoA at UBC Materials: western red cedar wood splints, IDs by K. Bernick (REF: Bernick 1994) 

Age: ca. 1200 BP 

Burial Conditions:  anaerobic alluvial desposits in riverbank, apparently originally deposited elsewhere and washed into that location in antiquity.  Specifically: in a 50-cm-thick layer of orange-mottled grey muddy sand pH=4.9, overlain by 20-cm-thick blue-grey sandy mud pH=3.5; and above that 15-cm-thick loosely packed sandy mudd pH 1.7.  Bottom of the sequence (under the matrix with the baskets) was angular rocks.  Completely inundated seasonally.   

Deterioration:  “remarkably weak and in an advanced state of decomposition relative to similar material from other known sites in the region” when recovered, extensively infiltrated with rootlets (Bernick 1994) 

PEG TREATMENTTwo treatment techniques used:% MW: Baskets A and B: immersed in 20% PEG 400 in water then 6 months in 20% PEG 400 and 4% PEG 4000 (3350 in US) in waterNumbered fragments: 4 months in 20% PEG 400 in water

Heated? No 

Drying: frozen, freeze-dried, then treated with Parylene to consolidate surface.

(Conservation Treatment Records from CCI at LoA and Grant 1996)

2009: All materials appear fairly stable.  Materials have light brown, dry appearance. Very few loose bits exist in storage containers, possibly indicated stability.  Elements appear to have minor flexibility.
Site: Seymour Inlet ( ) Date recovered/treatment: Location of Collections: RBCMMaterials: wood splint baskets

Age: est.100-200 years old. 

Burial conditions:

Deterioration: materials damp not waterlogged when found. (Bernick 2010)

Air Dried. 2010:
Site: South Baranof Island (49-XPA-78)Date recovered/treatment: 1995 Location of Collections: Alaska State MuseumMaterials:  possibly hemlock or spruce by ML Florian;

Age: 4510 +/; 60 uncal BP  (cal 3350-3100 BC) 

Burial Conditions: water-saturated dark brown clayey silt, intertidal stream bank; original depositional topography uncertain, likely affected by tectonic uplift 

Deterioration: Moderate to very deteriorated?

 

 

PEG TREATMENT% MW: 20% PEG 400 and 5% PEG 4000 Duration: 6 monthsHeated? no 

Drying: Non-vacuum freezer

(ASM treatment records)

2009: Surface is dry, brown.  Flexible, almost spongy softness.  Texture of fibers evident on surface.  Too delicate for exhibition or travel.
Site: Sunken Village (35 MU 4) Date recovered/treatment: 2006/07 Location of Collections: University of Oregon Oregon State Museum ?Materials: cherry bark, western red cedar

Age: 500-700 years old (1400-1450 AD) 

Burial Conditions: in anaerobic alluvium on river bank (tidal)

Deterioration:

PEG TREATMENT% MW: 50% PEG 400 Duration: at least four months of impregnationHeated? No 

Drying:  Air Dried

(Croes, Fagan, Zehender 2008)

2010: To date the authors have not examined the basketry material from this site.  Collection materials moved to Oregon State Museum at University of Oregon in Fall 2009.
Site: Tawah Creek (49-YAK-019)Date recovered/treatment: 2004 Location of Collections: Alaska State MuseumMaterials: possibly spruce root

Age: possibly 130 years old (weir at site was dated)

Burial Conditions:

Deterioration: Moderate deterioration?

 

PEG TREATMENT% MW: 50% PEG 540 Duration: over 1 month Heated? 60 degree C oven 

Drying: non-vacuum freezer.

 (ASM treatment records)

2009: Appears stable, edges need consolidation from physical unraveling because basket has stress from its three- dimensional shape.  Has been stored in stable environment for past two years.
Site: Thorne River  (49-CRG-433)Date recovered/treatment: 1994 Location of Collections: Alaska State MuseumMaterials: root (spruce—possibly hemlock?)

Age: 3450 BCE, (5450 years old carbon 14 dating +/-)

Burial Conditions:

Deterioration: Moderate to very deteriorated?

 

PEG TREATMENT% MW: 20% PEG 400 and 5% PEG 4000 Duration: 6 months Heated? No 

Drying: non-vacuum freezer.

(ASM treatment records)

2009: Basket is mostly in one large piece and is stabilized from deterioration.  Appearance is good, but it is too fragile for exhibit or travel. Dry, flexible, spongy. 
Site: Wapato Creek (45 PI 47)Date recovered/treatment:Location of Collections: Burke Museum, Materials: western red cedar inner bark 

Age: 340 

Burial Conditions: in 2-m-deep anaerobic alluvial deposits that were covered by 2+ m of industrial fill (Munsell 1976)  

Deterioration:

PEG TREATMENTPlaced in Ethanol for two days (to reduce trapped H2O between fibers and facilitate PEG exchange) % MW: 50% PEG 1000 Duration: 2-4 days 

Heated? No 

Drying: dry on racks (1-2 weeks)

 (Munsell 1976)

2006: hat appeared dry and brittle but stable. 2010: Piece has safely traveled for exhibit for two years.
Site: Water Hazard (DgRs 30)Date recovered/treatment: 1988/1989 treatment Location of Collections: LoA at UBCMaterials: western red cedar wood splints and inner bark.  One may have yew components and another hemlock. (by Jack Gray in Bernick 1989)

Age: 1700 BP 

Burial Conditions: below watertable in anaerobic Fraser delta sediments; about 2 m below present surface; likely originally desposited in a slough or salt marsh (recovered from backhoe spoil piles ergo matrix it was in uncertain but appears to have been near interface of sandy matrix with pH 6.8 and “blue-grey silty clay” pH 6.2—Bernick 1989:30).  

Deterioration: 

PEG TREATMENT% MW: PEG 540 Blend, concentration unknown.  Duration: 4 weeks Heated? No 

Drying: Freeze dried

(Erling 1989)

2009: Artifacts appear stable.  No evidence of weeping.  Also appear to have some flexibility—but not much.  Splin fragments more flexible than inner bark.
Site: Yakutat  Date recovered/treatment: Location of Collections:  possibly at Forest Service Office, SitkaMaterials:

Age:  

Burial conditions:

Deterioration:

Treated with Silicon Oil treatment at Texas A&M 2010:

 


[1] Royal British Columbia Museum

[2] Laboratory of Archaeology of University of British Columbia

[3] Thomas Burke Memorial Washington State Museum


High Molecular Weight PEG for Basketry

July 17, 2009

 

Introduction: PEG treatments for waterlogged archaeological basketry at the Alaska State Museum and published treatments for such basketry suggest that use of mostly low molecular weight PEG was not enough to impart the stability needed for study and exhibition.  This experiment investigated the use of various concentrations of high molecular weight PEG.  Testing included impregnation in both room-temperature solutions and solutions kept in a 60degree F oven.  Informed by these results, the Alaska State Musuem decided to proceed with treatment using 55% PEG 3350.

Catalog No:  95-12-6

Object: Basketry fragments

Culture:  Northwest Coast Native, possibly Tlingit.

 Description:  Sixteen samples from 95-12-6, a large group of approximately 300 fragments (mostly knots.)  Artifact described by archaeologists as spruce root webbing or semi-rigid netting.  Reconstruction of this artifact is unlikely, and the large number of similar small fragments give good comparative study samples.  Material is most likely spruce root.

49XPA78-4green

 

 

 

 

 

 

49XPA78-4tiny

 

 

 

 

 

 

ASM 95-12-6 semi-rigid knotted netting

ASM 95-12-6 semi-rigid knotted netting

 

 

 

 

 

 

 

 

Condition:  All fragments stored in distilled water in a refrigerator since their discovery in 1995. Biological growth has occurred in the past. Water was rarely changed. Since 2006, little biological growth has been noted. All fragments are fragile.

Background/ Reason for Report:  Found on South Baranof Island in 1995.  Another basket from this site, 95-12-1, was already treated.  It was C-14 dated at 4,450 years BP and the material was (with some controversy) identified as hemlock and not spruce root.  20% PEG 400 and 5% PEG 4000 was the protocol used by the ASM to treat 95-12-1 as well as the ancient Thorne River spruce root basket from a different site.  The physical appearance of both those treated baskets is pleasing, but they are still too fragile to be exhibited or handled easily.  They are very flexible and shed fibers readily.  Perhaps the PEG concentrations were too conservative?  This experiment intends to test the theory that an increased amount of higher molecular weight PEG might yield better results.

PROPERTIES OF PEG

Low molecular weight PEG (PEG 200-600) is thought to penetrate more deeply into the secondary cell wall and the smaller spaces in the wood than higher molecular weight PEG.  It is also more mobile and hygroscopic.  If too much is used, the surface will look wet, feel soft, attract dust, and be humidity-sensitive.  High molecular weight PEG (PEG 1500-6000) does not penetrate the secondary cell wall because the molecule is too large, but it acts like a filler, impregnating the lumens and interstices between the cells.  Addition of higher molecular weight PEG is thought to be helpful if the wood is more degraded.  Too much high molecular weight PEG can leave white crusts on the surface, result in a heavy artifact, and be harder to dry.  A combination of high and low molecular weights of PEG is often the solution, but it can be tricky to determine the right mixture for solid wood, and basketry is even more challenging.  Higher molecular weight PEG is thought to cause damage if used on wood with fairly intact cell wall structure, perhaps from the force as the hygroscopic PEG pulls water out of the smaller structures where the PEG molecule cannot penetrate? (Astrup 1994, Grattan 1996.)

Low mw PEG is a liquid, and high mw PEG is a solid powder

Low mw PEG is a liquid, and high mw PEG is a solid powder

 

 

 

 

 

 

 

 

 

HEATING

PEG 540 blend was used in the ASM lab on the Tawah Creek basket at 50% concentration for a month at 60°C in the lab oven with good results.  Heating may speed and enhance penetration as well as the solubility of high molecular weight PEG (Grattan and Clark 1987.)  However, heating was thought to contribute to undesirable darkening for the objects treated at the Ozette site (Cooke, Cooke and Grattan 1993.)  Heat is an accelerant to deterioration and PEG treatments for leather in the literature have mostly eliminated heat altogether for that reason.  Heat is also thought to break down the PEG molecule, and some sources have suggested not heating PEG during the impregnation (Bilz et al 1994.)  Since most of our fragments are small enough to put in the oven, it would be worth knowing if heating provides an advantage. 

Goals of Treatment:  The treatment for these 16 fragments will give data that will set the protocol for stabilization treatment of the other waterlogged basketry fragments in group 95-12.  Several variables affect PEG treatment: deterioration of the wood, species of wood, anatomical structure of the wood (bark, trunk, root etc,) concentration of PEG used, molecular weight of PEG used, duration of soaking, and heating during impregnation.  The proposal aims to address the following questions:

  1. Can we develop a PEG protocol that will make the waterlogged artifacts stable enough for study and exhibition?
  2. What are the optimum concentrations of PEG for this basketry?
  3. What are the optimum molecular weights of PEG for this basketry?
  4. Will increasing the amount of high molecular weight PEG specifically help?
  5. Does heating during treatment provide a benefit?
  6. Will the treated artifact be vulnerable to high humidity?

Stabilization will prevent ongoing deterioration and allow future study and exhibit as part of the permanent collection.  After treatment, additional research into adhesives for mending broken fragments may be undertaken.  The results of the PEG basketry treatments here over the past 15 years would be of interest to the conservation field and should probably be published.  There is very little in the conservation literature about successful treatment of waterlogged basketry.  Additional consolidation of the two ancient baskets already treated in the collection is needed for added stability, which might be achievable with nebulizer mist application.  Adhesives and consolidants will be explored in separate future treatment proposals.

Sample knot, waterlogged, before treatment

Sample knot, waterlogged, before treatment

 

 

 

 

 

 

 

 

 Treatment Methodology and Rationale:  Samples fell into three main groups.  Each group had five fragments treated with various concentrations and molecular weights:

1. Samples treated at room temperature

2. Samples treated at 60°C

3. Samples treated briefly at 160°C and then at 60°C.  (This grouping was the result of an error that led the samples to be overheated for approximately 12 hours.)

20% PEG 400, then 20% PEG 3350

Rationale: PEG 400 will enter the secondary cell wall and bond there, while the 3350 will fill in the larger voids and give strength.  This is slightly higher than the concentration of 3350 PEG used previously in the lab, but those examples did not give enough strength. PEG 400 is kept at 20% to hopefully prevent excess from oozing out.

20% PEG 400, then 35% PEG 3350

Rationale: High molecular weight PEG is supposed to perform well on highly degraded wood.  Our basketry is very old and treatment with mostly low molecular weight PEG was not fully successful.  This suggests the basketry may be more degraded than predicted, and may respond better to high molecular weight PEG.

20% PEG 400, then 55% PEG 3350

Rationale: Some references suggest avoiding the eutectic, but others (Jensen et al 2000) seem to suggest that aiming for the eutectic is desirable.  Theoretically, ice crystals form in a way that blocks even distribution of the PEG unless the eutectic is used.  Apparently, concentrations lower than the eutectic also expand on freezing, causing cracks.  At the eutectic, the 9% expansion of ice is counterbalanced by 7% volumetric contraction of PEG.  A medieval log house in Oslo was treated successfully with 50-55% PEG 4000 (Astrup 1994.)  The successful Tawah Creek basket treatment by Scott Carrlee (unpublished, Alaska State Museum) used PEG 540 near the eutectic.

55% PEG 3350 alone 

Rationale: Since the Jensen et al article (2000) seems to suggest PEG near the eutectic is optimal even though other articles specifically indicate the opposite, it would be worthwhile to isolate the PEG 3350 to test this.  Perhaps it simplifies the phase diagram to only use one molecular weight of PEG.  Astrup (1994) and Hoffman (1990) found some success with 50% PEG 4000 in degraded softwoods.

20% PEG 400, then 75% PEG 3500 

Rationale: Several sources report success with high concentrations of high molecular weight PEG for highly degraded wood (DeWitte et al 1984, Kaenel 1994.)

7mesh

 

 

 

 

 

 

 

 

Fragments of similar size with no obvious joins to other fragments were selected for testing and photographed.  Each sample was sewn between layers of nylon mesh screening with polyester thread to hold the fragment securely, allow good circulation around the fragment, and permit handling.  Each PEG concentration was increased incrementally approximately every two weeks.  PEG 400 was increased in 5% increments, PEG 3350 was increased either 5 or 10% increments.  In each case, the concentrations were increased gradually to minimize the risk of osmotic shock from pressure differentials between the fluid inside the fragile wood and the fluid in the container.  The time to reach desired concentration took between 3 and 6 months.  PEG 3350 was supplied as a powder and was dissolved in a bit of the test solution using a hotplate before adding it to the unheated and heated sample containers.  For the unheated samples, the addition of the warm PEG 3350 caused them to be cloudy for two to three minutes before becoming clear again.  All samples were removed from solution at the same time.  Each sample was rinsed in a beaker of distilled water to rinse excess PEG from the surface and gently tamped with KimWipes to remove as much water as possible before freezing.  Fragments were weighed and placed in the freezer (-35°C) to drive off the excess water through sublimation (solid ice directly to water vapor.)  Air drying without the freezer would send liquid water to water vapor, and the strong surface tension of the liquid water contributes to collapse of cell structure as the water evaporates.  Samples were regularly weighed to determine the end point of drying (when weight no longer decreased,) and fragments were all removed at the same time.  After removal from the freezer, fragments were taken out of the nylon mesh and photographed on graph paper while still cold.  They were photographed on graph paper again a week later to check for possible distortion from the evaporation of residual water at room temperature (none observed.)  A month after they were removed from the freezer, they were subjected to 80% humidity for 12 hours. 

 7G

7grid

 

 

 

 

 

 

 
Front and back of fragment cold out of freezer, and here fully dry

Front and back of fragment cold out of freezer, and here fully dry

 

 

 

 

 

 

 

 

 

Results and Interpretation: While waterlogged, the wood was dark brown in color.  After treatment, the room temperature samples all turned out very pale beige-gray driftwood-like color, with no obvious color difference with higher concentrations.  60°C oven samples were all pale yellow ochre-grayish in color, but still much paler than most historical basketry.  160°C overheated samples were a rich brown burnt umber color, ironically more like historical spruce root basketry in color, and the higher concentrations were darker.  The untreated air-dried control sample was the darkest of all (dark burnt umber) and extremely brittle, shrunken, and deformed.  Almost all samples had some whitish powdery PEG residue/crusts in the crevices, and this did not seem to increase with concentration, but it was more pronounced on the samples impregnated at room temperature.  The waxy PEG could not easily be brushed from the surface (the brush tended to drag it around) but localized application of ethanol with a brush under magnification seemed to drive the PEG below the surface and improved the appearance.  All impregnated samples were placed in the humidity chamber and raised to 80% RH for 12 hours to evaluate effect of high RH on the concentrations and molecular weights of PEG used.  No oozing or surface changes were observed on the samples or on the blotter paper below them.  While the Alaska State Museum has stable RH, there are less stable locations in Alaska that may wish to exhibit the artifacts after treatment.

 

UPDATE: From a suggestion by Dana Senge, I repeated the RH test.  The 75% concentrations of the unheated and the overheated samples both oozed, and their surfaces got very dark and waxy.  This did not revert back upon stabilization of the RH, and did not seem to get worse with repeated RH tests.  The heated 75% sample did not ooze or get dark, even on repeated RH fluctuations.

 

Himdity test at 80% RH

Humdity test at 80% RH

 

 

 

 

 

 

 

 

20% PEG 400, 20% PEG 3350

Room Temperature: Weight loss stabilized after 20 days in the freezer, sample lost 22% of its wet weight

Heated: 65 days, lost 22%

Overheated: 40 days, lost 33%

20% PEG 400, 35% PEG 3350

Room Temperature: 40 days, lost 23%

Heated: 90 days, lost 21% 

Overheated: 40 days, lost 25% 

20% PEG 400, 55% PEG 3350

Room Temperature: 65 days, lost 23%

Heated: 90 days, lost 23%

Overheated: 20 days, lost 22% 

55% PEG 3350 

Room Temperature: 90 days, lost 23%

Heated: 65 days, lost 18% 

Overheated: 20 days, lost 22% 

20% PEG 400, 75% PEG 3350 

Room Temperature: 90 days, lost 20% 

Heated: 20 days, lost 10% 

Overheated: 65 days, lost 18% 

Samples after treatment: unheated rather gray, overheated brown, heated yellowish.  Control in upper corner

Samples after treatment: unheated rather gray, overheated brown, heated yellowish. Control in upper corner

 

 

 

 

 

 

 

 

 

Assumptions: a lower percent weight loss during drying means less water was lost and there was less water to lose in the first place because it had been replaced by PEG.  If this is true, all the room temperature fragments had about the same amount of water loss, and therefore a similar amount of PEG penetration.  But at higher concentrations, the heated fragments had less water loss, and thus better penetration of PEG 3350 than the room temperature samples.   Explanations could include better penetration of molecules that may have some size variation through thermal breakdown, better diffusion, possible expansion of wood structure with heat to allow better penetration, or the enhanced solubility of heated PEG (Grattan and Clark 1987.)

The samples with lowest concentrations were distinctly spongier to the touch than those with 55% 3350 and higher, in spite of similar amounts of weight loss.  Surprisingly, results for 20% PEG 400 with 55% PEG 3350 were the same as the results for 55 % 3350 alone. 

Flaws: I may be misinterpreting the Jessup et al (2000) article about the eutectic.  Varying geometry of the shape of the knots made my qualitative comparisons about flexibility and brittleness too subjective.  Sample size was not statistically significant.  Have not done cobalt thiocyanate staining to see which samples have more PEG in them under microscopic examination.   Determining degree of deterioration from the molecular weight of PEG that works is a backwards method.  I began an experiment in July 2009 to try to determine the moisture content of the archaeological basketry compared to historical basketry samples waterlogged artificially in the lab.  Also need to spend some time examining the samples structurally under the microscope.

Conclusions:  The idea that high molecular weight PEG around 55% concentration is useful for highly degraded softwoods is in harmony with the conclusions found by others (Astrup 1994 and Hoffmann 1990.)  The superior performance of the heated 75% solution was based on a single fragment losing a total of only 0.1g of water in the freezer after only 20 days.  Could this be an anomaly?  If 55% PEG 3350 does not give adequate stability for the first basket I treat, I may attempt the higher concentration.  The oozing of the 75% fragments at room temp and with voerheating makes me nervous.

Annotated Bibliography:

Astrup, E.E. “A Medieval Log House in Oslo – Conservation of Waterlogged Softwoods with Polyethylene Glycol.”  Proceedings of the 5th ICOM Group on Wet Organic Archaeological Materials Conference, Portland, Maine. 16- 2- August 1993.  Pub 1994 pp 41-50

Ellen Carrlee’s Notes: Wood was identified as pine (Pinus silvestris) and spruce (Picea abies).  For both highly degraded and less degraded softwoods, 50-55% PEG 4000 was most useful.  She heated at 60°C adding 10% every 8 weeks.  She was getting 3-5 % shrinkage in the 50-55% range, but more above and below it.  Waterlogged wood is already somewhat swollen, however.  Results similar to Hoffmann’s 1990 article on softwoods.  Wood with fairly intact cell wall structure might suffer from shrinkage with low mw PEG alone, perhaps the hygroscopic PEG pulls the water out of tyhe small spaces the molecule cannot fir into?  Mentions that the two-step method is really intended for wood like oak that tends to have areas of both low and high degredation.

Barbour, R.J. and L. Leney.  “Shrinkage and Collapse in Waterlogged Archaeological Wood: Contribution III Hoko River Series.  In book. Proceedings of the ICOM Waterlogged Wood Working Group conference: Ottawa, 15-18 September 1981. ICOM Waterlogged Wood Working Group (1982), pp. 209-225.

Ellen Carrlee’s notes: Shrinkage from capillary tension happens when the free water is pulled by evaporation from the void structure of the wood.  Shrinkage is also caused from desorption of bound water from the cell wall.  Article gives extensive info about which cells collapse in which direction.

Bilz, Malcolm, Lesley Dean, David W. Grattan, J. Clifford McCawley, and Leslie McMillen.  “A Study of the Thermal Breakdown of Polyethylene Glycol.”  Proceedings of the 5th ICOM Group on Wet Organic Archaeological Materials Conference.  Portland, Maine. 1993.  Ed Per Hoffmann.  1994.

Ellen Carrlee’s Notes: PEG from ten year old artifact did not decrease in molecular weight.  Keeping oxygen or air out slows PEG degradation.  Thermal aging increases PEG degradation.  Slightly more degradation of PEG 3350 in presence of iron salts, but not so much with PEG 200.  Less degradation of PEG 3350 in oak than by itself.  BHA (not very soluble in water) helps reduce oxidation degradation of PEG 3350; propyl gallate does not, and also forms colored complexes with iron.  No degradation of PEG with natural aging either in artifacts or by itself.  Impregnation should take place at room temperature to avoid degradation.  Store PEG at its most concentrated.  PEG is reasonably reversible and can be leached from artifacts.  Lower concentrations of PEG 400 (below 40%) oxidize more.  In degradation, are we getting smaller molecules, do they go into the wood, or do they evaporate? 

Cooke, Vincent, Deborah Cooke, and David W. Grattan.  “Reversing Old PEG Treatments of Objects from the Ozette Site.”  Proceedings from the 5th ICOM Group on Wet Organic Archaeological Materials Conference, Portland, Maine 16-20 August. 1993. 1994. pg 92-109

Ellen Carrlee’s notes: Treated with PEG 540 blend c. 1973, hygroscopic, dark, heat used.  Extracted PEG, retreated with 2-step PEG 200 at 15% for 40 days, and PEG 3350 at 9.5% for 20 days, then freeze dried.  Acetone Rosin was found irreversible.  They also consolidated with Polyox 2.5%.

Cook, Clifford and David Grattan.  “A Method of Calculating the Concentration of PEG for waterlogged Wood.”  Proceedings of the 4th ICOM Group on Wet Organic Archaeological Materials.  Bremerhaven 1990.

Ellen Carrlee’s notes: Liquid grade, such as PEG 200 is used to control cell wall shrinkage and waxy solid PEG 3350 is used to give some structural strength to the wood.  Important to know:

  1. Wood species
  2. Actual density of the wood
  3. The normal density of undeteriorated wood
  4. The Moisture content at the fiber saturation point of the undeteriorated wood.

These are the parameters used by PEGCON.  Lower MW PEG such as PEG 200-600 penetrate into the cell wall better than higher MW.  Higher MW PEG is meant to fill in the lumens and has been shown to work better on very deteriorated wood.  Too much PEG 400 results in weeping , soft, humidity-sensitive wood.

Too much PEG 3350 results in heavy wood, harder to dry. Umax is the maximum moisture content, increases with deterioration.  Some woods have a higher Umax naturally than others, so that’s why you have to know the species.  Over 55% PEG mixture might not freeze in the drying process.

Christensen, B. Brorson.  The Conservation of Waterlogged Wood in the National Museum of Denmark.  National Museum of Denmark, Copenhagen, 1970. 

Ellen Carrlee’s notes: Includes history of treatments 1859-1962, and reports on work thusfar on Viking ships from Roskilde Fjord.   Includes PEG 4000 in various solvents but having difficulty with the issue of oak penetration.  Methylene chloride is the best solvent for removing PEG after treatment.  Water is too slow and results in too much rubbing which obscures fine details and rounds sharp edges.  Cold treatment with PEG 4000 as opposed to warm treatment resulted in less collapse of the oak.  Began with 25% and increased to 50% for a year total

DeWitte, Eddy, Alfred Terfve, Jozef Vynckier.  “The Consolidation of the Waterlogged Wood from the Gallo-Roman Boats of Pommeroeul.”  Studies in Conservation Vol 20 no 2 1984.  pp 77-83

Ellen Carrlee’s notes: PEG impregnation with PEG 4000 up to 85% heated to 65C in a steel tank.  Oak with no solid core.

Florian, Mary-Lou and Richard Renshaw-Beauchamp.  “Anomalous Wood Structure: A Reason for Failure of PEG in Freeze-Drying Treatments of Some Waterlogged Wood from the Ozette Site.”  Proceedings of the ICOM Waterlogged Wood Working Group Conference Ottawa 1981. pub 1982 pp. 85-98 

Ellen Carrlee’s notes: Factors that decrease the penetration of the PEG include:

  • Few and small hardwood cells
  • Inclusions (gum and tyloses) in hardwood vessels
  • Abundant hardwood thick walled fiber cells
  • Short soft wood longitudinal tracheids
  • Absence of ray tracheids
  • Absence of radial and longitudinal resin canals
  • Aspirated and encrusted bordered pits
  • Blind simple pits
  • High specific gravity
  • Ray parenchyma containing resin or extraneous material
  • Reduced tangential wall pitting
  • Extractives in heartwood

Picea sp. (spruces) and Thuja pliacata (Western red cedar) have no tangential permeability due to little tangential wall pitting, blind pits, and resin in the ray parenchyma cells.  Spruce more permeable than red cedar due to resin canals and ray tracheids.  Cedar is vulnerable to collapse of radial walls of the tracheids.  In some woods, large thin-walled early wood tracheids adjacent to thick walled later wood tracheids can collapse and cause uneven grain appearance.  In this case, spruce showed this result.  Roots have many parenchyma cells and can have excessive longitudinal shrinkage.  List of history-chemical tests given.  Many softwoods samples show open enlarged tracheid bordered pits which make the wood abnormally porous. 

Grant, Tara and Malcolm Bilz.  “Conservation of Waterlogged Cedar Basketry and Cordage.”  Proceedings of the 6th ICOM Group on Wet Organic Archaeological Materials York, 1996.

Ellen Carrlee’s notes: Parylene coating on cedar “bark” baskets from Scowlitz site (500-1200 years old)  treated with modified PEG treatment. 20% PEG 400 for 3 months and then freeze-dried.  Came out still too fragile.  Parylene is irreversible but worked well.  Need a special vacuum pyrolysis chamber to apply it.  NOTE: Bilz reported at the 11th ICOM-CC Triennial in Edinburgh Sept. 1996  that further study of Parylene shows that it does not age as well as they thought and it is not recommended for long term conservation.  Also, personal communication with Kathryn Bernick (April 9, 2009) she mentions that the Scowlitz baskets are all made of cedar withes (wood splints) and not bark.  Some of the cordage was indeed bark.

Grattan, D.W. and R.W. Clarke.  “Conservation of Waterlogged Wood.”  In, Conservation of Marine Archaeological Objects. Ed Colin Pearson.  Butterworth. London and Boston. 1987. 164-206   

Ellen Carrlee’s Notes: This is really the most comprehensive description of PEG use and especially its history, but of course it ends in 1987 AND this book is out of print and can be hard to come by.

  If PEG 3350 is too bulky to penetrate the cell wall, osmotic pressure could build and cause collapse.  Microcapillaries in the cell wall thought to be around 10nm in deteriorated wood. Idea that bulking the cell wall without bulking the lumina has better results: less PEG oozes out, more natural appearance.  Freeze drying gives a more even distribution of PEG.  Grades of PEG over 600 need to be warmed in order to be completely dissolved, and the complete solubility of PEG in water is very important.  Beginning impregnation with a low percentage of PEG is important to prevent osmotic collapse.  Up to 30% PEG 400 is needed to bulk the cell wall.  Freeze drying helps to keep it in there.  Very deteriorated wood doesn’t have much cell wall and so the low mw PEG can’t stay in there as well.  At the eutectic, PEG can’t freeze so you have a drying from with solid on one side and a mushy PEG solution on the other side. 

Grattan, David W.  “International Comparative Study; Report”  .  ICOM Committee For Conservation Working Group on Wet Organic Archaeological Materials Newsletter. no 14. Feb 1986. 

Ellen Carrlee’s Notes:  I don’t remember seeing this published as a final thing elsewhere?  Grattan described his work at CCI.  He treated some samples with equal parts PEG 400 and PEG 3350 raised in 10% increments up to 30% v/v.  Frozen at -40C and then freeze dried at -20C.  results were good, but the very deteriorated samples should have had less 400 more 3350.   Second batch placed in PEG 3350 in sequential batches of 10%, 20%, 30%m 40%, and 50% v/v and then freeze dried.  Grattan feels the PEG reach the eutectic and did not freeze, so unfrozen PEG exuded onto the surfaces during freeze drying and some surface collapse.

Grattan, David W.   “Some Observations on the Conservation of Waterlogged Wooden Shipwrecks.”  AICCM  Vol. 12 No 3 and 4. 1986.

Ellen Carrlee’s Notes: Diagram of meniscus for water in a capillary, discussion of capillary tension induced collapse.  Issue of PEG penetration into white oak timbers.  Air pockets might prevent penetration.  For more deteriorated wood, concentrations over 50% are better, and fill the lumens in addition to bulking the cell wall.  Less deteriorated wood does all right with 10-30% which only bulks the cell wall.  Capillary action during drying concentrates PEG at the surface and depletes the core…this can be overcome using concentration over 50%. (ellen: also, if you freeze, doesn’t ice crystal formation influence where the PEG ends up?)  For humidity about 80% all PEGs are affected.  Lower concentrations of PEG can be used with freeze drying than with air drying.

Grattan, David W.  “A Practical Comparative Study of Several Treatments for Waterlogged Wood”  Studies in Conservation Vol 27 No 3 Aug 1982 pp 124-136

Ellen Carrlee’s notes: Water content is a rough guide to the state of deterioration.  For smaller sample, no advantage to heating the PEG 400.  Didn’t help with penetration, shrinkage or cracking, but it did make end result darker.  In larger objects, heat may speed up the diffusion.  PEG 400 can end up soapy and attract dust.  Can melt some PEG 4000 on surface to make it stronger and less absorbent.  PEG 540 is a 50/50 blend of 300 and 1540 MW ave of 500-600…tends to creep out of the wood, looks heavy, dark, waxy.  Can be introduced unheated and unstirred in 10% increments over 18months.  Final concentration 64% v/v. 

Grattan, David.  “A Practical Comparative Study of Treatments for Waterlogged Wood part II The Effect of Humidity on Waterlogged Wood.”  Proceedings of the ICOM Waterlogged Wood Working Group Conference Ottawa 1981. pub 1982 pp. 243-252.

Ellen Carrlee’s notes: Wood treated with low MW PEG (400 or 540 blend) should not be exposed to RH above 60%.  Below that shouldn’t matter.  Union Carbide PEG 4000 has been renamed PEG 3350.

Hamilton, Donny L. Methods of Conserving Archaeological Material from Underwater Sites.  Nautical Archaeology Program Department of Anthropology Texas A&M University.  1998.

Ellen Carrlee’s notes: Amount of water in waterlogged wood is calculated: weight of wet wood minus weight of oven dried wood divided by weight of the oven dried wood and multiplied by 100 to give % water.  Anything over 200% is considered degraded.  Explanations of other treatments for waterlogged wood are also given.

Hoffmann, Per, Adya Singh, Yoon Soo Kim, Seung Gon Wi, Ik-Joo Kim, Uwe Schmitt.  “The Bremen Cog of 1380: An Electron Microscopic Study of it Degraded Wood Before and After Stabilization.”  In Holzforschung Vol 58 No 3 2004 pp 211-218

Ellen Carrlee’s notes: Two-step PEG treatment for wood degraded primarily by erosion bacteria.  SEM/TEM investigation.  In degraded tissues, all cell types were filled with PEG 3000.   Non-degraded tissues are impermeable to PEG 3000 and impregnated only with PEG 200.  Confirms that PEG 200 goes into the cell walls.

Hoffman, Per.  “On the Stabilization of Waterlogged Softwoods with Polyethylene Glycol (PEG).  Four species from China and Korea.”  Holzforschung. Vol. 44 No 2.  1990.  pp 87-93.

Ellen Carrlee’s notes: Best stabilization of degraded softwoods is 50% PEG 4000 with cross section shrinkage of only 2-4%. 

Hoffmann, Per.  “On the Stabilization of Waterlogged Oakwood with PEG II Designing a Two-Step Treatment for Multi-Quality Timbers.”  Studies in Conservation 31 (1986) pp.103-113

Ellen Carrlee’s notes: Bremen Cog PEG 200 and then PEG 3000.  Two step for thicker woods with outer layer of degraded wood and a core of less degraded wood like oak and pine.  Can even do simple air drying afterwards.  Results with intermediate MW not as good as two step.  PEG 200 stabilizes slightly degraded wood better than PEG 300.  Maybe some lower MW PEG diffuses out during the second step, but some is trapped or adsorbed in the capillaries.  Doesn’t weep until RH is 86%.  Can be air dried, too big for a freeze dryer.

Hoffmann, Per. “On the Stabilization of Waterlogged Oak with PEG – Molecular Size Versus Degree of Degradation.”  Waterlogged Wood Study and Conservation, Proceedings of the 2nd ICOM Waterlogged Wood Working Group Conference, Grenoble, France.  1984.  pp. 243-252.

Ellen Carrlee’s notes:  More degraded oak does better with PEG 3350, while less degraded does better with PEG 200.  PEG 1450 is poorer for both.  A 2-step method is more effective.  For a long time people were afraid to use anything under PEG 1500 for fear it would be too hygroscopic.

Jakes, K.A. and L.R. Sibley.  “Survival of Cellulosic Fibres in the Archaeological Context.” In Science and Archaeology. No. 25, pg 31-38. 1983.* Jeberien, Alexandra and Malcolm Bilz.  “Comparison of Air Dried and Freeze Dried Solutions of Polyethylene Glycol 3350”  In ICOM WOAM Newsletter No. 31 June 2000.

Ellen Carrlee’s notes: They expected all to line the walls and bottom of beakers.  Air dried samples had consistency of beeswax and occupied only the bottom the beaker, might have lined walls if they were more porous?  Freeze dried samples had a powdery matrix appearance and occupied the full volume that the frozen water/PEG mix had originally occupied.  For the freeze-dried, when they were returned to low temperature, higher concentrations that had been freeze-dried (20% and above) showed some concentrated PEG solution at the bottom of the beaker that had not been able to get past plugs of PEG.  5% did not have that, so water must have escaped.  

Jensen, Poul; Grethe Jorgensen, Ulrich Schnell.  “Dynamic LV-SEM Analyses of Freeze Drying Processes for Waterlogged Wood”  Proceedings of the 8th ICOM Group on Wet Organic Archaeological Materials Conference, Stockholm, 11-15 June 2001 Pub.  2002 pp.319-333

Ellen Carrlee’s Notes: Looking at distribution of PEG in wood with Low Vacuum Scanning Electron Microscopy (can avoid sputter-coating of SEM and the bias it introduces.)  Machine itself acts like a freeze-dryer with wet samples.  Phase diagrams for PEG done by different authors usually don’t agree, but they all agree the eutectic is around 55% (w/w) for all the mw of PEG.  Eutectic temperatures are not in agreement.  Below the eutectic temperature, a solid lamellar eutectic phase forms between the ice crystals.  Phase diagram they suggest for PEG 6000 shows solid PEG as well as a solid PEG/ice mixture at freezing temperatures with a concentration above 55% (eutectic.)  Below the eutectic, all PEG solutions result in 3-9% expansion at temps below freezing.  Ice has 9% expansion, PEG has 7% volumetric contraction.  Is this a primary function of the PEG?  PEG solutions below 55% all expand on solidifying.  PEG concentrated in the later wood and distributed irregularly in the early wood.  Collapse can be avoided if we stay below the eutectic temperature.  When ice forms, the PEG gets more concentrated.  Formation of large ice crystals contributes to uneven distribution of PEG.  Even distribution of PEG is only possible for eutectic concentrations.  PEG has a low affinity for the secondary cell wall (Jensen’s PhD thesis from 1995.)  Heating after freeze drying causes the PEG to aggregate on surfaces of cell wall and give better distribution.  They suggest investigating methods to nucleate smaller ice crystals and thus better distribution.

Kaenel, Gilbert.  “PEG Conservation of a Gallo-Roman Barge from Yverdon-les-Baines (Canton of  Vaud, Switzerland.)”  Proceedings of the Fifth ICOM Waterlogged Archaeological Materials Conference.  Portland, Maine 16-20 August 1993.  Pub 1994.  pp. 143-165.

Ellen Carrlee’s notes: Mostly oak, treated in a tank with PEG 4000 raised from 15% to 85% at 60C over 18months of impregnation.  AD 400.  Slow drying, natural looking finish reported.

Keene, Suzanne.  “Waterlogged Wood from the City of London.”  Proceedings of the ICOM Waterlogged Wood Working Group Conference Ottawa 1981. pub 1982 pp. 177-180

Ellen Carrlee’s notes: Variety of different hardwoods and softwoods.  PEG 4000 was used up to 90% at 50-60C, but wood came out dry and splintery so they switched to PEG 1500.  Rinsed with hot water, wrapped in towels and dried slowly in the dark.  Objects come out heavy, brittle, but not much shrinkage.  A little darker, and fine detail is preserved.  For freeze drying, PEG 400 left the wood too fragile, 40-50% PEG 1500 or 4000 worked better.  She’s down on acetone/rosin because while other colleagues have had luck with metal handled tools, she’s not had the best luck and working with hot acetone is difficult.

Lindblad, Cecilia and Ingmar Persson. “Polyethylene Glycol/ Polyethylene Oxide: An Overview of the Physical-Chemical properties of PEG/PEO”  Presented at the ICOM-CC Working Group on Wet Organic Archaeological Materials in Amsterdam, 2007.  Not yet published.

Ellen Carrlee’s notes:  Persson generously sent me a copy.  Describes a lot of chemistry of the polymer.  There’s no clear distinction between PEG/PEO.  PEG extremely soluble in water, but solubility of PEO actually decreases with high temps, salt, and strong stirring.  Exponential increase in viscosity with higher molecular weight.  Bonding discussed.  Hydration radius for PEG 4000 at 30C is 50 nm.  High mw PEGs  above PEG 1000 form random coils and low mw PEGS below PEG 600 maybe form stretched aggregate chains?  PEG on objects treated with high temps show signs of decomposition. 

Masuzawa, Fumitake and Yoichi Nishiyama.  “Experiments on the Impregnation of Waterlogged Wood with PEG Part II”  Conservation Science Bulletin.  Hozon Kagaku Kentyushitsu Kiyo.  Vol. 3 1974 pp39-46

Ellen Carrlee’s notes: this is from a literature review in ICOM-CC WOAM Newsletter No 8 Nov 1982.  Size greatly affects time for saturation: 50-60 days for 3cm wood, but more than 120 days for oak of 7.5cm

Masuzawa, Fumitake.  “Change of Waterlogged Wood Impregnated with PEG Along the Lapse of Time.”  Conservation Science Bulletin.  Hozon Kagaku Kentyushitsu Kiyo.  Vol. 3 1974 pp. 52-58

Ellen Carrlee’s notes: this is from a literature review in ICOM-CC WOAM Newsletter No 8 Nov 1982.    Reviewing wood treated with PEG after one year.  Wood treated with PEG 540 blend absorbed moisture, oozed out and there was shrinkage.  PEG 2000 showed radial cracks after 3 months and some expansion.  PEG 3300 showed no great change.  Based on other articles, they were probably looking at oak.

Murray, Howard.  “The Conservation of Artifacts from the Mary Rose.” Proceedings of the ICOM Waterlogged Wood Working Group Conference Ottawa 1981. pub 1982 pp. 12-19

Ellen Carrlee’s notes: Wood treated was poplar, oak, ash and softwoods.  Passive holding included spraying with boric acid and double wrapping in sealed polyethylene sheeting (dried out somewhat and got cracking and salt efflorescence within 6 months) or submersion in water (resulting in additional expansion and softening.)  Pre-treatment with 5% EDTA as well as ultrasonic cleaning to remove salts and iron corrosion products, although more than 48 hours in EDTA resulted in notable softening.  PEG 3400 up to 50%.  Mostly doing freeze drying, although getting good results with drying only the surface in the freeze drier and then allowing it to air dry.  Excess PEG removed with hot air, IR lamps, and ethanol swabs.  Reconstruction done with wooden dowels, nitrocellulose adhesive and melted PEG 6000 at 50% as a surface coating.

Rodgers, Bradley.  ECU Conservator’s Cookbook: A Methodological Approach to the Conservation of Water Soaked Artifacts.   Chapter 2: Waterlogged Wood.  Herbert P. Paschal Memorial Fund Publication.  East Carolina University.  1992. 

Ellen Carrlee’s notes: ECU= East Carolina University.  Dr Bradley Rodgers teaches conservation of material from underwater environments. Don’t put items from saltwater directly into fresh water, needs to be gradual or the salt water moves out faster than freshwater can move in, causing collapse (ie pruny fingertips in the bath.)  Specific gravity of several woods are given.  Pits in cell walls have valves, and if these are blocked it is harder to impregnate the wood.  Hard to see w/o SEM.  PEG solution is heated, and you weigh it weekly after you achieve 50% PEG.  Should stabilize at about 20% weight gain.  Might go up to 35%.  If you’re using PEG 3350, maybe even 45%  Wood in good condition sometimes as little as 15%.  Sucrose treatment described.  Brush coating of 50% PEG 3350 to consolidate the outer layer.  Ellen’s note: Bradley’s treatments don’t always match up to AIC standards and ethics, and there was a big dustup over one of his recent publications, an update and expansion of the material in this book.

Singley, Katherine.  The Conservation of Archaeological Artifacts from Freshwater Environments  Lake Michigan Maritime Museum, South Haven, Michigan 1988. 

Ellen Carrlee’s notes: She tends to use PEG 300 and 400 with 4500 applied later hot.  Recommends pretreating wood contaminated with iron salts with 3% perchloric acid, soaked for about a week.  This dissolves iron and opens up the pore structure to increase the penetration of PEG.  PEG 300 at room temp 10% for six months, then removed and wrapped in plastic with regular surface brushing of higher concentrations 3X a week increasing the concentration every two months until 80% reached.  Slow drying at high RH was used.  50% PEG 4500 paste was then applied with hot air.  This layer was thought to prevent oozing out of lower MW PEG.  She also uses 10% PEG 300, soaked for a year and then freeze dried. 

Viduka, Andrew.  Survey of Methods Used by Some Large institutions Specializing in the Conservation of Wet Organic Archaeological Materials.  Report as the 2002 Churchill Fellow: Winston Churchill Memorial Trust of Australia.  2002. 

http://www.churchilltrust.com.au/res/File/Fellow_Reports/Viduka%20Andrew%2020021.pdf.

Ellen Carrlee’s Notes: Viduka visited several labs and wrote up his observations.  Texas CRL sees, among other things, darkening of surfaces with high PEG concentrations as a disadvantage.  Parks Canada was looking at whether PEG modifies the crystal size of water.  Tara Grant at CCI has generally found air-drying to be unsuccessful.  Wooden material from Nydam Mose, 5th C Iron Age site treated in Denmark, is highly deteriorated with only lignin remaining.  NMD is looking into sucrose, wood flexibility post-treatment, Cellusolve method, lots of vacuum freeze drying, review of old treatments, deacidification of low mw PEG timbers, experimental cold air drying.  On the Vasa, acid affected areas have white or yellow build-up and generally appear on areas treated with PEG 400 and not PEG 4000.  Remedial treatment is a spray with sodium bicarbonate and soda with a pH >10 and covered with plastic wrap.  Skuldelev ships were some of the earliest to be conserved with PEG 4000, and 40 years later, they still have a mw of 3900.  Using too high a mw on only slightly degraded wood is a problem.  Too much PEG would give a purple or blue sheen on the surface.  Longer immersion made bigger timbers darker than smaller pieces.  Heating for re-shaping caused darkening of the surface. Glenn McConnachie’s PhD reveals that even well-preserved waterlogged oak from the Mary Rose has 30% volumetric shrinkage after air drying. 

Vynckier, Jozef.  “Examination and Conservation of Basketwork from a Roman Well at Destelbergen”  Bulletin de’Institut Royal du Patrimoine Artistique Vol 8.  1965  (Flemish?) 

Ellen Carrlee’s notes: Linden bark basketry fragments immersed 4 months in carbowax 4000

Watson, Jacqui. “The Application of Freeze-Drying on British Hardwoods from Archaeological Excavations.”  . Proceedings of the ICOM Waterlogged Wood Working Group Conference Ottawa 1981. pub 1982

Ellen Carrlee’s notes: Fungal degradation in the cell wall contributes to splintering when freeze-dried.  Mineral deposition or replacement in outer layers is common in archaeological wood, especially with iron.  Sometimes these can be seen as casts of material that is now lost.  Chelating agents etc remove the iron.  But iron also interacts badly with PEG.  Early warning in this article of problems with iron salts and PEG. Even if the soil has low iron content, there is sometimes high iron content in the wood. Oak freeze dried after 10% PEG 400 for 4-6 weeks had deep cracks next to the rays, and some distortion and collapse in some small fibers.  Using 10% PEG 400 and 15% PEG 4000 resulted in less cross checking on the surface.  Wood that underwent freeze-drying without impregnation collapsed, and showed crystals (calcium and sulphur) that precipitated out that did not do so when PEG was used.  Pitting details in the vessels that are useful for ID were obscured after treatment with PEG 4000.  Mixed PEG solutions work best when using freeze-drying.

Young, Gregory S.  “Microscopy and Archaeological Waterlogged Wood Conservation.”  CCI Newsletter, No. 6, September 1990.  pp 9-11.

Ellen Carrlee’s notes: General overview of PEG treatment/ research.  Deterioration greatly improves the ability of PEG to penetrate and treat wood successfully, but most excavated waterlogged wood is only moderately deteriorated.  White oak, various cedars, and white ash are hard to penetrate, while aspen, cottonwood, alder and spruce allow greater penetration.  Caution with determining degree of deterioration from thin 3mm cross sectioned wafers of wood examined under the microscope, as the sample has a lot of disrupted wood cells and suggests more cell wall accessibility than there really is. 

Young, Gregory S. and Richie Sims. “Microscopical Determination of PEG in Treated Wood – the Effect of Distribution on Dimensional Stabilization.”  Conservation of Wood and metal: Proceedings of the ICOM Conservation Working Group on Wet Organic Archaeological Material and Metals.  Freemantle, Western Australia Museum. 1987  Pub 1989. pp109-140

Ellen Carrlee’s Notes:  Fluorescence microscopy.  25-35% PEG 200 and 3350.  Found less penetration with larger molecular weights.  Dimensional stabilization correlates with full impregnation of secondary cell wall.  Eight different species tested showed broad range of access to cell wall. 

Young, Gregory S. and Ian N.M. Wainwright.  “Polyethylene Glycol Treatments for Waterlogged Wood at the Cell Level.”  Proceedings of the ICOM Waterlogged Wood Working Group Conference Ottawa 1981.  pub 1982 pp.107-116

Ellen Carrlee’s notes: Shrinkage happens when hygroscopically bound water within the cell walls is lost when wood is below the fiber saturation point (FSP.)  Lower MW PEG is expected to stay in the cell wall, while higher MW PEG bulks the lumina.  Cobalt thiocyanate is a microscopical stain when dissolved in non-aqueous histological grade cedarwood oil.  The oil (cedrene and cedrol) is immiscible with both water and PEG.  It  dissolves the cobalt thiocyanate, but readily gives it up to the PEG in wood sections. 

PEG 400 (35%) in cell wall capillary matrix

PEG 3350 (60%) bulked cell lumina

PEG 540 blend (64%) in both cell wall and lumina  540=1450 + 300 together equal MW mixture

Over 3000 shouldn’t get into cell wall, above 2000, should be impeded somewhat.  MW below 400 penetrate better.  PEG must penetrate the cell wall for best dimensional stability.  Double bulking is good, though.


What Do We Know About PEG?

April 8, 2009

 

WHAT DO WE KNOW ABOUT PEG?
Notes in preparation of basketry treatments at the Alaska State Museum
Ellen Carrlee, Conservator
April 8, 2009
        

THE MOLECULE
* Polyethylene glycol is a non-ionic polyhydroxyl compound.  Different molecular weights
have different solubility, surface tension, viscosity, freezing point,
and melting points.  PEG tends not to interact with biological chemicals.
(Rey et al 2004)   

* PEGs are polyether-diols with two terminal hydroxyl groups and many
alternating ether linkages.  PEG 200 has a lot of diol character and is
more soluble in water, while PEG 4000 has more polyether character and
the solubility is due more to hydrogen bonding.  (Brownstein 1982)

* There’s no clear distinction between PEG/PEO.  PEO is polyethylene oxide. (Lindblad and  Persson
2007) 

* Soluble in water because of hydrogen bonding of water molecules to
electron-rich oxygen atoms in the polymer chain. (Brownstein 1982)

* Exponential increase in viscosity with higher molecular weight.
(Lindblad and  Persson 2007)  

* Acts like a surfactant to reduce the surface tension of water and
therefore the PEG reduces damage from capillary tension when water
evaporates.  The magnitude of the decrease in surface tension correlates
directly to the molecular weight of the PEG.  (Rey et al 2004)  

* Could use of surfactants lower interfacial tension forces and speed
penetration?  Most non-ionic surfactants work at concentrations of ,1%,
and have a structure similar to PEG except it has a hydrocarbon group on
one end.  (Brownstein 1982)  

* PEG readily forms complexes with many materials and does not behave in
wood the same way it does alone.  (Brownstein discussion 1982)

* PEG extremely soluble in water, but solubility of PEO actually
decreases with high temps?  (Lindblad and  Persson 2007)

* Grades of PEG over 600 need to be warmed in order to be completely
dissolved, and the complete solubility of PEG in water is very
important.  (Grattan and Clarke 1987)

* Urea and PEG can bond together to make very strong complexes.  PEG and
phenols also bond.  Interestingly, lignin is a polyphenol. (Brownstein
1982)

* Microcapillaries in the cell wall
thought to be around 10 nm in deteriorated wood. (Grattan and Clarke 1987)

* Cell wall has capillaries from 10-80 nm, and pores in pit membranes up
to 150 nm.  Water molecule is 0.2 nm, and various PEGs: PEG 400 is about
2 nm, PEG 1000 is about 4.5 nm and PEG 4000 is about 18 nm.  (Hoffmann,
1982.)

* Hydration radii of PEG 4000 could be around 50 nm (Lindblad and Persson
2007)

* High mw PEGs  above PEG 1000 form random coils and low mw PEGS below
PEG 600 maybe form stretched aggregate chains?  (Lindblad and Persson
2007)

* Size of the PEG molecule is hard to determine because it can coil, fold, twist etc.
(Brownstein 1982)

* PEG does not degrade much with changes in pH although it happens a bit
more if heated.  (Brownstein 1982)

* Thermal aging increases PEG degredation (Bilz et al 1994)

* For PEG use in chromatography, it is important that PEG not degrade
and they use temps up to 250C, but oxygen is also eliminated.  In the
presence of oxygen, PEG decomposition from heating is usually seen in
darkening, less viscosity, and lower pH.  PEG degradation occurs by
random chain scission.  (Brownstein 1982)

* PEG ages more slowly in wood than by itself .  Lignin may act as an anti-oxidant. (Grattan 2000)

* PEG is chemically unlikely to crosslink with the constituents of the wood. (Grattan 2000)

* Determining where the PEG goes in the cell structure is usually done
with cobalt thiocyanate staining.  The stain inhibits autofluoresence of
lignin (PEG does not affect fluorescence) and the stain only bonds with
PEG, so if the fluorescence is quenched it shows where the PEG has gone.
(Young and Wainwright 1982)

PERCENTAGES AND MWs
* Beginning impregnation with a low percentage of PEG is important to
prevent osmotic collapse.  (Grattan and Clarke 1987)

* Up to 25% PEG 400 needed to control shrinkage (Grattan discussion
1982)

* Up to 30% PEG 400 is needed
to bulk the cell wall.  Freeze drying helps to keep it in there.  Very
deteriorated wood doesn’t have much cell wall and so the low mw PEG
can’t stay in there as well. (Grattan and Clarke 1987)

* PEG 400 at 10-15% is not expected to result in appreciable bulking of
cell lumina .  (Young and Wainwright 1982)

* For smaller samples, there is no advantage to heating the PEG 400, it does not help with penetration, shrinkage or cracking…but it did make the end result darker.  In larger objects, heat may speed up the diffusion.  PEG 400 can end up soapy and attract dust. (Grattan 1982)

* Results from using an intermediate mw PEG are not as good as using a two-step method with a low mw first, and then a high mw. (Hoffmann 1986)

* More degraded oak does better with PEG 3350, while less degraded does
better with PEG 200.  PEG 1450 is poorer for both.  A 2-step method is
more effective. (Hoffmann, 1984)

* Two-step PEG treatment good for wood degraded primarily by erosion
bacteria.  In degraded tissues, all cell types were filled with PEG
3000.   Non-degraded tissues are impermeable to PEG 3000 and impregnated
only with PEG 200.  SEM/TEM investigation confirms that PEG 200 goes
into the cell walls. (Hoffmann 2004)

* Two-step is better method for wood that includes both sound and deteriorated areas (Johns 1998)

* Wood with fairly intact cell wall structure may suffer from shrinkage after treatment with high molecular weight PEG alone.  Could the hygroscopic PEG itself pull water out of the smaller structures where it cannot penetrate?  (Astrup 1993)

* Low mw PEG in cell lumina and larger voids in cell wall will diffuse
back out of the wood again, only remains in the capillary system.
Larger mw needed for those larger voids (Hoffmann 1986.)

* Lower mw PEG penetrates the micro-capillaries of the cell wall, while
higher mw penetrates the lumens, flows through the vascular system
(Grattan 1986.)

* Lower mw PEGs 200-600 replace some of the bound water in the cell
walls.  Higher mw PEGs 1000-3000 are expected to bulk the cell lumina,
but they are too large to get into the cell walls. (Young and Wainwright
1982)

* PEG 300 has access to middle lamella, but PEG 400 does not (Young and
Wainwright 1982)

* In sound Populus sp (aspen, cottonwood)  PEG 200, 400 and 600
penetrate the capillary network of the secondary cell wall. (Grattan
1986, Young 1982)

* PEG 1450 is still expected to penetrate the cell wall (Young and
Wainwright 1982)

* PEG has a low affinity for the secondary cell wall (Jensen’s PhD
thesis from 1995, mentioned in Jensen et al 2002)

* Tests with oak and SEM/TEm examination, all cell types filled with PEG 3000 in degraded wood, while non-degraded tissues were impermeable to PEG 3000 and only impregnated with PEG 200.  (Hoffmann et al 2004)

* For 25-35% PEG 200 and 3350:  Fluorescence microscopy  found less
penetration with larger molecular weights.  Dimensional stabilization
correlates with full impregnation of secondary cell wall.  Eight
different species tested showed broad range of access to cell wall.
(Young and Sims 1987)

* Idea that bulking the cell wall without bulking the lumina has better
results: less PEG oozes out, more natural appearance.  (Grattan and
Clarke 1987)

* PEG 200 stabilizes slightly degraded wood better than PEG 300 (Hoffmann 1986)

* PEG 200 goes into the cell walls (Hoffmann et al 2004)

* PEG 200 above 20% needed to penetrate secondary cell walls of red
cedar bark, but to avoid moist surface it needs to be below 50%.
Penetration happens very quickly.  20% PEG 200 seemed to penetrate fresh cedar bark the same at 4 months as it did at 12 months of soaking. (Bilz et al 1998)

* PEG solutions below 55% all expand on solidifying.  The only way to have even distribution of PEG with freeze drying is to hit the eutectic. (Jensen at al 2000)

* For both highly degraded and less degraded wood, waterlogged softwoods treated successfully with 50-55% PEG 4000. (Astrup 1993)

*  Grades of PEG over 600 need to be warmed in order
to be completely dissolved, and the complete solubility of PEG in water
is very important.   ( Grattan and Clarke 1987)

* PEG 3350 is too bulky to penetrate the cell wall, osmotic pressure
could build and cause collapse.  (Grattan and Clarke 1987)

* Too much PEG 3350 results in heavy wood that is harder to dry. (Cook and Grattan 1990)

* For very deteriorated wood without the availability of freeze drying,
concentrations over 50% is usually used so the core is not depleted as
the capillary action during drying leaves the PEG at the surface, where
it can seem oozy and hygroscopic.  Freeze drying allows for more even
distribution of the PEG inside the wood and allows for a lower
concentration to be used (15-25%)  (Grattan, 1986)

* Size greatly affects time for saturation: 50-60 days for 3cm wood, but
more than 120 days for oak of 7.5cm (Masuzawa and Nishiyama 1973)

* Amount of water in waterlogged wood is
calculated: weight of wet wood minus weight of oven dried wood divided
by weight of the oven dried wood and multiplied by 100 to give % water.
Anything over 200% is considered degraded (Hamilton 1998)

* After reaching 50% PEG, weighing the object weekly will tell when it is done.  Should stabilize around 20% weight gain.  Might go up to 35%   With PEG 3350, maybe even 45%.  Wood in good condition may gain as little as 15%.  (Rodgers, 1992)

* Wood treated with low mw PEG (400 or 540 Blend) should not be exposed to RH above 60%.  Below that RH it shouldn’t matter. (Grattan 1982)

* If you put object in successive pure grades of PEG, the lower grades
will leach out.  You must add the higher mw to a solution already
containing the lower one.  (Howard Murray discussions 1982)

MANUFACTURE
* The correct chemical nomenclature in Chemical Abstracts is polyoxy.
1-2 ethanediyl  Appendix III. In book. Proceedings of the ICOM
Waterlogged Wood Working Group conference: Ottawa, 15-18 September 1981.
ICOM Waterlogged Wood Working Group (1982) pp 292

* Union Carbide makes Carbowax.  Other trade names have included Polywachs
and Modopeg.

* PEG 1500 changed to PEG 540 and 1540 became 1500. (Grosso 1976)

* A 1977 article says that “PEG 1500 was recently redesignated PEG 540”
(McCawley, 1977)

* PEG 540 is an equal mixture by weight of 1450 and 300.  (Young and
Wainwright 1982)

* Sometime around 1981, the following changes were made:
Carbowas 1540 became 1450
Carbowax 4000 became 3350
Carbowax 6000 became 8000
(Appendix III. In book. Proceedings of the ICOM Waterlogged Wood Working
Group conference: Ottawa, 15-18 September 1981.  ICOM Waterlogged Wood
Working Group (1982) pp 292

* Carbowax 1450 has molecular weights ranging from 1300-1500 (Singley
1982)

* PEG 540 blend, PEG 1450, PEG 3350 and PEG 4600 were in active use in the
mid-1980’s.  (listed in table 9.1 page 169 Grattan and Clarke 1987)

* “What was once called PEG 1500 is now called 540 Blend…PEG 1540 is now
called PEG 1500 and PEG 4000 is now called PEG 3250”  (Hamilton 1998)

FREEZER OR FREEZE DRYER
* A cryoprotectant is a substance used to protect biological tissue from
freezing damage due to ice formation.  Ice expands 8% in volume from its
liquid state.  As a cryoprotectant, PEG counteracts this.  Some
cryoprotectants form hydrogen bonds with wood as water molecules are
displaced. (Rey et al 2004)

* PEG can’t act as a cryprotectant on its own?  Does it need glycerol?
Cryprotectants often work better as a mixture of more than one. PEG is
much better as a cryoprotectant than sugar.   PEG is used as a
cryoprotectant for doing XRD. (Rey et al 2004)

* Wood that underwent freeze-drying without impregnation collapsed, and
showed crystals (calcium and sulphur) that precipitated out that did not
do so when PEG was used.  Pitting details in the vessels that are useful
for ID were obscured after treatment with PEG 4000.  Mixed PEG solutions
work best when using freeze-drying. Ellen: could this be because
combinations of cryoprotectants work better than just one?
(Watson 1982)

* Freeze drying gives a more even distribution of PEG than air drying.  (Grattan and
Clarke 1987)

* Capillary action during drying concentrates the PEG at the surface of the artifact and depletes the core.  This can be overcome using a concentration of over 50%.  Lower concentrations of PEG can be used with freeze drying than with air drying. (Grattan 1986)

* Comparison of Air Dried and Freeze Dried Solutions of Polyethylene
Glycol 3350: They expected all to line the walls and bottom of beakers.
Air dried samples had consistency of beeswax and occupied only the
bottom the beaker, might have lined walls if they were more porous?
Freeze dried samples had a powdery matrix appearance and occupied the
full volume that the frozen water/PEG mix had originally occupied.  For
the freeze-dried, when they were returned to low temperature, higher
concentrations that had been freeze-dried (20% and above) showed some
concentrated PEG solution at the bottom of the beaker that had not been
able to get past plugs of PEG.  5% did not have that, so water must have
escaped.   (Jeberien and Bilz 2000)

* Fungal degradation in the cell wall contributes to splintering when
freeze-dried (Watson 1982)

* At the eutectic, PEG can’t freeze so you
have a drying from with solid on one side and a mushy PEG solution on
the other side. (Grattan and Clarke 1987)

* Low Vacuum Scanning Electron microscope acts like a freeze-dryer with
wet samples.  Phase diagrams for PEG done by different authors usually
don’t agree, but they all agree the eutectic is around 55% (w/w) for all
the mw of PEG.  Eutectic temperatures are not in agreement.  Below the
eutectic temperature, a solid lamellar eutectic phase forms between the
ice crystals.  Phase diagram they suggest for PEG 6000 shows solid PEG
as well as a solid PEG/ice mixture at freezing temperatures with a
concentration above 55% (eutectic.)  Below the eutectic, all PEG
solutions result in 3-9% expansion at temps below freezing.  Ice has 9%
expansion, PEG has 7% volumetric contraction.  PEG solutions below 55%
all expand on solidifying.  PEG concentrated in the later wood and
distributed irregularly in the early wood.  Collapse can be avoided if
we stay below the eutectic temperature.  When ice forms, the PEG gets
more concentrated.  Formation of large ice crystals contributes to
uneven distribution of PEG.  Even distribution of PEG is only possible
for eutectic concentrations.  Heating after freeze drying causes the PEG
to aggregate on surfaces of cell wall and give better distribution.
They suggest investigating methods to nucleate smaller ice crystals and
thus better distribution. Only one-step tested, not two step method. (Jensen et al 2002)

* Heating after freeze drying causes PEG to aggregate on the surfaces of cell walls and give better distribution.

* Murray has reported good results with only drying the surface in the freeze dryer and then allowing it to air dry (Murray 1982.)

* Ice recedes 1-2cm below the surface in Grattan’s natural freeze-drying
method Ellen: For us that would be the full size of the basketry
artifact?!
(Grattan discussion in Ottawa 1982)

* Does PEG modify the crystal size of water? (Viduka, 2002)

* Description of treatment of two leather boots followed by freezing then “freeze drying” in non vacuum freeze drier.  Objects placed in polypropylene container with silica gel inside a chest freezer. (Storch 1997)

AFTER TREATMENT 

* Excess PEG can be removed with hot air, IR lamps, and ethanol swabs (Murray 1982)

* Can swab with ethanol to remove excess after treatment (Masuzawa and
Takatougin 1973)

* PEG-Wood combo has some hydrogen bonding that makes it less
hygroscopic than pure PEG. Below 60% weeping should not occur (David
Grattan discussion in Ottawa 1981)

* If excess PEG is not
used and the RH is kept below 60% treated artifacts do fine(Grattan 2000)

* PEG 400 in 25-35% v/v impregnation solutions should not show not much
change with RH fluctuation, but in concentations less than 15% shows
some movement.  (Grattan 1982)* Above 80% concentration, PEG 4000 will ooze out of the wood (Grattan
1982)

* Reviewing wood treated with PEG after one year.  Wood treated with PEG
540 blend absorbed moisture, oozed out and there was shrinkage.  PEG
2000 showed radial cracks after 3 months and some expansion.  PEG 3300
showed no great change.  Based on other articles, they were probably
looking at oak. (Masuzawa 1974)

* PEG darkens considerably if heated over long periods, and presence of
oxygen seems to enhance the darkening. (Brownstein, discussion 1982)

* Heating for re-shaping caused darkening of the surface.  (Viduka 2002)

* When we preserve with PEG we are not capturing the “normal use size” because artifacts from waterlogged sites are in a swollen condition, perhaps 5-10% larger than they were in use. (Hoyle 1976)

* UV degrades lignin (Brownstein 1982)

Ellen: several articles also mention applying molten PEG of high mw to the surface after treatment to give more stability and resistance to RH.

PROBLEMS WITH PEG
* If PEG 3350 is too bulky to penetrate the cell wall, osmotic pressure
could build and cause collapse.  (Grattan and Clarke 1987)

* Excess PEG 540 blend left the surfaces on Ozette pieces was
hygroscopic and dark (Cooke and Cooke  1994)

* PEG corrodes iron  (MacLeod, I. D., Kenna C., 1990.)

* PEG corrodes all metals but especially iron (Hamilton 1998)

* Metal ions don’t interact well with PEG.  (Watson 1982)

* Iron compounds will depolymerize PEG at high temperatures (Hoffmann
1982)

* Seems that iron salts degrade higher molecular weight PEG (3350) a
bit, but not as notable for lower mw like PEG 400. (Bilz et al 1993)

* Mineral deposition or replacement in outer layers is common in
archaeological wood, especially with iron.  Sometimes these can be seen
as casts of material that is now lost.  Chelating agents etc remove the
iron.  But iron also interacts badly with PEG.  Early warning in this
article of problems with iron salts and PEG. Even if the soil has low
iron content, there is sometimes high iron content in the wood.  (Watson
1982)

* Vasa and other shipwreck timbers treated with PEG show sulfur-acid
breakouts in areas treated with PEG 400 only and not in areas with combo
of PEG 400 and 4000.  It shows as yellow or white colored build-up.
(Viduka 2002)

* Unstable sulphides in wood can oxidize to sulphates and eventually sulfuric acid,
leading to destruction of the wood.  (Grattan 2000)

* Formic acid formation in treated wood may be partly related to PEG (Glastrup et al 2006)

* Acetic acid formation in treated wood probably comes from the wood, and is age dependent. (Glastrup et al 2006)

* Pre-treatment with 5% EDTA as well as ultrasonic cleaning to remove slats and iron corosion products.  Longer than 48 hours in the EDTA results in notable softening.  (Murray 1982)

* If PEG reaches the eutectic and it does not freeze, unfrozen PEG
exudes onto the surfaces during freeze drying and there is some surface
collapse.  (Grattan Newsletter 1986)

* pH decreases with artificial aging and the decrease is greater for
higher temperatures, this might be indicating formation of acidic
degradation products. Excluding air (oxyen) slows the formation of
acids. Higher concentrations of PEG have less dissolved oxygen.
However, because it is a mixed solvent system, 4 might be neutral and
not acidic since pH refers to a water system? (Bilz et al 1993)

* In general, the molecular weight (measured as intrinsic viscosity)
decreased as PEG was artificially aged and more so with heat.  (Bilz et
al 1993)

* Heating during PEG impregnation causes darkening of the surface
(Grattan 1986)

* PEG on objects treated with high temps show signs of decomposition.
(Lindblad and Persson (2007)

* For PEG use in chromatography, it is important that PEG not degrade
and they use temps up to 250C, but oxygen is also eliminated.  In the
presence of oxygen, PEG decomposition from heating is usually seen in
darkening, less viscosity, and lower pH.  PEG degradation occurs by
random chain scission.  (Brownstein 1982)

* Less degradation if you take away oxygen.  A lot of good anti-oxidants
are not soluble in water.  Propyl gallate as an anti-oxidant does not
reduce PEG degradation and can form colored complexes with iron.
Butylated hydroxyl anisole (BHA) seemed to reduce degradation in both,
as long as the temperature was below 85C Concentrations have to be low
because it is not very soluble in water.  (Bilz et al 1993)

* BHA isn’t soluble enough to protect PEG from oxygen.  BHA is a harmful substance, even though it is used in the food industry.  Research into the addition of BHA to PEG solutions “highlights the fact the the solubility of PEG itself in water is quite tenuous.”   (Bilz and Grattan 1997)

* PEG did not seem to decrease in molecular weight in stored solutions
or in the artifacts over 10 years.  But perhaps the smaller molecules
were getting absorbed by the wood or otherwise not available to be
detected? (Bilz et al 1994)

* PEG ages more slowly in wood than
by itself.  Lignin may act as anti-oxidant.  PEG is chemically unlikely
to cross link with the constituents of the wood. (Grattan 2000)

* Lower concentrations of PEG 400 (below 40%) oxidize more than higher concentrations.

* Skuldelev ships treated with PEG 4000.  Forthy years later, mw was
measured at 3900 indicating the polymer chain had not significantly
degraded in that time. (Viduka 2002)

* Objects treated with PEG that were originally bent could un-bend if
not restrained during drying  (Cooke and Cooke  1994)

* PEG over 70% can draw water out of a well-preserved heartwood without
replacing it with PEG causing the wood to collapse.  (forgot ref, sorry)

Ellen: Treatment times are lengthy and take up space.  With a lot of
archaeological material, that means a lot of money.  Most treatments are
many months, some are many years.

 

REFERENCES

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Bilz, Malcolm, Tara Grant and Gregory S. Young.  “Treating Waterlogged
Basketry: A Study of Polyethylene Glycol Penetration Into the Inner Bark
of Western Red Cedar.”  Proceedings of the 7th ICOM-CC Working Group on
Wet Organic Archaeological Materials Grenoble 1998
.  pp.249-253

Bilz, Malcolm and David W. Grattan. “Strange Brew: BHA, PEG and H2O”  Proceedings of the 6th ICOM Group on Wet Organic Archaeological Materials.  Conference, York, 1996.  Pub 1997.  pp 385-398.

Bilz, Malcolm, Lesley Dean, David W. Grattan, J. Clifford McCawley, and
Leslie McMillen.  “A Study of the Thermal Breakdown of Polyethylene
Glycol.”  Proceedings of the Fifth ICOM Group on Wet Organic
Archaeological Materials conference, Portland, Maine, 16-20 August 199
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Blanchette, Robert A.; Hoffmann, Per “Degradation Processes in
Waterlogged Archaeological Wood”  Proceedings of the Fifth ICOM Group on
Wet Organic Archaeological Materials conference, Portland, Maine, 16-20
August 1993
pub. 1994

Brownstein, Allen “The Chemistry of Polyethylene Glycol.”  In book.
Proceedings of the ICOM Waterlogged Wood Working Group conference:
Ottawa, 15-18 September 1981
. Pub. 1982 pp 279-287.

Christensen, B. “The Conservation of Waterlogged Wood in the National
Museum of Denmark.”  Museums Tenniske Studier 1, National Museum of
Copenhagen, Denmark.  1970.

Christensen, M., M. Frosch, P. Jensen, U. Schnell, Y. Shashoua, O.F.
Nielsen.  “Waterlogged Archaeological Wood – Chemical Changes by
Conservation and Degradation.”  Journal of Raman Spectroscopy.  Special
Issue Raman Spectroscopy in Art and Archaeology II.  Vol. 37 Issue 10.
2006. pp.1171-1178.

Cook, Clifford and David Grattan.  “A Method of Calculating the
Concentration of PEG for waterlogged Wood.”  Proceedings of the 4th ICOM
Group on Wet Organic Archaeological Materials
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Cooke, Vincent, Deborah Cooke, and David W. Grattan.  “Reversing Old PEG
Treatments of Objects from the Ozette Site.”  Proceedings from the 5th
ICOM Group on Wet Organic Archaeological Materials Conference, Portland,
Maine 16-20 August. 1993
. 1994. pg 92-109

Florian, Mary-Lou E., Dale Paul Kronkright, Ruth E. Norton.  The
Conservation of Artifacts Made from Plant Materials
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Trust.  1990.

Florian, Mary-Lou.  “Anomalous Wood Structure: A Reason for Failure of
PEG in Freezer-Drying Treatments of Some Waterlogged Wood from the
Ozette Site.”  In book. Proceedings of the ICOM Waterlogged Wood Working
Group conference: Ottawa, 15-18 September 1981
.  pub 1982 pp85-98

Grant, Tara and Malcolm Bilz.  “Conservation of Waterlogged Cedar
Basketry and Cordage.”  Proceedings of the 6th ICOM Group on Wet Organic
Archaeological Materials York, 1996
. Pub 1997

Grattan, David W.  “International Comparative Study; Report”  ICOM
Committee For Conservation Working Group on Wet Organic Archaeological
Materials.  Newsletter
. No 14. Feb 1986.

Grattan, David.  Cons Dist List posting 30 Aug 2000

Grattan, D.W. and R.W. Clarke.  “Conservation of Waterlogged Wood.”  In,
Conservation of Marine Archaeological Objects. Ed Colin Pearson.
Butterworth. London and Boston. 1987. 164-206

Grattan, D. “Some Observations on the Conservation of Waterlogged Wooden
Shipwrecks.”  AICCM Bulletin, Vol. 12 No 3 and 4 1986.

Hamilton, Donny L. Methods of Conserving Archaeological Material from
Underwater Sites
.  Nautical Archaeology Program Department of
Anthropology Texas A&M University.  1998.

Grattan, David W.  “International Comparative Study; Report”  ICOM
Committee For Conservation Working Group on Wet Organic Archaeological
Materials.  Newsletter
. no 14. Feb 1986.

Grosso, Gerald. “Volume Processing of Waterlogged Wood at a Remote Archaeological Site: Modification of old Techniques, Identification of Special Problems and Hopes for Their Solution”.   In Pacific Northwest Wet Site Wood Conservation Conference, September 19-22. 1976 volume 1  Neah Bay. WA.

Hoadley, R. Bruce. Identifying Wood.  Accurate Results with Simple
Tools
.  Taunton Press.  Newtown, Connecticut.  1990.

Hoffmann, Per, Adya Singh, Yoon Soo Kim, Seung Gon Wi, Ik-Joo Kim, and
Uwe Schmitt.  “The Bremen Cog of 1380: An Electron Microscopic Study of
its Degraded Wood Before and After Stabilization with PEG.”  In
Holzforschung Vol 58 No 3 2004 pp 211-218

Hoffmann, Per and Mark Jones.  “Structure and Degradation Process for
Waterlogged Archaeological Wood”  in Archaeological Wood Properties,
Chemistry, and Preservation
. Developed from a symposium sponsored by the
Cellulose Paper and Textile Division at the 196th National Meeting of
the American Chemical Society, Los Angeles, California, September
25-September 30, 1988. Advances in chemistry series 225. American
Chemical Society. Washington 1990.

Hoffmann, Per.  ” On the Stabilization of Waterlogged Oakwood with PEG
II Designing a Two-Step Treatment for Multi-Quality Timbers.”  Studies
in Conservation
31 (1986) pp.103-113

Hoffmann, Per. “On the Stabilization of Waterlogged Oak with PEG –
Molecular Size Versus Degree of Degradation.”  Waterlogged Wood Study
and Conservation, proceedings of the 2nd ICOM Waterlogged Wood Working
Group Conference, Grenoble, France.  1984.  pp. 243-252.

Hoffmann, Per.  “Chemical Wood Analysis as a Means of Characterizing
Archaeological Wood” In book. Proceedings of the ICOM Waterlogged Wood
Working Group conference: Ottawa, 15-18 September 1981. ICOM Waterlogged
Wood Working Group (1982), pp.73-84.

Hoyle, Robert J. “Relating Wood Science and Technology to the Conservator” In Pacific Northwest Wet Site Wood Conservation Conference, September 19-22 1976 vol 2 pp 99.

Jagels, Richard.  “A Deterioration Evaluation Procedure for Waterlogged Wood.”   In book. Proceedings of the ICOM Waterlogged Wood Working Group conference: Ottawa, 15-18 September 1981.  ICOM Waterlogged Wood Working Group (1982), pp. 69-72

Jeberien, Alexandra and Malcolm Bilz.  “Comparison of Air Dried and
Freeze Dried Solutions of Polyethylene Glycol 3350”  In ICOM WOAM
Newsletter No. 31 June 2000.

Jensen, Poul; Grethe Jorgensen, Ulrich Schnell.  “Dynamic LV-SEM
Analyses of Freeze Drying Processes for Waterlogged Wood”  Proceedings
of the 8th ICOM Group on Wet Organic Archaeological Materials
Conference, Stockholm, 11-15 June 2001
Pub.  2002 pp.319-333

Johns, Dilys A.  “Observations Resulting from the Treatments of Waterlogged Wood Bowls in Aoteroa (New Zealand) in Hidden Dimensions 1998. pg 317.

Lindblad, Cecilia and Ingmar Persson. “Polyethylene Glycol/ Polyethylene
Oxide: An Overview of the Physical-Chemical properties of PEG/PEO”
Presented at the ICOM-CC Working Group on Wet Organic Archaeological
Materials in Amsterdam, 2007.  Not yet published.

 MacLeod, I. D., Kenna C., 1990. Degradation of Archaeological Timbers
by Pyrite: Oxidation of Iron and Sulphur Species” Proceedings of the 4th
ICOM Group on Wet Organic Archaeological Materials Conference
, ed. P.
Hoffman, Bremerhaven: ICOM, Committee for Conservation, Working Group on
Wet Organic Archaeological Materials, pp. 133-142.

Masuzawa, Fumitake and Yoichi Nishiyama.  “Experiments on the
Impregnation of Waterlogged Wood with PEG Part II”  Conservation Science
Bulletin
.  Hozon Kagaku Kentyushitsu Kiyo.  Vol. 3 1974 pp39-46 (this is
from a literature review in ICOM-CC WOAM Newsletter No 8 Nov 1982.)

Masuzawa, Fumitake and Matsuda Takatougin.  “Surface Treatment for the
Removal of Dark Hue on Waterlogged Wood Impregnated with PEG.”
Conservation Science Bulletin.  Hozon Kagaku Kentyushitsu Kiyo.  Vol. 3
1974 pp 47-51  (this is from a literature review in ICOM-CC WOAM
Newsletter No 8 Nov 1982.)

Masuzawa, Fumitake.  “Change of Waterlogged Wood Impregnated with PEG
Along the Lapse of Time.”  Conservation Science Bulletin.  Hozon Kagaku
Kentyushitsu Kiyo.  Vol. 3 1974 pp. 52-58  (this is from a literature
review in ICOM-CC WOAM Newsletter No 8 Nov 1982.)

Murray, Howard. “General Discussion Period Session II Analysis and
Classification of Wood.”  Proceedings of the ICOM Waterlogged Wood
Working Group Conference Ottawa 1981
.  pp.117-121

Rey, Louis Rene, Louis Rey, and Joan Christine May.  Freeze Drying/
Lypholization of Pharmaceutical and Biological Products
.  Informa Health
Care, 2004. Web version of 2nd edition.

Rodgers, Bradley.  ECU Conservator’s Cookbook: A Methodological Approach
to the Conservation of Water Soaked Artifacts
.   Chapter 2: Waterlogged
Wood.  Herbert P. Paschal Memorial Fund Publication.  East Carolina
University.  1992.

Singley, Katherine R. “The Recovery and Conservation of the Brown’s
Ferry Vessel” In book. Proceedings of the ICOM Waterlogged Wood Working
Group conference: Ottawa, 15-18 September 1981
.  ICOM Waterlogged Wood
Working Group (1982), pp. 57-60

Storch, Paul.  “Non-Vacuum Freeze-Dry Treatment of Two Leather Objects.” in Leather Conservation News. Vol 13 no 2. 1997. pg 15-17.

Viduka, Andrew.  Survey of Methods Used by Some Large Institutions
Specializing in the Conservation of Wet Organic Archaeological
Materials
.  Report as the 2002 Churchill Fellow: Winston Churchill
Memorial Trust of Australia.  2002.
http://www.churchilltrust.com.au/res/File/Fellow_Reports/Viduka%20Andrew
%2020021.pdf
.

Watson, Jacqui. “The Application of Freeze-Drying on British Hardwoods
from Archaeological Excavations.”  Proceedings of the ICOM Waterlogged
Wood Working Group Conference Ottawa 1981
. pub 1982

Young, Gregory S. and Richie Sims. “Microscopical Determination of PEG
in Treated Wood – the Effect of Distribution on Dimensional
Stabilization.”  Conservation of Wood and Metal: Proceedings of the ICOM
Conservation Working Group on Wet Organic Archaeological Material and
Metals.
 Freemantle, Western Australia Museum. 1987  Pub 1989. pp109-140

Young, Gregory S. “Polyethylene Glycol Localization within the Structure
of Waterlogged Wood.”  9th International Congress on Science and
Technology in the Service of Conservation.
 1982.

Young, Gregory S and Ian N.M. Wainwright. “Polyethylene Glycol
Treatments for Waterlogged Wood at the Cell Level.”  In book.
Proceedings of the ICOM Waterlogged Wood Working Group conference:
Ottawa, 15-18 September 1981
.  ICOM Waterlogged Wood Working Group
(1982), pp107-116

 

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PEG Summary: Alaska State Museum

April 4, 2009

This weblog includes several posts (some in draft form) that reflect my notes regarding PEG (polyethylene glycol) treatment for waterlogged wood.  The posts, when complete, will include:

1) PEG Summary: Alaska State Museum (this post)

2) PEG Bibliography Annotated (with Dana Senge)

3) PEG Shipwrecks

4) PEG Basketry (with Dana Senge)

5) What Do We Know About PEG?

6) Waterlogged Wood Deterioration

7) PEG Adhesives

8 ) Early PEG Treatments at the Alaska State Museum

All of these will be incomplete, but are the extent of my notes and investigations to get the Alaska State Museum lab up-to-speed for PEG treatment.  Since it has taken me WEEKS of reading and pondering over the past two years, it seems that this effort might be useful to others in a public forum like this blog.  Conservator Dana Senge (DKS Conservation) is also grappling with these issues and we’ve teamed up to share our observations and investigations.  Dana will be treating a wet basket excavated recently on the property of the Baranov Museum in Kodiak, Alaska.  I would imagine if she gets up to speed on PEG, she will be an excellent resource for people who have this kind of material that needs to be treated since she is a conservator in private practice.  CCI treats some of this kind of material, but only from Canadian sites and only those that they have the resources to commit to.

The Alaska State Museum has several baskets from a Baranof Island site that are in water, dated around 4, 000 years old.  Probably spruce root.  One basket from this group, as well as the even older Thorne River basket, have already been treated.  The protocol, recommended by CCI more than 10 years ago, preserved the baskets but has left them fragile and impossible to handle, exhibit or travel.  Perhaps travel will never be possible, but there is a great desire (especially among weavers) to have them travel to communities in Southeast Alaska.  To that end, I am looking into variations on the PEG treatment to make the remaining baskets more robust, as well as methods to further consolidate the surfaces of the baskets already treated.  I am nearing the end of a test of higher mw PEGS in samples of the yet-untreated archaeological material.  I am still rather early in the testing of possible consolidants but am focusing on the use of an asthma nebulizer for application.

There are certain aspects of the PEG literature that I am not looking at too closely.  One is freeze-drying, since we don’t have a freeze drier.  I am not completely clear what is happening, however, in just using a low temperature tissue freezer (-35C)  I am guessing that there is a bit of freeze-drying that happens, since the basketry does lose weight in the freezer, but that perhaps there is also some evaporation of liquid water with the subsequent controlled slow-drying?  I am also not particularly concerned with biocides, since we are using small quantities of PEG with these small artifacts and we can jsut make up a fresh batch if we have biological growth.  I suppose this might affect biological activity that I can’t see, but I have a gut-level instinct that adding in more chemicals makes the whole PEG-wood-water system even more complicated and unpredictable?  Ditto with including anti-oxidants, although I still worry about oxygen accelerating the breakdown of PEG over time.  And then there is the issue that these baskets might have iron in them that would eventually produce acids…should I be trying to remove that iron first?  The poor baskets have been waiting for treatment for 10 years now.  Part of me just wants to get ON WITH IT ALREADY!  Don’t be such a chicken!  But there are always more articles to read, more people to talk to…how many people in the world really understand PEG treatment after all?  Just a handful, I’m sure, can really grapple with all these variables.  And those few people can’t treat everything that is out there, although they have been heroic in the publications they have produced.


Waterlogged Wood Deterioration

April 4, 2009

WATERLOGGED WOOD DETERIORATION

Notes for investigating possible treatment of waterlogged archaeological spruce root basketry

Ellen Carrlee, March 2009

 

WOOD BASICS (especially conifers)

Gymnosperms (Softwoods) Seeds NOT in ovules.  Usually have needles.  Conifers in this group.  They have sieve cells, a type of phloem characteristic of non-flowering vascular plants.

Angiosperms (Hardwoods) Seed in ovules.  Flowering plants.  Usually lose leaves seasonally.  Divided into monocotyledons (grasses, palms, bamboo) and dicotyledons

 

 

Cell Wall has layers of:

1. cellulose (a polysaccharide aka complex carbohydrate aka complex sugar), cellulose will form H-bonds with about 36 other chains to form a microfibril, sort of like making a thick rope from thin fibers.  Some regions of these microfibrils are crystalline and some are amorphous.  They are 5-12nm wide and have tensile strength of steel. About 40-80% of the secondary cell wall is cellulose microfibrils (Bidlack et al 1992.)

2. hemicellulose a polysaccharide more soluble than cellulose…especially soluble in strong alkali.  Hemicellulose is now called cross linking glycans by biologists.  They don’t aggregate and don’t form microfibrils. Thought to cross link non-cellulosic and cellulosic polymers.  About 10-40% of the secondary cell wall is hemicellulose (Bidlack et al 1992.)

3. lignin (a complex polysaccharide)  is basically a polymer of phenolics, especially phenylpropanoids.  About 5-25% of the secondary cell wall is lignin, and the cellulose microfibrils and hemicellulosic chains are embedded in lignin, which serves as a amorphous polymer “glue.” Lignin % is higher in conifers than hardwoods in general.  Lignin is not easily soluble, and is probably bound chemically to the hemicellulose and not the cellulose.  Lignin is the precursor to coal (Bidlack et al 1992.)

 

The outermost layer of the cell wall is the middle lamella, and has the glue that binds it to adjacent cells.  The primary wall is thin, found in young, growing cells, and has pectic polysaccharides (30%), hemicellulose (25%) cellulose (15-30%) and protein (20%.)  All plant cells have a middle lamella and a primary wall.   Secondary wall is an additional deposit inside the primary wall.  Mostly for support and made of cellulose and lignin.  In the secondary cell wall, elongation stops during growth because of deposition of lignified secondary cell wall.  There are often distinct layers (S1, S2, S3) that differ in orientation of the cellulose microfibrils.  Lignin rarely occurs in the S3 lamella (Bidlack et al 1992.)  The lumen is the space bound by the cell wall.  The wall is made from the outside in, so as the wall gets thicker the lumen gets smaller.

 

Organelles are parts of the cell that do activities.  Include nucleus, cytoplasm, mitochondria, plastids, ribosomes, dictysomes, microtubules, vacuoles (water-filled part of the plant), endoplasmic reticulum.

 

Ergastic Substances are passive products of organelles (?)  Include starch, tannins, proteins, lipids, crystals/phytoliths (sometimes survive and aid ID.) 

Cutin is the lipid in the cuticle layer.  Suberin is the lipid in the Casparian strip, often in roots and periderm.  Cutins and suberins are persistent in nature.  Suberin is a physical barrier to water.

 

Plant tissues divide into

1)       Simple, like pith (ground tissue in the center of a stem or root) which is made of parenchyma cells.  Parenchyma are simple tissues, but come in a wide range of shapes and sizes with different functions.

2)       Compound, like vascular tissue which is made of both parenchyma and sclerenchyma cells.  Sclerenchyma are compound tissues divided into sclereids (ie stone cells) that are bigger diameter and have a thicker cell wall and fibers that are long and thin with pointed tips and a small lumen.  Both of these have multilayered birefringent walls. Sclerenchyma are thick walled, dead at maturity and give rigid support.  Note: Douglas fir sclereids are elongated and resemble fibers.

3)       Complex, like the bark, which is made of parenchyma, sclerenchyma, and collenchyma cells

 

Vascular tissue is the xylem and phloem

Epidermis is cuticle has cutin, lipids, oils, resins.

Periderm is the outer protective and supportive secondary tissue, formed by the cork cambium and it replaces epidermis in the stems and roots, mostly. Bark is periderm. Some of its parenchyma cells are called phellem and they contain a lot of suberin.

Ground tissue is everything BUT the vascular tissues, epidermis, and periderm, like cortex and pith.  AKA “fundamental tissue”

 

 

Xylem is the vascular tissue for water movement and has lignified secondary cell walls and pits in the cell wall.  Secondary xylem is wood, and preserves better than phloem.  Also sections nicely for detailed analysis.  Xylem is usually larger than phloem. Sapwood is the living secondary xylem and has starch grains.  Heartwood is dead, and contains extractives making it darker.  It is less porous than sapwood because it includes tyloses, tannins, salts, resins, silica etc that block fluid movement.  Growth rings are the result of early wood (larger tracheary elements and thinner walls.  More holes.) and late wood (smaller tracheary elements and thicker walls. Denser.)

 

Xylem is made of cell types:

  1. tracheids Found only in softwood, transport water and dissolved minerals and have thickened lignified walls for support.  Generally, loss of water through leaves drives the flow.  No perforations in end wall, but lots of pits in the walls.  Secondary thickenings of various kinds are diagnostic.  Spiral thickenings (like springs) appear only on Douglas fir and yew on the nothwest coast (but many other confiers worldwide).  Yew has steeper and less regular spirals and no resin canals.  Douglas fir has resin canals, but is not a true “fir” despite its vernacular name. DON’T confuse with spiral thickenings with spiral checking, which is more common in other conifers too. The tangential diameter helps ID of conifers (called “texture”.)  Big holes are “coarse” textured, like redwood.  ID chart on p.17 of Hoadley.  Nonliving cells.
  2. vessel members (aka trachea) Transport water in hardwoods.  These do have perforations in common end walls.. Secondary thickenings are also diagnostic. Nonliving cells
  3. fibers in hardwoods. Nonliving cells
  4. parenchyma Alive for many years

 

Secondary xylem in roots: vascular rays, periderm, vascular cambrium, vessel distribution, primary xylem.  Look carefully at ray anatomy, esp crossfield pitting and ray tracehids.

 

Phloem is the vascular tissue for food transport (sugars and amino acids) and has thin-walled cells with less lignin than the xylem.  Secondary phloem is inner bark for food storage and transport.  It contains layers of fibers alternating with sieve element cells and parenchyma cells.  Parenchyma cells (12-38% of inner bark volume) are thin walled and weak next to the stronger fibers of sclerenchyma and this is why inner bark separates into sheets.  Note: genus Pinus has no sclerenchyma.  Phloem contains mostly sieve elements and neighboring regulatory cells (“Sieve elements”/ albuminous cells in gymnosperms, “sieve tube elements”/ companion cells in angiosperms.) Sieve elements don’t survive well for ID, but are at least half the cells of the inner bark.  Sieve elements are a lot like tracheids but have sieve areas rather than pits.  In the cedar bark used for weaving, tissue is made up of stong hair like fibers, delicate cuboidal parenchyma cells that store food, and porous food conducting sieve cells. 

 

CONIFEROUS WOOD has

Axial tracheids with smooth walls or walls with spirals; circular bordered pits (CBP) with numerous rows.  Are like 100X longer than their diameter.  Almost all the longitudinal cells in conifers are this kind.

Ray tracheids that are smooth or dentate (in pines) Don’t show up in Western Red Cedar.

Axial ray parenchyma that are smooth or dentate

Axial parenchyma with smooth or nodular end walls.  Shorter than the tracheids.  Sometimes are filled up.  Don’t show up in pinus and picea.

Ray parenchyma with smooth or nodular endwalls (nodular in spruce root.)

Resin canals that are thick or thin walled.  Larger rounded opening that has thin-walled epithelial cells that secrete the resin (easily damaged in sampling.)  If it bulges and blocks the canal that’s called a tylosoid.  Pines have numerous, evenly distributed ones with thinner epithelial cells.  Firs and spruces have fewer, sometimes grouped, and thicker epithelial cells.  Can be hard to see in samples but important for ID.  Spruce root has large coalescent resin canals in the central region.

 

A ray initiates in the cambrium and extends radially into the secondary phloem and xylem.  (cross over the growth rings at 90degrees) Mostly made of parenchyma cells but also tracheids.  It shows up in the secondary xylem of some conifers.  Most other cells go parallel to the stem or trunk.  A fusiform ray has a larger resin canal in the middle that makes it look like an eye in tangential view, diagnostic for pine.  Rays are important in ID.  Upper and lower rows of ray cells are ray tracehids, and the middle ones are ray parenchyma. Ray tracheids can be hard to see in hemlock.

 

Pits are voids in the secondary cell wall.  It matches up with a pit in an adjacent cell, forming a pit pair.  Pits in longitudinal or ray parenchyma cells are simple pits.  Tracheids have more elaborate bordered pits, look like targets or donuts (they indicate you have a conifer.)  The number across the radial wall of earlywood tracheids is important for ID (one for spruce, two for larch, up to four in redwood.) 

 

Where ray parenchyma and tracheids intersect, you get field crossings and the pitting there has one of four shapes: piceoid (slit opening, as in spruce root,) cupressiod (oval, almond opening,) taxodioid (round, as in western red cedar,) fenestral (like a window, squarish)

 

ROOT: Similar to branches (withes) in the circular arrangement of cells.  But cells are larger, thinner walled, often collapsed, and tissue can have open/disorganized appearance.  Resin canals might join together.  Rows of bordered pits may be more numerous than typically found in trunk wood for that species.  Longitudinal parenchyma are very prominent, and the width of the ray parenchyma cells is bigger than in the rest of the tree.

 

DETERIORATION BASICS

 

WHAT DEGRADES

* Loss of holocellulose in waterlogged wood, because it is so soluble.  (Florian, 1990)

* Holocellulose degrades more rapidly than lignin, and hollocellulose in archaeological wooden arrows from Nyden Bog had decomposed completely. (Christiensen 2006)

* Holocellulose is the hemicellulose plus the cellulose, and it deteriorates first.  Umax is a function of deterioration in the form of holocellulose loss, and thus the void space in the cell wall.  Depends on the density of that species of wood.  (Cook and Grattan, 1986)

* Holocellulose = cellulose + hemicellulose.  As water content increases, carbohydrate decreases and you’re left with proportionally more and more lignin.  Lignin is quite resistant to microbial and chemical attack.  Cellulose and hemicellulose are lost at about the same rate, even though hemicellulose can be degraded much easier than the crystalline cellulose.  (Hoffmann 1982)

* Degraded oak timbers show about half of the cellulose and hemicellulose is gone, with fissures and cracks criss-crossing the tissue. (Hoffmann 1986)

* Lignin bonds only to hemicelluloses, not to celluloses.  Lignin is made of large 3_D crosslinked molecules.  (Hoffmann 1982.)

*  Wood shows zones of progressive degradation.  Secondary wall loosens because of hydrolysis of carbohydrates.  Cell walls lose fluorescence and birefringence.  (Does this impact the cobalt thiocyanate staining?) Lignin skeleton eventually collapses, leaving only granular debris.  Tertiary walls and compound middle lamellae keep the dimensions stable as long as they are filled with water (Hoffman & Jones 1988; Blanchette & Hoffmann 1994.) 

* Double bonds in lignin are affected by warm treatments (Christensen et al 2006)

* Chemical degradation of the secondary cell wall starts at the lumen and progresses inward (Hoffmann 1982)

* Western red cedar inner bark cell walls very thick.  Lumens in inner bark of Western Red Cedar were very small compared to those in wood.  Some smaller thinner-walled cells contain resins.  (Bilz et al 1998)

* In cedar bark (phloem) the fiber cells are usually intact, holes in sieve plates and pits are enlarged, pectin, starch bodies and inorganic crystals are gone, thin-walled parenchyma cells mostly gone, cellulose seems to be gone or changed.  Cell walls have a crystalline look that might be due to impregnation with inorganic salts from burial, perhaps an early stage of fossilization.  Some of the insoluble resins and tannins of the bark are still present in reduced amounts, and some of the color-inducing brown phlobaphenes are still there too.  High lignin and tannin content in the call walls of fibers and sieve cells. (Florian 1977)

* Study of the Bremen Cog (oak, fresh water) indicates wood cell walls are thinned, erosion bacteria were a primary agent of degradation, and that non-degraded tissues were impermeable to PEG 3000 and only impregnated with PEG 200. (Hoffmann et al 2004)

* Higher cellulose content is correlated to greater risk of fungus development. (Grattan 1986)

* Mold and sap-staining fungi eat starch in ray cells.  Spiral checking of tracheid and fiber cell walls often attacked by staining fungi.  Don’t mix up spiral checking with spiral thickening. (Jagels, 1982)

* Mold and sap stain fungi only utilize the food stored in the wood and do not destroy the strength (Florian 1977)

* Egg-shaped voids are typical of holes left by fungal hyphae (Hoffmann 1982)

 

* Surface cuboidal cracking is often due to soft-rot. (Florian 1982)

* Pectin is the main chemical in the membranous valves of bordered pits, and bacteria that specifically attack pectin are often the first to enter the wood, making it more permeable.  (Florian, 1977)

* Collapse of radial walls of tracheids when waterlogged in Thuja plicata is a weakness. (Florian 1982)

* Loss of pectin that normally glues cells together is often missing in deteriorated wood, which might contribute to cracks between the longitudinal cells and the stronger ray parenchyma cells. (Florian 1982)

* Tension wood is not characteristic of roots (Florian, 1982)

 

SHRINKAGE AND COLLAPSE

* Shrinkage from capillary tension happens when the free water is pulled by evaporation from the void structure of the wood.  Shrinkage is also caused from desorption of bound water from the cell wall.  Article gives extensive info about which cells collapse in which direction. (Barbour and Leney  1982)

* The meniscus of water (which has high surface tension) applies stress to those capillaries as it leaves and can collapse them.  Forces are not as intense if there are air bubbles, as in green wood. This is why wood that is only damp and not waterlogged can slowly air dry successfully, especially if the cell walls are not too degraded. (Grattan 1986.)

* Hygroscopically bound water in the capillary network of the cell walls needs to be replaced by PEG for dimensional stability to occur (Young, 1982)

* “Second order space” is the term used to describe the volume of the microcapillaries in the cell wall that does not include the voids caused by deterioration.  At the fiber saturation point, water exactly fills this space without filling the lumen in undeteriorated wood.  (Cook & Grattan 1990)

* Areas like roots that have a lot of longitudinal or ray parenchyma will have more shrinkage (Florian 1982)

* Salinity differences between water inside cells and outside of cells can cause problems with osmotic pressure if you put waterlogged material found in saltwater directly into fresh water.  Salt solution moving out of the cell moves faster than fresh water moving in and cell can collapse.  Desalination is crucial. (Bradley 1992)

* Shrinkage in sound or slightly deteriorated wood is anisotropic, or varies in the three major directions: longitudinal 0.5%, radial 3-6%, and tangential 5-10%.  More deteriorated wood ill show less well-defined shrinkage (but more shrinkage overall?) (McCawley 1977)

 

PENETRATION AND PERMEABILITY

*  Capillaries make up about 40% of the volume of the cell wall. Capillaries seem to range between 10-80nm.  Water is 0.2nm, PEG 400 molecule around 2nm x 0.25nm, PEG 1000 around 4.5nm and PEG 4000 around 18nm.  (Hoffmann 1982.)

* Intracell connections, “plasmodesmata” or “cytoplastmic connections” have small diameters.  Water and glucose (5-carbon ring) can pass, for example, but PEG and sucrose (6-carbon ring) cannot pass.  Osmotic pressure can also cause those openings to collapse and make PEG penetration harder.  Perhaps PEG 200 is the best for these spaces.  (Grant et al 1997.)

* Low mw PEG in cell lumina and larger voids in cell wall will diffuse back out of the wood again, only remains in the capillary system.  Larger mw needed for those larger voids (Hoffmann 1986.)

* Lower mw PEG penetrates the micro-capillaries of the cell wall, while higher mw penetrates the lumens, flows through the vascular system (Grattan 1986.)

* Normal anatomical wood characteristics that impede permeability: few/small hardwood vessels, many hardwood thick-walled fiber cells, short longitudinal tracheids in softwoods, the absence of ray tracheids, the absence of radial and longitudinal resin canals, aspirated and encrusted bordered pits, blind simple pits, high specific gravity, ray parenchyma containing resin or other material, reduced tangential wall pitting, extractives in heartwood.  (Florian, 1982)

* Pits between the cells have valves (the torus) which can block penetration of PEG if closed (aka blocked or aspirated.)  Must be viewed at 1000X to 3000X so requires SEM?  (Bradley 1992)

 

* In white oak, which is hard to penetrate, the rate of degradation by microorganisms is faster than their speed of penetration, so you get areas of very deteriorated wood on the exterior of the timbers and less deteriorated zones towards the core. (Christensen 1970, Grattan 1986)

* Pine and oak are two species where the heartwood is only slightly permeable to liquids, and often less degraded than outer areas of the wood (Hoffmann 1986.)

* Western Red cedar (thuja plicata) is very difficult to penetrate, even when deteriorated.  Similar to oak in this way.  (Cook and Grattan 1990)

*Picea sp and Thuja plicata have no tangential permeability because there aren’t many wall pits, there are blind pits and there’s resin in the ray parenchyma cells.  Picea will be more permeable than Thuja plicata because it has resin canals and ray tracheids that Thuja plicata does not.  (Florian 1982)

* In many coniferous species, fast-growing wood is more permeable than slow growth wood.

(Jagels, 1982)

* Softwood samples generally show open and enlarged tracheid bordered pits (probably from bacteria) which make them more porous (Florian 1982)

*  Deterioration greatly improves the ability of PEG to penetrate and treat wood successfully, but most excavated waterlogged wood is only moderately deteriorated.  White oak, various cedars, and white ash are hard to penetrate, while aspen, cottonwood, alder and spruce allow greater penetration. Caution with determining degree of deterioration from thin 3mm cross sectioned wafers of wood examined under the microscope, as the sample has a lot of disrupted wood cells and suggests more cell wall accessibility than there really is.   (Young, 1990)

 

MEASURING DETERIORATION

* Degree of deterioration in PEGCON determined by comparing the density of the deteriorated wood to the density expected for that species. 

* Percent water content is often used to evaluate deterioration of waterlogged wood, but it varies with species and is measured in different ways which makes comparisons difficult (Grattan 1986.)

* Archaeological woods have a higher ash content, which means they have more minerals in them than fresh wood.  Minerals are determined as oxides after their organic content has been burnt away in analysis. (Hoffmann 1982)

* Some waterlogged wood, Mary Rose, Brown’s Ferry Wreck, show elevated ash content.  Also, metals and siliceous materials enter the wood and add to the ash content.  (Richard Clarke comment in  Singley, 1982.)

* A device called a Pilodyn has a spring loaded blunt pin and helps to determine degree of deterioration on large things like timbers from the Mary Rose. but it is far too large for basketry (Grattan 1986)

* Amount of water in waterlogged wood is calculated: weight of wet wood minus weight of oven dried wood divided by weight of the oven dried wood and multiplied by 100 to give % water.  Anything over 200% is considered degraded.  (Hamilton 1998)

 

Sources:

Alden, Harry.  Plant Anatomy and Morphology for Objects Conservators and Archaeologists.  CD from a course offered by Smithsonian Center for Materials Research and Education, 2000.

 

Barbour, R.J. and L. Leney.  “Shrinkage and Collapse in Waterlogged Archaeological Wood: Contribution III Hoko River Series.  In book. Proceedings of the ICOM Waterlogged Wood Working Group conference: Ottawa, 15-18 September 1981. ICOM Waterlogged Wood Working Group (1982), pp. 209-225.

 

Barbour, James.  “The Condition and Dimensional Stabilization of Highly Deteriorated Waterlogged Hardwoods.”  Proceedings of the 2nd ICOM Waterlogged Wood Working Group Conference.  Grenoble, 28-31 August 1984. 

Lots of info about the layers of the cell wall

 

Bernick, Kathryn.  Personal communication April 9, 2009.

 

Bidlack, Jim, Mike Malone, and Russel Benson.  “Molecular Structure and Component Integration of Secondary Cell Walls in Plants.”  Proceedings of the Oklahoma Academy of Science Vol 52 1992 pp 51-56.

 

Bilz, Malcolm, Tara Grant and Gregory S. Young.  “Treating Waterlogged Basketry: A Study of Polyethylene Glycol Penetration Into the Inner Bark of Western Red Cedar.”  Proceedings of the 7th ICOM-CC Working Group on Wet Organic Archaeological Materials Grenoble 1998.  pp.249-253

 

Blanchette, Robert A.; Hoffmann, Per “Degradation processes in waterlogged archaeological wood”  Proceedings of the fifth ICOM Group on Wet Organic Archaeological Materials conference, Portland, Maine, 16-20 August 1993 pub. 1994

 

Christensen, M, M. Frosch, P. Jense, U. Schnell, Y. Shahsoua, O.F. Nielsen. “Waterlogged Archaeological Wood, Chemical Changes by Conservation and Degradation.”  Journal of Raman Spectroscopy.  Vol. 37, issue 10.  Special Issue: Raman Spectroscopy in Arch and Archaeology II. 2006.  pp. 1171-1178.

 

Christensen, B. “The Conservation of Waterlogged Wood in the National Museum of Denmark.”  Museums Tenniske Studier 1, National Museum of Copenhagen, Denmark.  1970.

 

Cook, Clifford and David Grattan.  “A Method of Calculating the Concentration of PEG for waterlogged Wood.”  Proceedings of the 4th ICOM Group on Wet Organic Archaeological Materials.  Bremerhaven 1990.

 

Florian, Mary-Lou E., Dale Paul Kronkright, Ruth E. Norton.  The Conservation of Artifacts Made from Plant Materials.  J. Paul Getty Trust.  1990.

 

Florian, Mary-Lou.  “Anomalous Wood Structure: A Reason for Failrure of PEG in Freezer-Drying Treatments of Some Waterlogged Wood from the Ozette Site.”  In book. Proceedings of the ICOM Waterlogged Wood Working Group conference: Ottawa, 15-18 September 1981.  ICOM Waterlogged Wood Working Group (1982), pp85-98

 

Florian, Mary-Lou.  “Waterlogged Artifacts: the Nature of the Materials.  Journal of the Canadian Conservation Institute.  1977

 

Grant, Tara and Malcolm Bilz.  “Conservation of Waterlogged Cedar Basketry and Cordage.”  Proceedings of the 6th ICOM Group on Wet Organic Archaeological Materials York, 1996. Pub 1997

 

Grattan, D. “Some Observations on the Conservation of Waterlogged Wooden Shipwrecks.”  AICCM Bulletin, Vol. 12 No 3 and 4. 1986.

 

Hamilton, Donny L. Methods of Conserving Archaeological Material from Underwater Sites.  Nautical Archaeology Program Department of Anthropology Texas A&M University.  1998.

 

Hoadley, R. Bruce. Identifying Wood.  Accurate Results with Simple Tools.  Taunton Press.  Newtown, Connecticut.  1990.

 

Hoffmann, Per, Adya Singh, Yoon Soo Kim, Seung Gon Wi, Ik-Joo Kim, and Uwe Schmitt.  “The Bremen Cog of 1380: An Electron Microscopic Study of its Degraded Wood Before and After Stabilization with PEG.”  In Holzforschung Vol 58 No 3 2004 pp 211-218

 

Hoffmann, Per and Mark Jones.  “Structure and Degradation Process for Waterlogged Archaeological Wood”  in Archaeological Wood Properties, Chemistry, and Preservation. Developed from a symposium sponsored by the Cellulose Paper and Textile Division at the 196th National Meeting of the American Chemical Society, Los Angeles, California, September 25-September 30, 1988. Advances in chemistry series 225. American Chemical Society. Washington 1990.

 

Hoffmann, Per.  “ On the Stabilization of Waterlogged Oakwood with PEG II Designing a Two-Step Treatment for Multi-Quality Timbers.”  Studies in Conservation 31 (1986) pp.103-113

 

Hoffmann, Per. “On the Stabilization of Waterlogged Oak with PEG – Molecular Size Versus Degree of Degradation.”  Waterlogged Wood Study and Conservation, Proceedings of the 2nd ICOM Waterlogged Wood Working Group Conference, Grenoble, France.  1984.  pp. 243-252.

 

Hoffmann, Per.  “Chemical Wood Analysis as a Means of Characterizing Archaeological Wood” In book. Proceedings of the ICOM Waterlogged Wood Working Group conference: Ottawa, 15-18 September 1981. ICOM Waterlogged Wood Working Group (1982), pp.73-84.

 

Jagels, Richard.  “A Deterioration Evaluation Procedure for Waterlogged Wood.”   In book. Proceedings of the ICOM Waterlogged Wood Working Group conference: Ottawa, 15-18 September 1981.  ICOM Waterlogged Wood Working Group (1982), pp. 69-72

 

Martin, Robert and John G. Christ.  “Elements of Bark Structure and Terminology.”  Wood and Fiber  Vol 2 No 3 1970.  pp 269-279.

 

McCawley, J.C. “Waterlogged Artifacts: The Challenge to Conservation.”  In Journal of the Canadian Conservation Institute.  Vol 2, 1977. pp17-26.

 

Rodgers, Bradley.  ECU Conservator’s Cookbook: A Mthodological Approach to the Conservation of Water Soaked Artifacts.   Chapter 2: Waterlogged Wood.  Herbert P. Paschal Memorial Fund Publication.  East Carolina University.  1992. 

 

Saupe, Dr. Stephen G.  “Cell Walls –Structure and Function” Plant Physiology (biology 327) College of St. Benedict/ St. john’s University. Collegeville, Minnesota. 2009.  http://employees.csbsju.edu/ssaupe/biol327/Lecture/cell-wall.htm

 

Singley, Katherine R. “The recovery and conservation of the Brown’s Ferry vessel” In book. Proceedings of the ICOM Waterlogged Wood Working Group conference: Ottawa, 15-18 September 1981.  ICOM Waterlogged Wood Working Group (1982), pp. 57-60

 

Young, Gregory S.  “Microscopy and Archaeological Waterlogged Wood Conservation.”  CCI Newsletter, No. 6, September 1990.  pp 9-11.

 

Young, Gregory S. “Polyethylene Glycol Localization within the Structure of Waterlogged Wood.”  9th International Congress on Science and Technology in the Service of Conservation.  1982.


PEG Shipwrecks

April 4, 2009

PEG-TREATED SHIPWRECKS (listed from oldest ships to youngest)

Incomplete list, a starting point

by Ellen Carrlee Conservator Alaska State Museum

March 30, 2009

 

 

Ship Name: Bercy Dugout Canoe

Location: SE Paris, paleochannel near River Seine.  (Exhibited Musee Carnavalet)

Date Sank: 3900 BC (some say 4,900 BC)

Date Salvaged: 1990’s

Conservator:  Arc-Nucleart Grenoble France

Background:  Made of oak, very poor condition, PEG 4000 for 9 months.  Mount made of polyester resin.

Source:  Arc-Nucleart website http://www.arc-nucleart.fr/an/offre/boiseaux.htm

 

Ship Name: Ma’agan Mikhael Ship

Location: Coast of Israel 35km south of Haifa

Date Sank:  400BC

Date Salvaged: 1988-89

Conservator:  University of Haifa, Ya’acov Kahanov

Background:  Treatment completed by 1996, now on exhibit.  Hull dismantled at sea. Pinus brutia hardwood and Quercus sp. Softwood.  Two-stage treatment, PEG 400 up to 45% and then PEG 3350 up to 100%.  Shrinkage was 2.8% with dimensions of ship within a centimeter of those recorded on wreck before salvage. 

Source: Kahanov, Ya’acov “Wood Conservation of the Ma’agam Mikhael Ship”  International Journal of Nautical Archaeology.  Vol. 26.  No. 4.  1997 pp316-329. 

 

Ship Name: Kyrenia

Location: Cyprus

Date Sank: 300BC

Date Salvaged: 1967-74

Conservator:  Michael Katzev

Background:  Pine?  Katzev was a classical archaeologist and according to conservator George Bass, he was the first to take a Mediterranean shipwreck hull through conservation and put on display.  Some sources say it was treated with PEG, a few months for smaller pieces and a few years for larger ones, but I can’t find the % or mw used, need to get the Katzev article.  Apparently, it was reconstructed after PEG treatment.

Source:  http://www.abc.se/~m10354/uwa/wreck-br.htm

Katzev, M.L. “Conservation of the Kyrenia Ship 1971-72”  National Geographic Society Research Report.  Vo. 12 pp. 417-426.

 

Ship Name: Marsala Punic Ship

Location: Marsala, Italy (Palermo Archaeological Museum)

Date Sank: circa 241 BC

Date Salvaged: 1971-75

Conservator:  Pietro Alagna

Background: Oak, pine, and maple.  Hull dismantled to fit into tanks.  Treated with PEG 4000 up to 80% for 250 days (a little more than 8 months) at 60C.  In preliminary tests, a piece of maple had done better treated with PEG 1200 first and then PEG 4000.

Source:  Alagna, Pietro.  “The Construction of the Treatment Tanks Used in the Conservation of the Wood of the Marsala Punic Ship.” Studies in Conservation Vol. 22.  1977 pp 158-160.

 

Ship Name: Thracian one-log boat

Location:

Date Sank: 200 BC?  Bronze Age

Date Salvaged: early 1970’s

Conservator: Anton Mihailov

Background:  Abstract from BCIN describes an accelerated (262-day) treatment for dugout Thracian canoe of Mountain ash (Fraxinus excelcior). Preliminary wetting in a 1% PEG 1500 bath with 0.2% sodium pentachlorophenolate as a biocide, gradually increasing the PEG 1500 concentration to 30% and the biocide concentration to 0.5%; as the concentration of PEG was increased to 40%, 20% PEG 4000 was included; as the concentration of PEG was increased further, the proportion of PEG 4000 was raised and glycerine added in amounts ranging from 0. 5% up to 2%. Temperature was elevated to 64°C, PEG concentration was stabilized at 85% and cooled to 50°C (122°F); cleaning by means of heat, ethanol and methylated spirits is described, as well as post-cleaning surface treatment with Cosmoloid microcrystalline wax, Paraloid B 72 and toluene.  Also treated another dugout canoe of oak in 1972 ICOM report using PEG 3000 for 475 days.

Source: Anton, Mihailov. “Conservation of a Thracian one-log boat.”  In book. ICOM Committee for Conservation 5th triennial meeting: Zagreb, 1-8 October 1978: preprints. International Council of Museums (1978)

 

Ship Name: Gallo-Roman Boats of Pommeroeul

Location: Pommeroeul, Belgium

Date Sank:  100-200 CE

Date Salvaged: 1978-82

Conservator:  Eddy DeWitte, Alfred Terfve, Jozef Vynckier and others

Background:  Wooden river boats made from green oak with no sapwood.  Stored for 5 years, impregnated with PEG 4000 at 65C in a tank for 2 years.  Reassembled by Michael Esnault, Patrick Chasse, Philippe Duhaut working under Alfred Terfve.

Source:  De Witte, E., A. Terfve, and J. Vynckier.  “The Consolidation of the Waterlogged Wood from the Gallo-Roman Boats of Pommeroeul.”  Studies in Conservation Vol. 20 No. 2.  1984.  pp. 77-83.

 

Ship Name: Prow of Roman boat from Marseilles

Location: Place Jules Verne Marseilles, France

Date Sank: 200-300 CE

Date Salvaged: ?

Conservator:  Arc-Nucleart Grenoble, France

Background: Treated with PEG 400 and 4000.  Elaborate mountmaking for exhibit

Source:  Arc-Nucleart website http://www.arc-nucleart.fr/an/offre/boiseaux.htm

 

 

Ship Name: Gallo-Roman Barge from Yverdon-les-Baines

Location: Yverdon-les-Baines, Switzerland

Date Sank: 400CE

Date Salvaged:  1984

Conservator:  Gilbert Kaenel?

Background:  Made of oak.  Removed whole, treated with PEG 4000 15-85% at 60C.  Museum look is said to be “high quality natural finish”

Source:  Kaenel, G. “PEG conservation of a Gallo-Roman barge from Yverdon-les-Bains (Canton of Vaud, Switzerland).” In Hoffmann, Per, ed. Proceedings of the ICOM Group on wet organic archaeological materials conference, 5 (Portland/Maine, 1993). Bremerhaven : ICOM, 1994.  pp143-163.

 

Ship Name: Shinian Ship (Chinese vessel)

Location: Shinian, SW Coast of Korea near Jeunglo Island

Date Sank:   1000-1100 (11th Century Yuan Dynasty)

Date Salvaged: 1976-1984

Conservator: Mokpo Conservation Center, est.1981

Background: Red pine.  5% PEG 400 at room temp, discarded when smelly, increased by 5% PEG 400 every 3-4 months until 20%.  Tried removal of iron around nail holes etc mechanically and with EDTA but not satisfactory.  Heated up to 40 degrees C (104F): 25% PEG 4000 increased 5% evert 2-3 months until 70-80% total.

Source:  ICOM-CC WOAM Newsletter No 19 March 1990 pp9-11.

http://www1.icom-cc.org/Documents/WorkingGroup/WOAM/Newsletter19.pdf

 

Ship Name: Skuldelev Viking Ships

Location: Roskilde, Denmark

Date Sank: 1070

Date Salvaged: 1962

Conservator:  B. Brorson Christensen  National Museum of Denmark

Background: 5 ships intentionally sunk in a narrow channel as a barricade protecting the trading town of Roskilde.  Viking Ship Museum built in 1969.  1970 publication: they began with 10% PEG 4000by weight, raised to 60C. Addition of more in small amount daily.  Small finds were done in 7 months, but timbers had distortion at that duration and longer time was needed for them, usually 12-24 months. Pine did well but oak still had some collapse. 

Analysis indicates that PEG has not broken down to a lower MW in 40 years?  Large amounts of PEG could be extracted from degraded parts of the ships but hardly any from sound parts. Mass spectrometry showed that PEG 4000 is present only in the surface layers of the wood, PEG 1500 and PEG 600 are present at all depths of the wood that has been treated with it. Low molecular weight PEG was detected in one of the Skuldelev ships by mass spectrometry and Size Exclusion Chromatography (SEC), it is argued that this is due to degradation of PEG 4000. SEC also showed that PEG 600 is the major PEG component in the Vasa which makes this particular object sensitive to changes in air humidity since PEG 600 is hygroscopic.

Grattan and Clarke: Christensen overlooked the use of low mw PEG.  He did do some testing of enzyme to improve permeability.  Difficulty of the tyloses in vessels in the oak heartwood blocking penetration.  Also tried the use of PEG in solvents.  Other issues have arisen, as described in 2002 publication. 

Source:  http://www.abc.se/~m10354/uwa/skuldele.htm

Motensen, Martin Nordvig, Egsgaarde Helge,  Søren Hvilsted, Yvonne Shashoua, Jens Glastrup.  “Characterisation of the Polyethylene Glycol Impregnation of the Swedish Warship Vasa and one of the Danish Skuldelev Viking Ships”  Journal of Archaeological Science. Vol.34, No8,2007.  pp. 1211-1218

 

Crumlin-Pedersen, Ole and Olaf Olsen The Skuldelev Ships I  Roskilde Viking Ship Museum and the National Museum of Dernmark.  2002.  Review online of the book includes useful info:

http://findarticles.com/p/articles/mi_hb275/is_1_76/ai_n29095450

 

Grattan, D.W. and R.W. Clarke.  “Conservation of Waterlogged Wood.”  In, Conservation of Marine Archaeological Objects. Ed Colin Pearson.  Butterworth. London and Boston. 1987. 164-206   

 

Christensen, B. Brorson.  “The conservation of waterlogged wood in the National Museum of Denmark. With a report on the methods chosen for the stabili zation of the timbers of the viking ships from Roskilde Fjord, and a report on experiments carried out in order to improve upon these methods” Studies in museum technology, National Museum of Denmark Copenhagen 1970.

 

Ship Name: Bremen Cog

Location: Bremer, Germany  Weser River (Deutsches Schiffahrtsmuseum)

Date Sank: 1380

Date Salvaged: 1963

Conservator:  Per Hoffmann

Background: Found during dredging for new dock in 1962.  2-step PEG treatment for 19 years.  Reassembled and a tank built around it for total submersion.  Tank cut away after treatment.  1985-1995 PEG 200.  1995, switched to PEG 3000 up to 63%.  Treatment ended in 1999.  Note, it was found in fresh water and is not suffering the acid issue of the Vasa.

Source:  http://www.dsm.museum/MA/cog.htm.  Also, many articles written by Per Hoffmann

 

Ship Name: Mary Rose

Location: Portsmouth, England

Date Sank: 1545

Date Salvaged: 1982

Conservator: Mary Rose Trust

Background:  Oak with elm keel.  Almost the entire starboard side was salvaged.  3,000+ timbers were recovered and placed in storage.  Treatment did not begin until 1994, with spraying of PEG 200 up to 40% until 2005 and then PEG 2000 currently aiming to continue until 2011 and increase to final concentration of 50-60%.  Suffering from sulfur and acid problems like the Vasa, but luckily still in a wet treatment phase.

Source:  http://www.physics.uoguelph.ca/summer/scor/articles/scor161.htm.

http://ssrl.slac.stanford.edu/research/highlights_archive/maryrose.html.

http://www.pnas.org/content/102/40/14165.full

Unger, Achim; Schniewind, Arno P.; Unger, Wibke  Conservation of Wood Artifacts : A Handbook.  Natural Science in Archaeology Series.  Springer Verlag  New York. 2001.

 

Ship Name: Vasa

Location: Harbor of Stockholm, Sweden.  Brackish salt water, very polluted

Date Sank: 1628

Date Salvaged: 1961

Conservator:  Swedish National Maritime Museums

Background: Brackish water not salty enough for shipworms, pollution killed a lot of bacteria

This was the first big PEG treatment for a shipwrecked hull, sprayed for 17 years

1962-1971 sprayed with PEG 4000 and PEG 1500

1971-1979 PEG 600 for better penetration

From 1965-1971 PEG solution was continuously recirculated.  Concentration never over 45%.  Final hand sprayed coating of 45% PEG4000 then hot air to finish surface.

 

In 2000 acid problem discovered.  PEG corrodes iron, and the iron catalyzes oxidation of sulphur to make sulfuric acid.  The sulphur was made by bacteria in an anaerobic environment.  Bacteria take sulphur from seawater and reduce sulphate ions to hydrogen sulphide.  Early on, spraying with Borax (5 tons) to kill bacteria helped neutralize the acid, since Borax is alkaline.  Now, they are considering using chelating agents to complex the iron.  EDMA complex is orange, but works a lot better than DTPA. 

This issue apparently is happening to a lot of shipwrecks treated with PEG, except for the Bremen Cog which was found in freshwater?  MW of the PEG 30 years later seems to be similar.  Also issues with formic and acetic acids.  Formic may be related to the PEG, but acetic may be from the wood.

Source:  http://www.fos.su.se/~magnuss/peg.html.

 

 

Ship Name: Batavia (United Dutch East India Company)

Location: Freemantle, Western Australia

Date Sank: 1629

Date Salvaged: 1972-1976

Conservator:  Ian MacLeod, James Pang

Background:  Oak with Baltic pine sheathing, pine masts.  Could be fully immersed in PEG, since it was excavated in parts.  PEG 1450 was used, according to Grattan and Clarke. Up to 90% over 2-3 years at 60degreesC.  Surface was brushed with PEG 6000.  Issue of iron corrosion products as pyrite in timbers.  Deacidified with gaseous ammonia.  In 1990, surfaces were becoming fragile.

Source:  http://www.museum.wa.gov.au/collections/maritime/march/shipwrecks/Batavia/batavia.html.

Unger, Achim; Schniewind, Arno P.; Unger, Wibke  Conservation of Wood Artifacts : A Handbook.  Natural Science in Archaeology Series.  Springer Verlag  New York. 2001.

 

Grattan, D.W. and R.W. Clarke.  “Conservation of Waterlogged Wood.”  In, Conservation of Marine Archaeological Objects. Ed Colin Pearson.  Butterworth. London and Boston. 1987. 164-206   

 

Ship Name: LaBelle

Location: Matagorda Bay, Texas

Date Sank: 1687

Date Salvaged: 1996 (cofferdam)

Conservator: CRL at Texas A&M

Background: Began soaking in PEG in 2002?  1/3 of the ship survives.  They built a large outdoor vat covered with a greenhouse-like tent around 2001.  Ship was reassembled in the vat?

Source:  http://www.texasbeyondhistory.net/belle/laboratory.html

 

Ship Name:  Machault

Location: Restigouche River, Chaleur Bay (Restigouche National Historic Site Visitor Center, New Brunswick)  Canada.

Date Sank: 1760

Date Salvaged: 1969-1972

Conservator:  Parks Canada

Background:  Mostly made of oak.  David Grattan says, “The Machault in Canada, though ultimately successfully conserved with PEG, initially encountered problems when an untested sand drying process was tried out. This was in the early days of conservation in Canada.” After the sand drying didn’t work, they sprayed with 15% PEG 540 blend (1540 and 300).  Trials of 25% did not soak into the wood.  Schedule from 1977-1979 went: 4 months of 15%, 4 months 25%, 18 months 25% and 6 months 100% each time applied 3X per week.  Then they decided to apply thick molten PEG 540 directly to the timbers.  This was absorbed very quickly, and they continued at 6 month intervals.  They say the wood is not having trouble as of 1982, but they are concerned about fungicide sodium pentachlorophenate as high as 9000ppm.

Source:  http://cool-palimpsest.stanford.edu/byauth/grattan/peg.html.

V. Jenssen and Lorne Murdock, “Review of the Conservation of the Machault Ships timbers (1973-1981)”, Proceedings of the ICOM Committee for Conservation Working Group on Waterlogged Wood Conference, Ottawa, 1981, D.W. Grattan ed., J. C. McCawley ed. special discussions. (Ottawa: ICOM Waterlogged Wood Working Group, 1981)

 

Ship Name: Mallorytown Wreck

Location: Ottawa?

Date Sank: 1812?

Date Salvaged: 1967

Conservator:  Parks Canada

Background:  20% PEG 1000 then 12.5% PEG 1450  Poorly treated in the beginning?

Source:  http://cool-palimpsest.stanford.edu/byauth/grattan/peg.html.  David Grattan posting to the distlist

 

Ship Name: USS Cairo Gunboat

Location: Yazoo River near Vicksburg, Mississippi

Date Sank: 1862

Date Salvaged: 1960-64

Conservator:  eventually, National Parks Service (1977)

Background: Originally salvaged by an organization of local enthusiasts called “Operation Cairo.”  Decision was made to pull up the ship first, then decide on treatment and funding afterward.  Widely considered an archaeological disaster.  Yanked up in pieces, considerable theft, not treated for many years and largely destroyed. 

Source:  H. Thomas Mc Grath, Jr., “The Eventual Preservation and Stabilization of the USS Cairo”, The International Journal of Nautical Archaeology and Underwater Exploration (1981) 10, 2 pp. 79-94.

 

 

Ship Name: Dover Bronze-Age Boat

Location: English Channel, Dover, Kent, Southern England.  (Dover Museum)

Date Sank: 1300-1600BC

Date Salvaged: 1993

Conservator: Mary Rose Trust, Jacqui Watson

Background:  Removed from a freshwater silt by cutting into sections.  Treated with PEG for a year (have not found what % or mw) and then freeze-dried.  Minor distortion, but enough to cause difficulty with reconstruction.

Source:  http://www.abc.se/~m10354/uwa/wreck-br.htm

http://www.doverdc.co.uk/museum/bronze_age_boat.aspx

 

 

Ship Name: Brown’s Ferry vessel

Location: Black River in eastern South Carolina

Date Sank: 1735 to 1740

Date Salvaged: 1976

Conservator: Katherine Singley

Background:  Made of live oak, pine, and cypress.  PEG 1450 was to be used, heated to 60C, increased by 1% every two weeks up to 60%.  Two years projected, slow air drying in low humidity planned.  Intended to apply 30% solution of PEG 4000 after that.  Dried under a tensioned cradle system? Treatment began around 1982?

Source Singley, Katherine R. “The recovery and conservation of the Brown’s Ferry vessel” In book. Proceedings of the ICOM Waterlogged Wood Working Group conference: Ottawa, 15-18 September 1981. ICOM Waterlogged Wood Working Group (1982), pp. 57-60


PEG Bibliography Annotated

April 4, 2009

BIBLIOGRAPHY OF ARTICLES RELEVANT TO PEG TREATMENT OF BASKETRY

* = Articles Ellen Carrlee had a copy

++ = Articles Dana Senge had a copy

Others are noted from their abstracts

* Alderson, Samantha.  (2008) Posting to the American Institute for Conservation Objects Specialty Group discussion list 12/4/2008.

Ellen Carrlee’s notes: discussion of the changes to polyvinyl acetate resins of the AYA_ series, which are no longer the same ones trusted for many years made by Union Carbide.  Conservation Support Systems and Talas still sell some of these resins made by a different manufacturer with some different specifications.  Seems that Union Carbide stopped making them back around 2005?

++ Alonso-Olvera, Alejandra, Setsou Imazu, Demetrio Mendoza-Anaya, Andras Morgos and Ma. Teresa Tzompantzi-Reyes.  (2002) “The Lactitol® Conservation of Wet Polychrome Wooden Objects Found in a 15th Century Aztec Archaeological Site in Mexico.”  In ICOM Committee for Conservation, 13th Triennial Rio de Janeiro. Vol II. 2002. pp 712-717.

Dana Senge’s notes: Calculated moisture content—by drying samples in oven at 105º C for 48 hours.  Weighed samples before and after drying- weight difference as percentage of dry weight gave moisture content. Determined artifacts low to intermediate degradation.  Wanted to preserve chromatic surface of black and blue pigment.  PEG modifies surface—excluded from testing.  Tested sugar/alcohol, Lactitol® method.  With Lactitol® method- biological attack can be avoided at low concentrations during impregnation.  Lactitol 5-55% over 4 months- requires heat to reach 90% solubility.  Lactitol®- 4-O(b-D- galactopyranosyl)-D-glucitol

* Astrup, E.E. “A Medieval Log House in Oslo – Conservation of Waterlogged Softwoods with Polyethylene Glycol.”  (1994)  Proceedings of the 5th ICOM Group on Wet Organic Archaeological Materials Conference, Portland, Maine. 16- 2- August 1993. pp 41-50

Ellen Carrlee’s Notes: Wood was identified as pine (Pinus silvestris) and spruce (Picea abies).  For both highly degraded and less degraded softwoods, 50-55% PEG 4000 was most useful.  She heated at 60C adding 10% every 8 weeks.  She was getting 3-5 % shrinkage in the 50-55% range, but more above and below it.  Waterlogged wood is already somewhat swollen, however.  Results similar to Hoffmann’s 1990 article on softwoods.  Wood with fairly intact cell wall structure might suffer from shrinkage with low mw PEG alone, perhaps the hygroscopic PEG pulls the water out of tyhe small spaces the molecule cannot fir into?  Mentions that the two-step method is really intended for wood like oak that tends to have areas of both low and high degredation.

++ Barbour, R. J. (1983). The Hoko Alder:  A Wood Technological Approach to the Conservation of Waterlogged Archaeological Wood.  M.S. Thesis, University of Washington.

* Barbour, R.J. and L. Leney.  (1982) “Shrinkage and Collapse in Waterlogged Archaeological Wood: Contribution III Hoko River Series.”  In Proceedings of the ICOM Waterlogged Wood Working Group conference: Ottawa, 15-18 September 1981. pp. 209-225.

Ellen Carrlee’s notes: Shrinkage from capillary tension happens when the free water is pulled by evaporation from the void structure of the wood.  Shrinkage is also caused from desorption of bound water from the cell wall.  Article gives extensive info about which cells collapse in which direction.

* Baron, Maggie, Anne Wright.  (1990) “The Conservation of Waterlogged Basketry Fragments from the William Salthouse.”  AICCOM Bulletin Vol 16 No 3 1990.  pp.85-92.

Ellen Carrlee’s notes: Ship sank 1841 Port Phillip Bay Australia.  Excavated 1983. Willow, a diffuse porous hardwood, juvenile wood.  Separately tested PEG 300 up to 10% and PEG 3350 up to 20% for a month.  Seemed that high mw was more successful?  Wonder why they didn’t try a two-step method.

* Bernick, Kathryn. Hidden Dimensions. WARP Occasional Paper 11, UBC Press.  Vancouver: Canada.  1998

Ellen Carrlee’s Notes: Several useful articles, including Kaye & Cole-Hamilton, Bernick, and Johns mentioned in this bibliography.

* Bernick, Kathryn. “Stylistic Characteristics of Basketry from Coast Salish Area Wet Sites.” In Hidden Dimensions.  WARP Occasional paper 11, UBC Press.  Vancouver: CANADA.  1998

Ellen Carrlee’s Notes: Good resource for the things we ought to be noting in the Before Treatment condition reporting regarding the structure of the basketry.

++ Bernick, Kathryn. (1991) Wet Site Archaeology in the Lower Mainland Region of BC.

Dana Senge Notes: Excellent summary of sites, repositories, conservation and current condition of materials from wet sites in the BC.  Specifics have been added to Sites table.

*++  Bilz, Malcolm, Tara Grant and Gregory S. Young.  (1999) “Treating Waterlogged Basketry: A Study of Polyethylene Glycol Penetration Into the Inner Bark of Western Red Cedar.”  Proceedings of the 7th ICOM Working Group on Wet Organic Archaeological Materials Grenoble 1998.  pp.249-253

Ellen Carrlee’s notes: PEG 200 concentration over 20% but under 50% to give penetration to secondary wall without moist waxy surface.  Cobalt thiocyanate in ether gives blue stain when it bonds with PEG, and inhibits autofluorescence of lignin. This study was with FRESH cedar bark samples, presumably because that would remove the obstacle of trying to examine degraded plant structures.  Conclusions mention that archaeological samples need to be tested.  I’m bothered by a foggy memory of seeing somewhere that lignin might have decreased fluorescence when the wood is very deteriorated?

Dana Senge Notes: Examination of extent PEG 200 penetrates cell walls in fresh western red cedar inner bark in aqueous solutions up to 20- 50% by volume.  Cobalt thiocyanate in ether- when viewed in bright field—gives blue color only where PEG has been retained.  Examined transverse sections.  Test Results

20% PEG 200—dry and cupped due to shrinkage

30% PEG 200—dry, less cupped

40% PEG 200—moist, more flexible, flat

50% PEG 200—wax and moist

20% PEG 200 for 4 months and 20% PEG 200 for 12 months showed same level in impregnation

PEG 400-  didn’t penetrate very well

Actual PEG concentration in basket sample lower than concentration in soln/bath— so 50% PEG 200 in solution is lower in sample.  Freeze-drying above Eutectic can pose problems.  Reducing amount of water in system that would actually freeze in freeze drying and sublimate.  Higher then Eutectic would need to air dry. Examined 5% 3350- frozen and freeze-dried.  Did not penetrate cell wall- did fill lumina.  Cobalt thiocyanate stain caused 3350 to become liquid rather than crystalline

* Bilz, Malcolm, Lesley Dean, David W. Grattan, J. Clifford McCawley, and Leslie McMillen. (1994)  “A Study of the Thermal Breakdown of Polyethylene Glycol.”  Proceedings of the 5th ICOM Group on Wet Organic Archaeological Materials Conference.  Portland, Maine. 1993.  Ed Per Hoffmann.

Ellen Carrlee’s Notes: PEG from ten year old artifact did not decrease in molecular weight.  Keeping oxygen or air out slows PEG degradation.  Thermal aging increases PEG degradation.  Slightly more degradation of PEG 3350 in presence of iron salts, but not so much with PEG 200.  Less degradation of PEG 3350 in oak than by itself.  BHA (not very soluble in water) helps reduce oxidation degradation of PEG 3350; propyl gallate does not, and also forms colored complexes with iron.  No degradation of PEG with natural aging either in artifacts or by itself.  Impregnation should take place at room temperature to avoid degradation.  Store PEG at its most concentrated.  PEG is reasonably reversible and can be leached from artifacts.  Lower concentrations of PEG 400 (below 40%) oxidize more.  In degradation, are we getting smaller molecules, do they go into the wood, or do they evaporate?

*Bilz, Malcolm; David W Grattan, Judith A Logan, Charlotte L. Newton.  (1991) “An Investigation of Polyox for the Conservation of Wet Archaeological Textiles and Other Fragile Fibrous Materials.  In Proceedings of the 4th ICOM Group on Wet Organic Archaeological materials Conference Bremerhaven August 20-24, 1990.  Per Hoffmann, Editor. pp 189-208

Ellen Carrlee’s notes: POLYOX is a trade name for polyethylene oxides made by Union Carbide, ranging in MW from 100,000 to 8,000,000.  PEGs are a lower MW homolog of POLYOX.  They are stable and performed well in the testing, remain soluble in water, and give thin film consolidation to textiles without losing drape or becoming glossy.  It has a high degree of wet tack and may feel slightly tacky after the treatment is done if held between the fingers for a few seconds.  Application after freeze drying is better than before freeze drying.  Mixing above 1% concentrations results in a substance that is difficult to work with.

* Bjordal, Charlotte and Thomas Nilsson “Decomposition of Waterlogged Archaeological Wood.”  (2002) In Proceedings from the 8th ICOM Group on Wet OrganicArchaeological Materials Conference.  Stockholm, 11-15 June 2001. pp.235-247

Ellen Carrlee’s notes: From the abstract…objects in near-anaerobic environments are soft and spongy with low density and high water content, caused by wood degrading erosion bacteria.  Dimensions and surface details remain intact, since the bacteria can’t degrade all parts of wood cell wall.  But more deterioration can occur when wetland is drained, since white rot is then able to work on the final degredation.  Summary of methods to determine degree of degredation include measurements of density, measuring the maximum moisture content, chemical analysis to show decrease in cellulose content.  In waterlogged environments, erosion bacteria are the main cause no matter what the pH, soil, fresh or saltwater.  They are the only degraders active in anaerobic conditions.  The S3 layer next to the lumen is the first attacked, then the S2 which has the most cellulose, and they leave behind a dark granular substance.  Moderately degraded wood will show apparently sound tracheids next to heavily degraded cells.  Lignin rich frame of the middle lamellae is left behind.  Observation carried out with half polarized light, you may see a heterogenous pattern of totally degraded cells and sound ones making a black and white checked pattern.  In the discussion afterwards: the slime material mixed with lignin and secondary degraders make it look under the microscope like there is still secondary cell wall, but it does not exist.  Slime material does not wash out easily.  Judy Logan mentions during the discussion that PEG is a wonderful plasticizer and can get between almost anything including to swell epoxies.

* Boone, R.S. and E.M. Wengert. (1998)  “Guide for Using the Oven-Dry Method for Determining the Moisture Content of Wood.”  Forestry Facts University of Wisconsin Dept of Forestry Ecology and Management No 89 June 1998.

Ellen Carrlee’s notes: %MC = amount of water in the wood (that is, original weight minus the oven dry weight) divided by the oven dry weight of the wood times 100.  In oven drying, all of the water must be gone, but the wood must not be damaged.  For best results, must used minimum of 100grams.  From lumber, they should be 1” long along the grain and the full width of the thickness of the board.  Weighing to 0.05g is recommended.  Oven temperature empty should be 215-217F.  Above may char and below may not remove all the moisture.Heat samples 18-24 hours.  Method given for drying in a microwave oven with a rotating carousel to speed up the process : 200-360 watts (medium to low power) for up to 30 minutes for green wood.  10-12 minutes for dryer wood.  Then the oven only takes 2-8 hours to fully dry the samples.

Borden, Charles E.  (1976) “A Water-Saturated Site on the Southern Mainland Coast of British Columbia”  The Excavation of Water-Saturated Archaeological Sites.  National Museums of Canada.

Ellen Carrlee’s notes: Basketry 50% solution of PEG 1500 (Carbowax) for 21/2 to 4  months.  This is the Musqueam site, DhRt4 dated 2970 +/- 90 BP.

*++ Brown, C.E. “(1991) Conservation of Waterlogged Wood: A Review.” In Waterfront Archaeology: Proceedings of the 3rd International Conference on Waterfront Archaeology. Held in Bristol 23-26 September 1988.    pp 121-123

Dana Senge’s Notes: Sealed anaerobic deposits slow bacterial activity.  Softer more soluble cellulose content is always depleted to some extent leaving behind harder structural substance—lignin. Conservation is physically bulking out lignin framework with hard materials. Treatment of composites—with metal components.  PEG is acidic—aggressive towards metal.  Recent research includes use of corrosion inhibitors and alkaline PEG-like substance?  Summarizes Hoffman’s work (1981)—shorter molecular weights of PEG= good for treating lightly degraded woods, but too much has hygroscopic results.   Larger longer MW bulks up lumina – good for badly degraded wood.  Description of freeze-drying logic is very straightforward.  Vacuum serves to make water vapor pressure on ice surface lower than the saturation vapor pressure in the ice.  Latent heat source needed to replace energy lost by removal of water vapor.  Description comes from Rosenqvist, 1975.

++ Brown, Margaret Kimball..(1974)  “A Preservative Compound for Archaeological Material” in American Antiquity.  Vol 39, Issue 3 July 1974. pp 469-473.

Dana Senge’s notes: Referenced by Grosso in treatment of cherry bark ties. Ethulose and PEG and Fungicide (ester of paraoxibenzoic acid) Used as reversible surface preservative in the field—“better than Elmer’s” PEG 1000- used for stone, bone, shell and pottery. PEG 400-fabrics Prep:  Ethulose (3/4 ox) added to cold water gradually and stir.  Add 4 parts PEG to 1 part Ethulose—stir until dissolved.  PEG increased flexibility.  In the field began applying as soon as skeletal material was brushed off to minimize differential drying between exposed and unexposed bone.  Compound applied by spray or brush.  Four applications average—each coat applied before the previous totally dry.

*++ Brownstein, Dr Allen.  (1982) “The Chemistry of Polyethylene Glycol.”  Proceedings of the ICOM Waterlogged Wood Working Group Conference Ottawa 1981.   p.279-287.

Dana Senge’s notes: PEG has waxed and waned in use—people keep coming back to reexamine its use.  PEG is flexible polymer capable of random coiling with numerous folds and twists throughout the chain.  Compact molecules—end to end distance proportional to square root of molecular weight.  Solubility due to hydrogen bonding.  Higher molecular weights possess polyether character.  H-Bonding to ether oxygen  atoms create solvent shell as opposed to monolayer.  At T slightly above 100 degrees C-  PEG’s become insoluble in water (rupturing H-bonds involved in complexation.)  May conclude that size of complexation (between solvent and molecule would vary from solvent to solvent.  Studies shown binding cations greater in methanol than in aqueous soln.  PEG/Water complex larger due to greater numbers of bound water molecules.  PEG/t-butanol complex—smallest of the three—structure of t-butanol severely limits number of bound t-butanol molecules.  Complexing: with phenol, borax/boric acid?  association reactions between PEG and Boric/Borates not observed.  PEG- Phenol associations have been observed, similar to water.  Brownstein raised—clathrate complex formed between Urea and PEG—creates hard solid that melts at 133 degrees C.  Suggest that may strengthen degraded wood. Degradation of PEG- Fairly stable at acidic pH levels  Thermal degradations accelerated with extreme pH. Pearson and MLF (pg 280)  No one has studied long term effects of treating a soft degraded wood with PEG. Will hygroscopic nature of PEG attract moisture to wood?  Resulting breakdown over long term? Brownstein response:  Long Term degradation of PEG accelerated by heat, moisture content, air, possibly light certain decomposition products—corrosive toward badly degraded wood (formic acid) oxygen causes degradation. Decomposition can be detected by a darkening of color or by drop in solution viscosity and pH -degrades through random chain scission. -can use anti-oxidants to reduce degradation (0.05-0.10% concentration:  p-methoxyphenol or phenothiazine, or food grade BHA (Butylated Hydroxy Anisole), BHT (Butyalated Hydroxy Toluene) or propyl gallate?  want to minimize oxygen and UV exposure  (UV degrades Lignin)–Trace metal ions may accelerate the decomposition of PEG hydroperoxides—Ferrous, Ferric and Cupric salts  PEG does not support bacterial growth  Discussion of Pre Treatment—to improve impregnation—various opinions include use of EDTA and acid.

++Bugni, Simone et al. (2008) “Evaluation of Conservation Treatments for Archaeological Waterlogged Wooden Artefacts”  published online at http://www.ndt.net/article/art2008/papers/162Bugani.pdf, accessed in March 2009.

* Caple, Chris and Will Murray. (1994).  “Characterization of a Waterlogged Charred Wood and Development of a Conservation Treatment.”  Studies in Conservation. Vol. 39, No. 1 1994 pp 28-38.

Ellen Carrlee’s notes: PEG 4000 was used as a surface consolidant prior to lifting the “charcoal” some of which was waterlogged when excavated from a Neolithic site. Wood (oak) was thought to contain some of the original lignin.  Various PEG treatments and consolidation were tested, including the use of PEG 400, PEG 4000, glycerol, Butvar B-98, Klucel G, Paraloid B-72, and epoxy.  10% PEG 400 followed by slow air drying over 40 days gave a good result for waterlogged samples.  This left the char looking good but very fragile.  The consolidants tested did not give satisfactory results, and the authors felt the most promising direction was PEG 400 and PEG 4000 in high concentrations.

* Carrlee, Ellen.  (2005) “Conservation and Exhibit of an Archaeological Fish Trap.”  In American Institute for Conservation Object Specialty Group Postprints.  Vol. 13, 2005.  pp 117-129.

Ellen Carrlee’s notes: Montana Creek Fish Trap was excavated in 1989-1991 dated 400-600 years BP.  Made of spruce and hemlock wood elements and basketry-like spruce root lashings.  Treatment notes are incomplete but suggest the trap was impregnated unheated for several months with 10% PEG 200, 5% PEG 1000 and 10% Carbowax Compound 20M, which seemed to be a PEG-like substance with molecular weight of 15,000 to 20,000g/mol.  Due to its size, the trap was slowly air dried after impregnation.  Spruce root was rather brittle after impregnation, small wads of Japanese tissue with wheat starch paste and a small amount of Jade 403 PVA emulsion were used to gap fill and adhere the loose root elements.  Strips of Tyvek were adhered around the structure wooden elements in loose loops with Acryloid B-72.  Paper describes mountmaking as well.

++Chen, Yuansheng, Yulin Xie, (2000)  “A New Method for Treating Ancient Chinese Lacquer on Waterlogged Wood”. In Ostasiatische und Europäische Lacktechniken: internationale Tagung des Bayerischen Landesamtes für Denkmalpflege und des Deutschen Nationalkomitees von ICOMOS in Zusammenarbeit mit dem Tokyo National Research Institute of Cultural Properties, München, 11.-13. März 1999  pg 139-143.

* Clarke, Richard W. and Jane P. Squirrel. (1982)  “A Theoretical and Comparative Study of Conservation Methods for Large Waterlogged Wooden Objects.”  Proceedings of the ICOM Waterlogged Wood Working Group Conference Ottawa 1981. pp. 19-27

Ellen Carrlee’s notes: 5 methods considered: 1) Dehydration and consolidation, involving treatments like acetone/rosin, alcohol/ether/rosin, dammar resin, Tetraethoxysilane, and dehydration with solvents.  All of these aim to reduce the capillary tension issue of water leaving the wood and thus control shrinkage.  Specialist equipment and large volumes of solvent count against these methods.  2) Freeze-drying to avoid the water phase.  Pre-bulking probably needed, equipment for large items expensive.  3) resin impregnation and polymerization including methods with UV, gamma radiation, heat or catalysts.  Concerns about safety and expense. 4) PEG to bulk as the most common method.  Takes a long time but less expensive than many other methods. 5) Air drying, including slow drying in controlled humidities.  Some evidence this works for things in good condition, very cheap.

*++ Cooke, Vincent, Deborah Cooke, and David W. Grattan.  (1994) “Reversing Old PEG Treatments of Objects from the Ozette Site.”  Proceedings from the 5th ICOM Group on Wet Organic Archaeological Materials Conference, Portland, Maine 16-20 August. 1993. pp 92-109

Dana Senge’s notes: Artifacts retrieved were more recent origin ~ 500 BP.  55,000 artifacts, 1.5 million faunal remains.  Clay preserved these artifacts in anaerobic conditions. Not suffered fungal decay and little alteration of cell wall structure.  In 1990 concerns about condition of pieces led to re-assessment.  Describe collections as dark brown to black with layer of excess PEG on surface.  Artifacts stable.  540 may not be entirely effective against cell collapse- but did prevent shrinkage and provided preservation.  Some of the condition described above may be attributed to poor RH control and hygroscopic nature of PEG-  Makah CRC has new storage area with new climate controls.  Describe attempts to remove acetone rosin with acetone.  (Rosin was probably colaphany according to Grosso article—but removal attempts didn’t include ethanol???)  Basketry Fragment re-treatment (Small fragments (4×3 cm) A- removed/reduced PEG 540 in extraction bath of water with 0.1 sodium ortho phenyl phenate, Artifact became lighter in color. Frag freeze dried without PEG.  Results: brittle and easily broken, but weave pattern clearly revealed. Consolidated with parylene C… fungal hyphae were not cleaned from surface and trapped by parylene leaving white deposit on surface.  B- PEG extracted with 70% ethanol/water, Freeze dried (-20°C under vacuum)  brittle and easily broken, consolidated with Polyox.  Results:  Wave patterns more easily discerned after Treatment- color improved. Superior in appearance to A but less strength. C-PEG extracted with 70% ethanol in water, freeze dried.  No additional treatment  Results: excellent in appearance, but brittle.  4th fragment extracted PEG with 70% ethanol.  Cut into three separate sections.  1) freeze dried, 2) freeze dried, Polyox coat, 3) Freeze Dried, Paralyne C coated.  Results—visually preferred 2,  more realistic in texture and color.  No examination of structure on microscopic lever or with SEM.  Comments from discussion group on Cooke paper:  Barbara Purdy- has used 540 successfully in past, not seeing excess and hygroscopic effects observed with Ozette pieces. Purdy was part of Ozette site from beginning.    Grattan response—likely that location of museum is cause—light RH.. (however- Purdy works in Florida…high RH!)  Some comments on experience with TEOS (Tera ethyl ortho silicate) none successful

Ellen Carrlee’s notes: Treated with PEG 540 blend c. 1973, hygroscopic, dark, heat used.  Extracted PEG, retreated with 2-step PEG 200 at 15% for 40 days, and PEG 3350 at 9.5% for 20 days, then freeze dried.  Acetone Rosin was found irreversible.  They also consolidated with Polyox 2.5%.  Discussion at end is very good…Grattan thought darkness of Ozette treatment was due to bulk treatment contaminants.  Also, some hardwoods couldn’t take the osmotic effect of starting out with 50% PEG 540 blend and it caused some collapse.  All agreed TEOS worked poorly.

* Cook, Clifford and David Grattan.  (1991)“A Method of Calculating the Concentration of PEG for waterlogged Wood.”  Proceedings of the 4th ICOM Group on Wet Organic Archaeological Materials.  Bremerhaven 1990.

Ellen Carrlee’s notes: Liquid grade, such as PEG 200 is used to control cell wall shrinkage and waxy solid PEG 3350 is used to give some structural strength to the wood.  Important to know:

Wood species

Actual density of the wood

The normal density of undeteriorated wood

The Moisture content at the fiber saturation point of the undeteriorated wood.

These are the parameters used by PEGCON.  Lower MW PEG such as PEG 200-600 penetrate into the cell wall better than higher MW.  Higher MW PEG is meant to fill in the lumens and has been shown to work better on very deteriorated wood.  Too much PEG 400 results in weeping , soft, humidity-sensitive wood.

Too much PEG 3350 results in heavy wood, harder to dry. Umax is the maximum moisture content, increases with deterioration.  Some woods have a higher Umax naturally than others, so that’s why you have to know the species.  Over 55% PEG mixture might not freeze in the drying process.

* Christensen, B. Brorson. (1970)   The Conservation of Waterlogged Wood in the National Museum of Denmark. National Museum of Denmark, Copenhagen.

Ellen Carrlee’s notes: Includes history of treatments 1859-1962, and reports on work thusfar on Viking ships from Roskilde Fjord.   Includes PEG 4000 in various solvents but having difficulty with the issue of oak penetration.  Methylene chloride is the best solvent for removing PEG after treatment.  Water is too slow and results in too much rubbing which obscures fine details and rounds sharp edges.  Cold treatment with PEG 4000 as opposed to warm treatment resulted in less collapse of the oak.  Began with 25% and increased to 50% for a year total

++Croes, Dale. R, John Fagan and Maureen N. Zehendner (ed). (2007) Testing the National Historic Landmark Wet Site 35MU4, The Sunken Village Archaeological Site, Multnomah County Oregon. Online publication: http://www.library.spscc.ctc.edu/electronicreserve/anth280/SunkenVillage/SVFieldReport2006.pdf, accessed: March 2009.

Dana Senge’s notes: Radiocarbon dates of site range from 130-600 years BP (1400-1870)

++Croes, Dale. R, John Fagan and Maureen N. Zehendner (ed). (2008). A U.S. “National Historic Landmark” wet site, The Sunken Village Site (35MU4), Portland, OR- The First Explorations. Synthsized 2006-2007 Field Season Report. Online publication: http://www.library.spscc.ctc.edu/electronicreserve/anth280/SunkenVillage/SVSynthesizedReport2007.pdf, accessed: March 2009.

Dana Senge’s notes: Discusses Lab methods: materials washed, tagged with metal ring tags (stainless steel specified in email communication with Dale Croes 3/22).  Artifacts sewn into plastic screen/mesh bags, treated in 50/50 soln of water and PEG 400 for 4 months. Pgs 76/77

++Croes, Dale R, Rhonda Foster et al. (2005) Qwu?gwes – a Squaxin Island tribal heritage wet side, Puget Sound, USA. In Archaeology from the Wetlands: Recent Perspectives.  In Proceedings of the 11th WARP Conference, Edinburgh 2005, ed. John Barber, Dr. Ciara Clark et al.  WARP Occasional Paper 18.  pg 135

++ Croes, D.R. (2001) North Coast Prehistory–Reflections from Northwest Coast Wet Site Research.” in, Jerome S. Cybulski, ed., Perspectives on Northern Northwest Coast Prehistory, Canadian Museum of Civilization, Hull, Quebec. Mercury Series Paper 60. 2001,

Dana Senge’s Notes: Summary of styles of baskets and materials found in PNW wet sites.

Croes, Dale R.  (1976) “An Early Wet Site at the Mouth of the Hoko River”  The Excavation of Water-Saturated Archaeological Sites. National Museums of Canada.  1976 pp.201-232

Ellen Carrlee’s notes: Initial excavation in 1967, artifacts treated with 50% solution of white glue.  Summer 1973 excavations preserve at Ozette Project’s Neah Bay lab with Carbowax 1500 PEG, the same method applied to Ozette artifacts.  Hoko is 45CA213.  Dated 2210 +/- 70 and 2750 +/

++ Croes, Dale R. (1976) “The Excavation of Water-Saturated Archaeological Sites (Wet Sites) on the Northwest Coast of North America.”  National Museum of Man Mercury Series, Archaeological Survey of Canada.  Paper 50.  National Museums of Canada, Ottawa.  1976.

Ellen Carrlee’s Notes: I have not yet seen this volume.  Kathryn Bernick tells me that at the conference each presenter answered several questions, one of them about conservation treatments.  All the papers are preliminary data and some details changed with further analysis.  For about half the sites in this volume, Bernick says there has been no further analysis and reporting, and for most of the others it was only selected parts of the assemblages.  Of the sites in the volume, comprehensive final site reports only exists for Hoko and Little Qualicum.  Personal communication with Bernick, March 24, 2009.

Dana Senge: has taken extensive notes from this volume and compiled info into table of PNW sites, dates, treatments with condition notes as she is able to examine these collections.

++ Daugherty, Richard and Dale Croes. (1977?) “Wet Sites in the Pacific Northwest.” In Pacific Northwest Wet Site Wood Conservation Conference, September 19-22 1976 vol 1 pg 17.

Dana Senge’s notes: Discusses excavation technique developed using water spray from hoses to removed strata layer by layer. Mentions- Fishtown:  a lot of sewage had been dumped into Skagit river, these artifacts were rich in organic materials which started to grow in lab before treatment.  Musqueam- 3000 years old, treated fish nets (gill net). Hoko- Alternating clay and organic material layers.  Ozette- 1967: first few basketry fragments were soaked in Elmer’s  (produced stiff whitish looking basket)  Understands that Elmer’s formula has changed and even more unsuitable than before.  Also attempted field/excavation stabilization by brushing PEG onto objects

DeJong, J. (1978) “The Conservation of Shipwrecks.”  ICOM Committee for Conservation 5th Triennial Meeting Zagreb 1978.  78/7/1.

* DeWitte, Eddy, Alfred Terfve, Jozef Vynckier.  (1984) “The Consolidation of the Waterlogged Wood from the Gallo-Roman Boats of Pommeroeul.”  Studies in Conservation Vol 20 no 2 1984.  pp 77-83

Ellen Carrlee’s notes: PEG impregnation with PEG 4000 up to 85% heated to 65C in a steel tank.  Oak with no solid core.

* Endo, Rie, Kaeko Kamei, Ikuho Iida, Yutaka Kawahara.  (2008) “Dimensional Stability of Waterlogged Wood Treated with Hydrolyzed Feather Keratin.”  Journal of Archaeological Science 35, 2008 pp 1240-1246.

Ellen Carrlee’s notes: Feathers have lower MW and cystine content than wool or other hair keratins.  Waterlogged wood (oriental elm) with Umax 480% was treated with duck feather keratin and had a anti-shrink efficiency of 90 at the final concentration of no less than 30%.  Generally the treatment does not go above 40% concentration.  Duck feathers worked better than chicken or goose.  Sttributed to higher crystalline index and stronger “anti-alkali” structures.  Also effective with elm, oak, camphor, and magnolia.  Mentions research by Kohdzuma et al 1996 that says Umax of waterlogged hardwood is higher than softwood and therefore treatment is more difficult.  They used 10g feathers in 90mL of 1N sodium hydroxide to dissolve the feathers at 70C for 3 hours, then neutralized it with acetic acid.  The sampels were immersed at 60C up to 40% with concentration raised every 3 days.  Specimens were dried at ambient temp.

*Erling, Jo Ann.  (1991) “Report: The Conservation of Artifacts from the Glenrose Cannery Site DgRr6.  Archaeology and Outdoor research Branch.  Ministry of Municipal Affairs, Recreation and Culture Province of British Columbia.  March 1991 Unpublished.

Ellen Carrlee’s notes: The material is approximately 3500-4000 years BP and the cellular structure in the material was quite degraded, especially the basketry.  PEG used was “ Carbowax 540 formerly Carbowax 1500” at 10-20% for six months, then freeze-dried for 5 days.  This is described as the same treatment used on the artifacts from the Beachgrove Water Hazard Site DgRs30.  For the Glenrose Cannery Basketry, an additional application or two of Rhoplex 33 was brushed on the surface in an effort to further stabilize them.  It seems that descriptions of additional consolidation in the literature are often indicative of undertreatment with PEG.  The report describes soaking objects (like wooden stakes) for extended periods to increase penetration, but I think the problem may have been not using high enough MW of PEG.

* Florian, Mary-Lou; Dale Paul Kronkright and Ruth E. Norton, (1990) The Conservation of Artifacts Made from Plant Materials. J. Paul Getty Trust.

Ellen Carrlee’s notes: Florian p.67: Western Red Cedar bark is secondary phloem tissue, takes place of true bark.  Made of sheets of strong fibers.  Includes sieve cells, parenchyma cells and phloem fibers (mechanical strength.)  Pits are exaggerated when deteriorated.

*++ Florian, Mary-Lou and Richard Renshaw-Beauchamp. (1982) “Anomalous Wood Structure: A Reason for Failure of PEG in Freeze-Drying Treatments of Some Waterlogged Wood from the Ozette Site.”  Proceedings of the ICOM Waterlogged Wood Working Group Conference Ottawa 1981 pp. 85-98

Dana Senge’s notes: Done at request of Milfie Howell, conservator at Neah Bay in 1979. Tested on non artifact wood samples from Ozette to determine if these treatments could be used for artifacts of comparable material.  Standard PEG treatment had not been successful on a few small artifacts and thought freeze drying might be a good alternative… possibly help predict results  PEG 540 Blend 50% for 6-8 months. Freeze drying and PEG Freeze drying treatments overcame majority dimensional changes-  but not surface cracks.  PEG/FD did eliminate more cracks than FD alone.  Most important observation: inherent dimensional instability due to anomalous growth could not be overcome by treatment.

Ellen Carrlee’s notes: Factors that decrease the penetration of the PEG include:

Few and small hardwood cells

Inclusions (gum and tyloses) in hardwood vessels

Abundant hardwood thick walled fiber cells

Short soft wood longitudinal tracheids

Absence of ray tracheids

Absence of radial and longitudinal resin canals

Aspirated and encrusted bordered pits

Blind simple pits

High specific gravity

Ray parenchyma containing resin or extraneous material

Reduced tangential wall pitting

Extractives in heartwood

Picea sp. (spruces) and Thuja pliacata (Western red cedar) have no tangential permeability due to little tangential wall pitting, blind pits, and resin in the ray parenchyma cells.  Spruce more permeable than red cedar due to resin canals and ray tracheids.  Cedar is vulnerable to collapse of radial walls of the tracheids.  In some woods, large thin-walled early wood tracheids adjacent to thick walled later wood tracheids can collapse and cause uneven grain appearance.  In this case, spruce showed this result.  Roots have many parenchyma cells and can have excessive longitudinal shrinkage.  List of history-chemical tests given.  Many softwoods samples show open enlarged tracheid bordered pits which make the wood abnormally porous.

Florian, Mary-Lou E.  (1982) “Analyses of Different States of Deterioration of Terrestrial Waterlogged Wood –  Conservation Implication of the Analyses.” Proceedings from the ICOM-CC Sixth Triennial Meeting Ottawa 1981.

Ellen Carrlee’s notes: Chemically altered lignin has increased solubility, prolonged PEG treatment might solubilize the lignin esp if the PEG is depolymerized.  Bacteria attack softwood tracheids.  Bordered pits show it.  Variability of waterlogged wood is due to combination of: different states of deterioration, different species characteristics, different physical description of the artifact, and history of artifact prior to burial.  Unlike cellulose, lignin is very persistent and can exist in normal amount in very very old wood.  Lignin is the precursor of coal and oil (Breger 1952.)  Lignin is soluble in alkaline solutions.  (I guess it is good that PEG is a little bit acidic!)  Brown rot fungi alter lignin to increase its alkaline solubility but soft rot fungi do not.  Brown rot fungi selectively digest cellulose.  White rot fungi selectively digest lignin.  Good descriptions of microscopic appearance of these kinds of degradation.

* Florian, Mary-Lou. (1977)  “Waterlogged Artifacts: the Nature of the Materials.  Journal of the Canadian Conservation Institute.

Ellen Carrlee’s notes: In softwoods, most of the cells are tracheids, in hardwoods they are vessels and wood fibers.  Bark of western red cedar is actually the dead outer phloem.  Fibers have very thick walls.  High lignin and tannin content, so survives when sieve cells and parenchyma cells destroyed.  Very detailed description of the cells in cedar bark that is used for basketry.

Friedman, Janet P.  (1978) Wood Identification by Microscopic Examination: A Guide for the Archaeologist on the Northwest Coast of North America.  B.C. Provincial Museum, Heritage Record 5, Victoria B.C.  1978.

Ellen Carrlee’s Notes: I have not read this yet.  Kathryn Bernick tells me it is based on the methods Friedman developed to identify species of wood artifact from Ozette.  Wood only, not basketry, cordage, or bark.  Only source that Bernick is aware of that deals with shrub wood.  Personal communication with Bernick, March 24, 2009.

Giulminot, E., F. Dalard, C. Degigmy. (2000) “Electrochemical study of iron corrosion in various concentrations of polyethylene glycol (PEG 400) solutions”. Eur. Fed. Corros. Publ. 28, 2000  pp300-309.

Glastrup, Jens, Yvonne Sashoua; Helge Egsgaard, Martin Nordvig Mortensen.  (2006)  “Formic and Acetic Acids in Archaeological Wood.  A Comparison Between the Vasa Warship, the Bremen Cog, The Oberlander Boat and the Danish Viking Ships.”  Holzforschung.  Vol 60 No 3.  2006.

Ellen Carrlee’s Notes: Solid-phase micro extraction (SPME) and gas chromatography-mass spectroscopy (GC-MS.)  Content of formic acid relates to the content of PEG in the wood.  Formic acid may be partly related to the PEG.  Acetic acid is less in PEG treated wood than fresh wood.  Acetic acid probably comes from the wood, and is age-dependent.  Lowest in the 1000-year old wood tested.

* Grant, Tara and Malcolm Bilz.  (1997)  “Conservation of Waterlogged Cedar Basketry and Cordage.”  Proceedings of the 6th ICOM Group on Wet Organic Archaeological Materials York, 1996.

Ellen Carrlee’s notes: Parylene coating on cedar “bark” baskets from Scowlitz site (500-1200 years old)  treated with modified PEG treatment. 20% PEG 400 for 3 months and then freeze-dried.  Came out still too fragile.  Parylene is irreversible but worked well.  Need a special vacuum pyrolysis chamber to apply it.  NOTE: Bilz reported at the 11th ICOM-CC Triennial in Edinburgh Sept. 1996  that further study of Parylene shows that it does not age as well as they thought and it is not recommended for long term conservation.  Also, personal communication with Kathryn Bernick (April 9, 2009) she mentions that the Scowlitz baskets are all made of cedar withes (wood splints) and not bark.  Some of the cordage was indeed bark.

Grattan, David, Malcolm Bilz, Tara Grant and Judith Logan. (2006)   “Outcome Determines Treatment: an Approach to the Treatment of Waterlogged Wood”  Journal of Wetland Archaeology Vol 6 2006. pp.49-63.

Ellen Carrlee’s notes: describes methods used at CCI to determine and evaluate a treatment regime.

* Grattan, David.  Cons Dist List posting 30 Aug 2000

Ellen Carrlee’s notes: Mallorytown wreck treated in 1967 with 20% PEG 1000 and 12.5% PEG 1450 by Parks Canada.  Bremen Cog hull treated by Per Hoffman two-step PEG method now in Bremerhaven.  If excess PEG is not used and the RH is kept below 60% treated artifacts do fine.  Unstable sulphides in wood can oxidize to sulphates and eventually sulfuric acid, leading to destruction of the wood.  PEG ages more slowly in wood than by itself.  Lignin may act as anti-oxidant.  PEG is chemically unlikely to cross link with the constituents of the wood.

* Grattan, D.W. and R.W. Clarke.  (1987) “Conservation of Waterlogged Wood.”  In, Conservation of Marine Archaeological Objects. Ed Colin Pearson.  Butterworth. London and Boston. 164-206

Ellen Carrlee’s Notes: This is really the most comprehensive description of PEG use and especially its history, but of course it ends in 1987 AND this book is out of print and can be hard to come by. Unger, Schniewind, and Unger is also a good compilation and goes up to the year 2000. If PEG 3350 is too bulky to penetrate the cell wall, osmotic pressure could build and cause collapse.  Microcapillaries in the cell wall thought to be around 10nm in deteriorated wood. Idea that bulking the cell wall without bulking the lumina has better results: less PEG oozes out, more natural appearance.  Freeze drying gives a more even distribution of PEG.  Grades of PEG over 600 need to be warmed in order to be completely dissolved, and the complete solubility of PEG in water is very important.  Beginning impregnation with a low percentage of PEG is important to prevent osmotic collapse.  Up to 30% PEG 400 is needed to bulk the cell wall.  Freeze drying helps to keep it in there.  Very deteriorated wood doesn’t have much cell wall and so the low mw PEG can’t stay in there as well.  At the eutectic, PEG can’t freeze so you have a drying from with solid on one side and a mushy PEG solution on the other side.

*Grattan, David W.(1986) “International Comparative Study; Report”  .  ICOM Committee For Conservation Working Group on Wet Organic Archaeological Materials Newsletter. no 14. Feb 1986.

Ellen Carrlee’s Notes: I don’t remember seeing this published as a final thing elsewhere?  Grattan described his work at CCI.  He treated some samples with equal parts PEG 400 and PEG 3350 raised in 10% increments up to 30% v/v.  Frozen at -40C and then freeze dried at -20C.  results were good, but the very deteriorated samples should have had less 400 more 3350.   Second batch placed in PEG 3350 in sequential batches of 10%, 20%, 30%m 40%, and 50% v/v and then freeze dried.  Grattan feels the PEG reach the eutectic and did not freeze, so unfrozen PEG exuded onto the surfaces during freeze drying and some surface collapse.

*Grattan, David W.   (1986) “Some Observations on the Conservation of Waterlogged Wooden Shipwrecks.”  AICCM Vol. 12 No 3 and 4. 1986.

Ellen Carrlee’s Notes: Diagram of meniscus for water in a capillary, discussion of capillary tension induced collapse.  Issue of PEG penetration into white oak timbers.  Air pockets might prevent penetration.  For more deteriorated wood, concentrations over 50% are better, and fill the lumens in addition to bulking the cell wall.  Less deteriorated wood does all right with 10-30% which only bulks the cell wall.  Capillary action during drying concentrates PEG at the surface and depletes the core…this can be overcome using concentration over 50%. (ellen: also, if you freeze, doesn’t ice crystal formation influence where the PEG ends up?)  For humidity about 80% all PEGs are affected.  Lower concentrations of PEG can be used with freeze drying than with air drying.

* Grattan, David W.(1982)  “A Practical Comparative Study of Several Treatments for Waterlogged Wood”  Studies in Conservation Vol 27 No 3 Aug 1982 pp 124-136

Ellen Carrlee’s notes: Water content is a rough guide to the state of deterioration.  For smaller sample, no advantage to heating the PEG 400.  Didn’t help with penetration, shrinkage or cracking, but it did make end result darker.  In larger objects, heat may speed up the diffusion.  PEG 400 can end up soapy and attract dust.  Can melt some PEG 4000 on surface to make it stronger and less absorbent.  PEG 540 is a 50/50 blend og 300 and 1540 MW ave of 500-600…tends to creep out of the wood, looks heavy, dark, waxy.  Can be introduced unheated and unstirred in 10% increments over 18months.  Final concentration 64% v/v.

* Grattan, David.  (1982) “A Practical Comparative Study of Treatments for Waterlogged Wood part II The Effect of Humidity on Waterlogged Wood.”  Proceedings of the ICOM Waterlogged Wood Working Group Conference Ottawa 1981. pp. 243-252.

Ellen Carrlee’s notes: Wood treated with low MW PEG (400 or 540 blend) should not be exposed to RH above 60%.  Below that shouldn’t matter.

* Grattan, David W. (1980)  “ Consolidants for Degraded and Damaged Wood” in Proceedings of the Furniture and Wooden Objects Symposium: 2-3 July 1980.  Ottawa, Ontario. Pp. 27- 42

Ellen Carrlee’s notes: CCI testing of resins for consolidation of dry and degraded wood (not PEG treated) : Acryloid B 66, 67, 72, 82; Elvacite 2013, 2044, 2045, and 2046; Polyvinyl acetates AYAA, AYAC, and AYAF; polyvinyl butyrals butvar B72, 76, 98; Union Carbide’s XYHL, and Mowital B30H, B60H, soluble nylon, and Xylamon.  One of the better description of cautions for in situ polymerization: Vacuum chamber limits size and is expensive, heat is generated, time for impregnation is limited, monomer tends to drip out, wood may contain quinines or phenols that can impede the path of polymerization.  Problems with epoxy: no short term reversibility, first application determines final extent of penetration, mistakes are final, heat up top 75C is generated, poor appearance (dark). Both insitu polymerization and epoxy have an inherent lack of control.  Grattan provides a nice list of desirable characteristics: good adhesive, strength to surface and/or structure, flexible but hard, not creep, high concentration with low viscosity, simple application, non toxic, not yellow, short term reversibility, maintain mechanical properties.  He lists AYAA, AYAF and AYAC as having unsatisfactory Tg and therefore risking creep.  PVB’s have very good combo of high tensile strength, hardness and elongation of break.  Butvar B-98 has a lower viscosity than many PVBs.  Acrylics generally have the lowest viscosity.  PVBs may chalk on drying if applied in pure ethanol, esp if it has traces of water.  5% t-butanol to the solvent helps avoid it.  His frist choice was polyvinyl butyrals, then acryloids B72 and B67 and third AYAC and soluble nylon.

++ Grosso, Gerald (1978) “After Excavation, Then What” in Society for California Archaeology Occasional Papers in Method and Theory in California Archaeology.  1978.  Pg 53-56

Dana Senge’s notes: Discusses the need for conservation considerations even at dry sites.  No cookbook method can be applied.  Consider variations of environments from which something was removed and where it will be placed.  Practice of conservation: Continuing in experimental character and admission that we don’t have all the answers.

++ Grosso, Gerald. (1975?) “Field Conservation of a Variety of Waterlogged Artifacts from a Remote Archaeological Site” in Conservation in Archaeology and the Applied Arts: preprints of the contributions to the Stockholm Congress, 2-6 June 1975.  pg 250-253

Dana Senge’s Notes: Studied Seborg and Inveratity publications.  Science article (see below)  Conservation of 200 Year Old Waterlogged Boat with Polyethylene Glycol:Studies in Conservation 7 (1962) 111-119  The conservation of Wood from Fresh Water and Treating Wood with PEG. (Both from Diving into the Past, proceedings of a conference on Underwater archaeology. Minnesota Historical Society 1963.  Experimented (haven’t found full details yet)  Artifacts from vegetable origin were treated with 50% PEG Carbowax 1500 (later known as 540).  Water treated with Cytox 2013 biocide (100 ppm)  Treated 95% of 18,000 artifacts this way  5% wouldn’t accept PEG treatment—oil impregnated hardwoods?

++ Grosso, Gerald. (1976) “Volume Processing of Waterlogged Wood at a Remote Archaeological Site: Modification of old Techniques, Identification of Special Problems and Hopes for Their Solution”.   In Pacific Northwest Wet Site Wood Conservation Conference, September 19-22. 1976 volume 1  Neah Bay. WA.

Dana Senge’s Notes: Summary of site location and challenges of field conservation. Started testing after 1967 season: inspiried by Barkman (Wasa) Seborg and Inverarity. Samples of Various grades of PEG from Union Carbide. Tested on waterlogged wood. Build Field Lab for initial processing.  Lab at Neah Bay opened in 1971. Tested three types of PEG Carbowax 600, 1000, 1500 (name change reported in July 1976 paper—1500 became 540 and 1540 became 1500. Tests on waterlogged wood- piece divided into four parts.  Test samples were placed into test PEG Baths: 30% 600 in H2O, 30% 1000 in H2O, 30% 1500 (540) in H2O, 4th sample was allowed to air dry. After 60 days each sample had sunk to bottom of test tank.  These were allowed to dwell for an additional 30 days to increase impregnation. Mentions further tests made in 1970 on cedar bark basketry and other fragments.  Tests included: Application by hand of various grade. Variables included: solvents, concentration of PEG, temperature and times. Solvents: H2O, EtOH, MeOH, Isopropanol. Concentrations: 10-50% graduation, direct immersion into 50%, direct immersion into 100%.  Temperature ranged from ambient T (45-65°F) to 140° F  Times-  from topical application once a day for 5 days to continued soaking for 60 days. Considering results compared with cost, safety, efficacy and labor- developed a standard technique of 50% 540 in water for 30 days at ambient T. This stabilizes basketry, cordage, matting and solid wood artifacts up to an inch thick (cross section).  Thicker requires increased immersion time. Artifacts stored in unheated building with RH fluctuations 40-85% Observed ‘hygroscopic nature of PEG’  (possibly observed seeping/weeping)? Problems: Some artifacts resistant to PEG Treatment. After many tests: concludes some things will be preserved with little regard to concentration.  While some things are unstable regardless of adjusting any variable (concentration, time, temp of PEG treatment).  These artifacts appeared to be mostly hardwoods, most common feature: impreg with oil (hand, seal or food oils)  Possibly crosslinking of oils making difficult to remove and then PEG treat. Attempted several treatment solutions included HCL soak pre-PEG. Refers to Bertrand (ship with tools brought up from river. Alternative Treatments— Acetone Rosin Impregnation discussed by McKerrel, Roger and Varsnyi. Found difficult to get rosin. Appears to have treated with PEG first, then allowed to dry, then acetone rosin impregnation? Ethulose/PEG treatment: for wild Cherry Bark bindings (didn’t stabilize with PEG, tended to shrink around object until breakage occurred)  20% Ethulose 100 in 1000ml of water, stirring 30 min then adding 100g PEG, stirring until dissolved.  Also used for assembling Shattered artifacts-  solutions applied by medicine dropper or hypodermic needle and syringe.  Found that this mixture with PEG 4000 works best with basketry containing split limb elements.  Mixture using 540 blend more suited for bark elements.

*Halfors, Birgitta.  (1994) “Improvements of the Conservation Programme for Tank Treatment with Polyethylene Glycol at the Vasa Conservation Laboratory.”  Proceedings of the Fifth ICOM Group on Wet Organic Archaeological Materials, Portland, Maine 16-20 August 1993.  pp51-62

Ellen Carrlee’s notes: Tank treatments of the wooden Vasa material began in 1962.  Early approach used increased increments at the end, but the later treatments used larger increments at the beginning and smaller ones towards the end.  I had trouble making sense out of the abstract, have not yet reviewed the article

* Hamilton, Donny L. (1998) Methods of Conserving Archaeological Material from Underwater Sites.  Nautical Archaeology Program Department of Anthropology Texas A&M University.

Ellen Carrlee’s notes: Amount of water in waterlogged wood is calculated: weight of wet wood minus weight of oven dried wood divided by weight of the oven dried wood and multiplied by 100 to give % water.  Anything over 200% is considered degraded.  Explanations of other treatments for waterlogged wood are also given.

Hawley, Janet K. (1989) “Conservation of Waterlogged Rope from a 16th C. Basque Whaling Ship”  Conservation of Wet Wood and Metal, ICOM-CC Working Group on Wet Organic Archaeological Material and Metals  Fremantle 1987

Ellen Carrlee’s notes: Ship sank in 1565, Three most successful treatments, first one used most extensively:

1% Ethulose 400, 5% PEG 400, 2% glycerol in water

2% Ethulose 400, 10% PEG 400 and 2% glycerol in water

22% polyvinyl acetate emulsion, 10% PEG 400 in water

Hoffmann, Per, Adya Singh, Yoon Soo Kim, Seung Gon Wi, Ik-Joo Kim, Uwe Schmitt.  (2004) “The Bremen Cog of 1380: An Electron Microscopic Study of it Degraded Wood Before and After Stabilization.”  In Holzforschung Vol 58 No 3 2004 pp 211-218

Ellen Carrlee’s notes: Two-step PEG treatment for wood degraded primarily by erosion bacteria.  SEM/TEM investigation.  In degraded tissues, all cell types were filled with PEG 3000.   Non-degraded tissues are impermeable to PEG 3000 and impregnated only with PEG 200.  Confirms that PEG 200 goes into the cell walls.

Hoffmann, Per.  (2003?) “The Bremen Cog Project: the Conservation of a Big Medieval Ship” In ICOM-CC 13 Triennial Meeting Rio De Janiero 22-27 Sept 2002.  pp718-723

Ellen Carrlee’s Notes: Ship treatment took 19 years, was rebuilt before the PEG treatment.  Two-step treatment on a large scale.

Hoffmann, Per.  (2002) “The Conservation of the Bremen Cog: the Final Years”  Proceedings of the 8th ICOM Group on Wet Organic Archaeological Materials.  Stockholm 11-15 June 2001. pp 27-48

Hoffmann, Per.  (1997) “The Conservation of the Bremen Cog: Between the Steps.”  Proceedings of the 6th ICOM group on Wet Organic Archaeological Materials.  York 9-13 Sept. 1996. pp 527-543.

Ellen Carrlee’s notes: PEG 200 and then PEG 3000 as a two-step process.  First impregnation of PEG 200 took 10 years due to funding.  Can reduce the amount of PEG you need by putting salt water filled displacement units all around the boat in the tank.  63% PEG 3000 was used.  At publication, there were still 2-3 years projects for the second step to be completed.

++Hoffmann, Per. (1993) “Restoring Deformed Fine Medieval Turned Woodware”. In ICOM Committee for Conservation tenth triennial meeting, Washington, DC, 22-27 August 1993: preprints. pp 257-261.

Dana Senge’s Notes: Retreatment of dried misshapen wooden artifacts with PEG.

* Hoffman, Per.  “On the Stabilization of Waterlogged Softwoods with Polyethylene Glycol (PEG).  Four species from China and Korea.”  Holzforschung. Vol. 44 No 2.  1990.  pp 87-93.

Ellen Carrlee’s notes: Best stabilization of degraded softwoods is 50% PEG4000 with cross section shrinkage of only 2-4%.  Chinese Red Pine Pinus massoniana, Pinus densiflora, Chinese Fir Cunninghamia lanceolata, and Cryptomeria japonica treated with PEG 400 and PEG 4000.  All species responded the same.  Best stabilizations with 20% PEG 400 and 50% PEG 4000.  Using higher concentrations for softwoods is not effective. PEG 4000 cannot penetrate cell wall but can extract water from it.  PEG contracts 7% on setting.  Vasa used molten PEG 6000 on the surface, but it is a hard and shiny lacquer.

* Hoffmann, Per. (1986) “On the Stabilization of Waterlogged Oakwood with PEG II Designing a Two-Step Treatment for Multi-Quality Timbers.”  Studies in Conservation 31, 1986 pp.103-113

Ellen Carrlee’s notes: Bremen Cog PEG 200 and then PEG 3000.  Two step for thicker woods with outer layer of degraded wood and a core of less degraded wood like oak and pine.  Can even do simple air drying afterwards.  Results with intermediate MW not as good as two step.  PEG 200 stabilizes slightly degraded wood better than PEG 300.  Maybe some lower MW PEG diffuses out during the second step, but some is trapped or adsorbed in the capillaries.  Doesn’t weep until RH is 86%.  Can be air dried, too big for a freeze dryer.

* Hoffmann, Per. (1985) “On the Stabilization of Waterlogged Oak with PEG – Molecular Size Versus Degree of Degradation.”  Waterlogged Wood Study and Conservation, Proceedings of the 2nd ICOM Waterlogged Wood Working Group Conference, Grenoble, France.  28-31 August? 1984.  pp. 243-252.

Ellen Carrlee’s notes: More degraded oak does better with PEG 3350, while less degraded does better with PEG 200.  PEG 1450 is poorer for both.  A 2-step method is more effective.  For a long time people were afraid to use anything under PEG 1500 for fear it would be too hygroscopic.

++ Hoyle, Robert J. (1977?) “Relating Wood Science and Technology to the Conservator” In Pacific Northwest Wet Site Wood Conservation Conference, September 19-22 1976 vol 2 pp 99.

Dana Senge’s notes: Driest atmospheres—in equilibrium with wood about 5% moisture content. Indoor environments rarely produce moisture contents above 10-12% Shrinkage observed from fully saturated to dry 3.5-10% dependent upon species.  Western red cedar on low end of scale.  Artifacts from waterlogged sites in swollen condition- larger than they wood be in use (5-10% larger than in use).  When we preserve with PEG we preserve at larger size not “normal use size”… (just as I suspected!) Anatomies of bark and wood are different. Considerable amount of literature on bark- anatomy, chemistry, resin.  Includes great bibliography with paper

++Jakes, K.A. and L.R. Sibley. (1983)  “Survival of Cellulosic Fibres in the Archaeological Context.” In Science and Archaeology. No. 25, pg 31-38. 1983.

* Jeberien, Alexandra and Malcolm Bilz.  (2000) “Comparison of Air Dried and Freeze Dried Solutions of Polyethylene Glycol 3350”  In ICOM WOAM Newsletter No. 31 June 2000.

Ellen Carrlee’s notes: They expected all to line the walls and bottom of beakers.  Air dried samples had consistency of beeswax and occupied only the bottom the beaker, might have lined walls if they were more porous?  Freeze dried samples had a powdery matrix appearance and occupied the full volume that the frozen water/PEG mix had originally occupied.  For the freeze-dried, when they were returned to low temperature, higher concentrations that had been freeze-dried (20% and above) showed some concentrated PEG solution at the bottom of the beaker that had not been able to get past plugs of PEG.  5% did not have that, so water must have escaped.

*++ Jensen, Poul; Grethe Jorgensen, Ulrich Schnell.  (2002) “Dynamic LV-SEM Analyses of Freeze Drying Processes for Waterlogged Wood”  Proceedings of the 8th ICOM Group on Wet Organic Archaeological Materials Conference, Stockholm, 11-15 June 2001 pp.319-333

Ellen Carrlee’s Notes: Looking at distribution of PEG in wood with Low Vacuum Scanning Electron Microscopy (can avoid sputter-coating of SEM and the bias it introduces.)  Machine itself acts like a freeze-dryer with wet samples.  Phase diagrams for PEG done by different authors usually don’t agree, but they all agree the eutectic is around 55% (w/w) for all the mw of PEG.  Eutectic temperatures are not in agreement.  Below the eutectic temperature, a solid lamellar eutectic phase forms between the ice crystals.  Phase diagram they suggest for PEG 6000 shows solid PEG as well as a solid PEG/ice mixture at freezing temperatures with a concentration above 55% (eutectic.)  Below the eutectic, all PEG solutions result in 3-9% expansion at temps below freezing.  Ice has 9% expansion, PEG has 7% volumetric contraction.  Is this a primary function of the PEG?  PEG solutions below 55% all expand on solidifying.  PEG concentrated in the later wood and distributed irregularly in the early wood.  Collapse can be avoided if we stay below the eutectic temperature.  When ice forms, the PEG gets more concentrated.  Formation of large ice crystals contributes to uneven distribution of PEG.  Even distribution of PEG is only possible for eutectic concentrations.  PEG has a low affinity for the secondary cell wall (Jensen’s PhD thesis from 1995.)  Heating after freeze drying causes the PEG to aggregate on surfaces of cell wall and give better distribution.  They suggest investigating methods to nucleate smaller ice crystals and thus better distribution.

Dana Senge’s Notes: Water will not freeze at normal freezing T.  Aqueous solutions of water-soluble agents like PEG hygroscopically bound to water. Suggests that the only way to have even distribution of PEG with freeze drying process is to hit eutectic.  All other concentrations will consist of pockets of mixtures: eutectic, ice crystals or solid PEG.  Ice crystals or solid PEG  are larger than diameter of cells—leave voids in laminar structure.  Also  “the 9% expansion of ice crystals are only partially counter balanced by 7% volumetric contraction of PEG.” Also—only tested single step impreg. System—not two step system

* Jenssen, Victoria and Lorne Murdock.  (1982) “Review of the Conservation of Machault Ships Timbers: 1973-1981”  Proceedings of the ICOM Waterlogged Wood Working Group Conference Ottawa 1981. pp. 41-49

Ellen Carrlee’s notes: Mostly oak, preserved in anoxic silt in shallow brackish tidal area.  Initial treatment to try slow drying by burial in wet sand.   After five years, they didn’t seem to be drying out, plus sand was contaminated with sodium chlorophenate.  Treatment 2 was spraying the timbers for two years, intermittently, with PEG 540 15% because 25% didn’t seem to soak into the wood.Treatment 3 was applying thick PEG 540 directly to the timbers every 6 months, and this was absorbed very quickly in room at 18C and 80% RH.  Treatment 4 had not yet happened when this was published, they were aiming for display by 1984.

*++ Johns, Dilys A. (1998)  “Observations Resulting from the Treatments of Waterlogged Wood Bowls in Aoteroa (New Zealand) in Hidden Dimensions WARP Occasional Paper 11, UBC Press.  Vancouver: Canada.  pg 317.

Dana Senge’s notes: Two forms of treatment used at University of Aukland.  Before 1986: one step impregnation with incrementally increasing concentrations of aquaeous PEG 3350 followed with freeze drying from 5-40% over 6-12 months followed with freeze drying.  After 1986: two step process pretreated with PEG 400 than 3350. Conservators were forced to try slow air drying in 1987 following PEG treatment (pieces too big for freeze drying)—had good results.  Felt that they could halt air drying and continue impregnation if needed. PEG shrinks in freezing—thought to counteract expansion of freezing water.

Ellen Carrlee’s notes:  Supports other literature (Hoffmann ) that indicate the two-step PEG method is better for wood that includes both sound and deteriorated areas.

* Jover, Anna.  (1994) “The Application of PEG 4000 for the Preservation of Palaeolithic Wood Artifacts.”  Studies in Conservation, Vol. 39, No. 3 pp 143-165.

Ellen Carrlee’s notes: Charred wood from 45,000 years BP, pinus sylvestris and juniperus.  80% solution of PEG 4000 at 100C was used.

* Kaenel, Gilbert.  (1994) “PEG Conservation of a Gallo-Roman Barge from Yverdon-les-Baines (Canton of  Vaud, Switzerland.)”  Proceedings of the Fifth ICOM Waterlogged Archaeological Materials Conference.  Portland, Maine 16-20 August 1993.  pp. 143-165.

Ellen Carrlee’s notes: Mostly oak, treated in a tank with PEG 4000 raised from 15% to 85% at 60C over 18months of impregnation.  AD 400.  Slow drying, natural looking finish reported.

++Karchut, Jeremy.  (2008) “Spruce Root Collecting at Fish Bay” website: http://www.fs.fed.us/r10/ro/sd_notes/summer_07/spruce_root/spruce_root.shtml , accessed November 2008.

Dana Senge’s notes: Describes experience gathering materials and preparing them for weaving with Teri Rofkar, Tlingit weaver.

*++ Kaye, Barry and David J. Cole-Hamilton (1998)  “Supercritical Drying of Waterlogged Archaeological Wood” in Hidden Dimensions .  pg 329.

Dana Senge’s notes: Supercritical carbon dioxide used for drying process.   Shrinkage is a little greater than freeze drying.  Good for composite objects that can’t be treated with PEG or materials that resist PEG treatment. One example—hemp rope was very brittle requiring additional consolidation

Ellen Carrlee’s notes: Only 3 methods to remove the water: air dry, freeze dry, and supercritical dry. Air dry has liquid turn to gas, but liquid vapor surface moves through the object and may cause damage. Freeze dry turns the liquid to a solid and then with low temp and pressure the solid goes to a gas through sublimation, but cryprotectants needed because of the 8% volumetric expansion of water as it turns into ice.  Supercritical drying goes from liquid to gas without crossing liquid-gas boundary using the supercritical region where distinction between gas and liquid ceases to apply.  Need to replace water with a solvent (methanol, risk of soluble components) then replace the solvent with high pressure liquid carbon dioxide, and then heat it until it goes beyond the critical point.  Equipment and chemical intensive (need an autoclave).  Temps range from -78C to 50C during treatment. Compression/decompression risks.  Lighter color, poor tolerance to changes in environment, poor mechanical properties in some cases.

* Keene, Suzanne.  (1982) “Waterlogged Wood from the City of London.”  Proceedings of the ICOM Waterlogged Wood Working Group Conference Ottawa 1981 pp. 177-180

Ellen Carrlee’s notes: Variety of different hardwoods and softwoods.  PEG 4000 was use up to 90% at 50-60C, but wood came out dry and splintery so they switched to PEG 1500.  Rinsed with hot water, wrapped in towels and dried slowly in the dark.  Objects come out heavy, brittle, but not much shrinkage.  A little darker, and fine detail is preserved.  For freeze drying, PEG 400 left the wood too fragile, 40-50% PEG 1500 or 4000 worked better.  She’s down on acetone/rosin because while other colleagues have had luck with metal handled tools, she’s not had the best luck and working with hot acetone is difficult.

Lindblad, Cecilia and Ingmar Persson. “Polyethylene Glycol/ Polyethylene Oxide: An Overview of the Physical-Chemical Properties of PEG/PEO”  Presented at the ICOM-CC Working Group on Wet Organic Archaeological Materials Amsterdam,10-15 Sept.  2007.  Not yet published.

Ellen Carrlee’s notes: Persson generously sent me a copy.  Describes a lot of chemistry of the polymer.  There’s no clear distinction between PEG/PEO.  PEG extremely soluble in water, but solubility of PEO actually decreases with high temps, salt, and strong stirring.  Exponential increase in viscosity with higher molecular weight.  Bonding discussed.  Hydration radius for PEG 4000 at 30C is 50 nm.  High mw PEGs  above PEG 1000 form random coils and low mw PEGS below PEG 600 maybe form stretched aggregate chains?  PEG on objects treated with high temps show signs of decomposition.

MacLeod, Ian D. (1990) “Conservation of Waterlogged Timbers from the Batavia 1629.”  The Bulletin of the Australian Institute for Maritime Archaeology. Vol 14 No 2 1990 pp1-8

++ Martin, Robert and John B. Christ. (1970)  “Elements of bark structure and terminology” in Wood and Fiber. Vol 2, no. 3, pg 269-279. 1970.

Dana Senge’s notes: Inner bark: physiologically active tissues between the cambium and the last formed periderm=phloem. Outer bark: layer of dead tissue-outside the last formed periderm—rhytidome.

* Masuzawa, Fumitake, Makiko Okuni.  (2002) “Study on Change of PEG Impregnated Waterlogged Wood over Twenty-Eight Years.”  In Proceedings from the 8th ICOM Group on Wet OrganicArchaeological Materials Conference.  Stockholm, 11-15 June 2001 pp. 606-607.

Ellen Carrlee’s notes: Humidity in Nara where these artifacts are is high in the summer.  Waterlogged oak with water content 660% treated with PEG 1500blend, 2000, 4000, and 4000S.  Concentrations were 20%, 40%, 60% and 80% as well as molten at 100%.  PEG 4000 in solution (not the molten) performed the best.

++Masuzawa, Fumitake; Ueda, Naomi; Inoue, Michiko; Kawamoto, Kozo. (1999) “Screening Some Methods for Conserving and Restoring about 500 Objects of Waterlogged Japan ware” Proceeding of the 7th ICOM-CC Working Group on Wet Organic Archaeological Materials Conference, Grenoble, France 1998. pg 268-274.

Dana Senge’s notes: Treatment of Urushi objects  (mostly bowls and plates)

Earliest 1957: coat with acrylic resin, no records, artifacts not highly damaged/degraded.

1970’s: soaking objects in 20% PEG 4000 and concentrations up to 100%.  Useful on objects with urushi layer in good condition, thin urushi layer would start coming off, peeling into pieces due to heated and concentrated PEG.

1980’s (early):  Alcohol-xylene-resin.  1) start by replacing water with ethanol, 2) then xylenes 3) then xylenes, rosin and damar.  Not heated, but thin low urushi layers still peeled and curled when replacing water with alcohol.  Drying oils in Urushi and charcoal powder in ground damaged by heat and org. solvents in these processes.

1991:  freeze drying, tested concentration of PEG 4000 and cooling rate/temp.

tests: Impregnation 20% PEG 4000 (2 weeks) Impregnation 40% PEG 4000 (4 weeks) Prefreeze, then 2 week Freeze Dry. Impregnation short—to have little effect on urushi.

Masuzawa, Fumitake.  (1973?) “Experiments on the Impregnation of Waterlogged Wood with PEG Part I”  Conservation Science Bulletin.  Hozon Kagaku Kentyushitsu Kiyo.  Vol. 2 1973?  pp5-11

Ellen Carrlee’s notes: this is from a literature review in ICOM-CC WOAM Newsletter No 8 Nov 1982.  Samples of waterlogged oak with 650% water content pre-treated with EDTA and then 20%, 40%, 60% and 100% PEG 3300, 2000, and 540 blend at 60C for 21 days.  Impregnation incomplete.  PEG 540 blend continued to ooze out, and PEG 3300 and PEG 2000 caused darkening.

Masuzawa, Fumitake and Yoichi Nishiyama.  (1974) “Experiments on the Impregnation of Waterlogged Wood with PEG Part II”  Conservation Science Bulletin.  Hozon Kagaku Kentyushitsu Kiyo.  Vol. 3 1974 pp39-46

Ellen Carrlee’s notes: this is from a literature review in ICOM-CC WOAM Newsletter No 8 Nov 1982.  Size greatly affects time for saturation: 50-60 days for 3cm wood, but more than 120 days for oak of 7.5cm

Masuzawa, Fumitake and Matsuda Takatougin. (1974)  “Surface Treatment for the Removal of Dark Hue on Waterlogged Wood Impregnated with PEG.”  Conservation Science Bulletin.  Hozon Kagaku Kentyushitsu Kiyo.  Vol. 3 1974 pp 47-51

Ellen Carrlee’s notes: this is from a literature review in ICOM-CC WOAM Newsletter No 8 Nov 1982.  Swathing the wood in cotton bandages soaked in ethanol.

Masuzawa, Fumitake. (1974)  “Change of Waterlogged Wood Impregnated with PEG Along the Lapse of Time.”  Conservation Science Bulletin. Hozon Kagaku Kentyushitsu Kiyo.  Vol. 3 1974 pp. 52-58

Ellen Carrlee’s notes: this is from a literature review in ICOM-CC WOAM Newsletter No 8 Nov 1982.    Reviewing wood treated with PEG after one year.  Wood treated with PEG 540 blend absorbed moisture, oozed out and there was shrinkage.  PEG 2000 showed radial cracks after 3 months and some expansion.  PEG 3300 showed no great change.  Based on other articles, they were probably looking at oak.

* McCawley, J.C. (1977) “Waterlogged Artifacts: The Challenge to Conservation.”  In Journal of the Canadian Conservation Institute.  Vol 2, 1977. pp17-26.

Ellen Carrlee’s notes: Good description about waterlogging on the cellular level.  Many older treatment methods described.

*++McCawley, J.C., David Grattan, Clifford Cook.  (1982) “Some Experiments in Freeze-Drying: Design and Testing of a Non-Vacuum, Freeze Dryer” in Proceedings of the ICOM Waterlogged Wood Working Group Conference.  Ottawa 15-18 September 1981. pg 253-262.

++ McKerrell, H, E. Roger and A Varsanyi. (1972)  “The Acetone/Rosin Method for Conservation of Waterlogged Wood.”  In Studies in Conservation Volume 17, 1972. pg 111-125.

Dana Senge’s notes: Grosso used this procedure with some pieces at Ozette that were not stabilized with PEG Treatment.  Heartwood of Oak—very little deterioration after thousands of years.  Compared treatment to standard PEG 4000, 20% in water.  Procedure:  Initial treatment with dilute 3-5% HCL followed by thorough washing. Dehydrate the wood – immersion in three baths of acetone over a period of two weeks. Impregnation with rosin (colophony) saturated acetone @ 52 degrees C followed by evaporation of solvent.  (rosin 67% w/w of liquid.

* McConnachie, Glenn; Rod Eaton and Mark Jones. (2008)  “A Re-Evaluation of the Use of Maximum Moisture Content Data for Assessing the Condition of Waterlogged Archaeological Wood.”  E-Preservation Science, Morana RTD 2008.

Ellen Carrlee’s notes: took maximum moisture content (Umax) profiles from oak, poplar, and pine and compared it to visible degradation patterns for timbers that have a more degraded surface and more solid core.  Took Umax modern plus 50% to come up with limit for what is to be considered degraded: oak is 150%, poplar 400% and Scots pine 250%.  Conservators typically assess timbers by probing, taking core samples and getting Umax from fragments.

*Mitchell, H.L. (1972) “How PEG Helps the Hobbyist Who Works With Wood. “  US Dept of Agriculture Forest Service Forest Products Laboratory, Madison Wisonsin.

Ellen Carrlee’s Notes: Interesting info on what adhesives are recommended with PEG

++ Morgos, Andras and Setsuo Imazu. (1994) “Comparing Conservation Methods for Waterlogged Wood Using Sucrose, Mannitol and Their Mixture.”  In Proceedings of the 5th ICOM Group on Wet Organic Archaeological Materials. Portland, Maine 16-20 August 1993. pp 287-299

Dana Senge’s Notes: Sugar and Mannitol have excellent dimensional stability. Mannitol: smaller molecules, good diffusion characteristics, penetrates quickly, stabilizes wood structure before collapse, food for less degraded woods, lower water solubility than sucrose—therefore it crystallizes before sugar upon evaporation or lower temperature. Sucrose: higher molecular weight than mannitol, a little lower penetration compared to mannitol, forms larger crystals, has higher solubility—is good for mid to high deterioration and bulks the voids in the system.  2 step PEG process minimizes greasy/waxy effect.  (Mixture of high and low mw of PEG will not solidify upon drying—resulting in greasy/waxy surfaces) Authors tested theory of two step method with sugar/mannitol—combining to one treatment step.  Testing was performed on Japanese woods of various levels of degradation.  Results:  Sugar and sugar/mannitol treatments effective. ASE a little higher with blend.  Mannitol alone—ineffective on low degraded material, whitens material surface when used in concentration higher than 51.2%

++ Morgos, Andras and Setsuo Imazu.  (1993) “A Conservation Method for Waterlogged Wood using a Sucrose Mannitol Mixture”  In ICOM-CC 10th Triennial, Washington D.C., 22-27 August 1993 Preprints. 1993. Pg 266-272.

Dana Senge’s Notes: Very similar to 1994 article.

Morrison, Lynn  (1989) “Treating Waterlogged Moss Rope”  ICOM-CC Working Group on Wet Organic Archaeological Materials Feb 1989

Ellen Carrlee’s notes: No details of the PEG treatment given in abstract

* Muncher, D.A.  (1991) “The Conservation of WLF-HA-1: the WHYDAH Shipwreck Site.”  The International Journal of Archaeology.  1991.  20.4:335-349

Ellen Carrlee’s notes: Wood in 10% PEG 400 unheated, every 2 weeks, concentration increased by 10% until 50% concentration reached after 10 weeks.  Easier to change solutions than add biocides.  Freeze dried.  Afterwards, PEG 3350 applied with brush in molten state, cooled with blow dryer and excess removed with cheesecloth.

* Murray, Howard.  (1982) “The Conservation of Artifacts from the Mary Rose.” Proceedings of the ICOM Waterlogged Wood Working Group Conference Ottawa 1981. pp. 12-19

Ellen Carrlee’s notes: Wood treated was poplar, oak, ash and softwoods.  Passive holding included spraying with boric acid and double wrapping in sealed polyethylene sheeting (dried out somewhat and got cracking and salt efflorescence within 6 months) or submersion in water (resulting in additional expansion and softening.)  Pre-treatment with 5% EDTA as well as ultrasonic cleaning to remove salts and iron corrosion products, although more than 48 hours in EDTA resulted in notable softening.  PEG 3400 up to 50%.  Mostly doing freeze drying, although getting good results with drying only the surface in the freeze drier and then allowing it to air dry.  Excess PEG removed with hot air, IR lamps, and ethanol swabs.  Reconstruction done with wooden dowels, nitrocellulose adhesive and melted PEG 6000 at 50% as a surface coating.

Park, J.  (1997) “The Barton-on-Humber Project: A Large Collection of Waterlogged Wood: Data, Retrieval, Storage, Pre- and Post-Treatment Methods.”  In Proceedings of the 6th ICOM Group on Wet Organic Archaeological Materials, York, 1996.

++Powell, George M. (1980) “Polythylene Glycol.”  Chapter 18 in Handbook of Water-Soluble Gums and Resins ed. By Robert L. Davidson.  New York: McGraw-Hill.  pp 18-31.

++ Purdy, Barbara. (1996)  How to do Archaeology the Right Way. University of Florida Press. Gainesville, Florida.

Dana Senge’s notes: Chapter 4  Degradation, Preservation and Curation. Favorable conditions in natural environments that prevent degradation of plan and animal material…locations that remain continuously frozen, wet or dry  (stability of environment). Her standard PEG treatment:  10% PEG (preferably 540) increased incrementally by 10% each month until you reach 80%  (~ 8 months) Noted that PEG used to treat cordage, nets and baskets require different molecular weights. Example of textile from Windover Site: freeze dry and treated with parylene. Sugar another option but attracts insects.  Refers to PEG as similar to antifreeze.

Ellen Carrlee’s notes: Purdy is an archaeologist teaching in the field since 1967.  She has conservation awareness, attended the 1981 WOAM conference in Ottawa, for example.

* Rice, J.T.(1990) “Glueing of Archaeological Wood,”  In R.M. Rowell and R.J. Barbour (editors) Archaeological Wood Properties, Chemistry and Preservation. Advances in Chemistry Series 225, American Chemical Society.

Ellen Carrlee’s notes: includes info about adhering PEG treated wood and suggests solvent systems are better than aqueous ones for that purpose, which is helpful for thinking about consolidation too.

* Rodgers, Bradley.  (1992) ECU Conservator’s Cookbook: A Methodological Approach to the Conservation of Water Soaked Artifacts.   Chapter 2: “Waterlogged Wood.”  Herbert P. Paschal Memorial Fund Publication.  East Carolina University.

Ellen Carrlee’s notes: ECU= East Carolina University.  Dr Bradley Rodgers teaches conservation of material from underwater environments. Don’t put items from saltwater directly into fresh water, needs to be gradual or the salt water moves out faster than freshwater can move in, causing collapse (ie pruny fingertips in the bath.)  Specific gravity of several woods are given.  Pits in cell walls have valves, and if these are blocked it is harder to impregnate the wood.  Hard to see w/o SEM.  PEG solution is heated, and you weigh it weekly after you achieve 50% PEG.  Should stabilize at about 20% weight gain.  Might go up to 35%.  If you’re using PEG 3350, maybe even 45%  Wood in good condition sometimes as little as 15%.  Sucrose treatment described.  Brush coating of 50% PEG 3350 to consolidate the outer layer.  Ellen’s note: Bradley’s treatments don’t always match up to AIC standards and ethics, and there was a big dustup over one of his recent publications, an update and expansion of the material in this book.  Does this say more about AIC or about Rodgers?  What is really going on with AIC and the archaeology world anyway?

*++ Rowell, Roger M. and R. James Barbour (1990) (editors) Archaeological Wood Properties, Chemistry and Preservation. Advances in Chemistry Series 225, American Chemical Society. Washington DC.

Dana Senge’s notes: Valuable text include articles by Florian on history of archaeological wood, treatments, storage, future research.

* Sakuno,Tomoyasu, and Arno P. Schniewind.  (1990.)  “Adhesive Qualities of Consolidants for Deteriorated Wood.”  Journal of the American Institute for Conservation.  Vol. 20. No. 1. 1990 pp.33-44.

Ellen Carrlee’s Notes: For dry archaeological wood not treated with PEG, The adhesive strength of Butvar B-98 for glue line impact shear strength was higher than B-72 and AYAT but less than PVA emulsion.  Butvar, B-72 and AYAT are all effective consolidants, it seems.

* Saupe, Dr. Stephen G.  (2009) “Cell Walls –Structure and Function” Plant Physiology (biology 327) College of St. Benedict/ St. john’s University. Collegeville, Minnesota. 2009. http://employees.csbsju.edu/ssaupe/biol327/Lecture/cell-wall.htm

Ellen Carrlee’s notes: good description of the cell wall using plain language but lots of detail.  Hemicellulose is now called “cross-linking glycans.”  Good discussion on bonding and formation as well.

* Schaffer, Erika. (1976) “The Preservation and Restoration of Canadian Ethnographic Basketry.” Studies in Conservation. Vol 21 no. 3. 1976
Ellen Carrlee’s notes: 25g PEG 600, 20g glycerine dissolved in a 75% aqueous ethyl alcohol solution to yield 100g.  Applied with a brush on both sides of the basket (birch bark) daily.  Treatment done in 1970, but the entire article ONLY deals with deformed DRY material…this article is not about waterlogged material at all, or even damp stuff.

++ Schindelholz, Eric et all.  (2007) “An Evaluation of Supercritical Drying and PEG/Freeze drying of Waterlogged Archaeological Wood.”  A report for NCPTT grant. 2007

Dana Senge’s notes: Compared PEG/Freeze drying, Air drying, Supercritical Drying. Overall PEG/Freeze drying gave best treatment results, least amount of shrinkage. (similar results to Barry Kaye).  PEG=cryoprotectant.  Supercritical drying technique:  replace water with methanol (methanol exchange process) for a period of 4 weeks (length of solvent exchange treatment determined time through methanol endpoint determination)*, pins set in samples and measured to track shrinkages, then run in batches through supercritical drying system. *test samples were placed in methanol baths.  New baths every 7 days.  Old baths were analyzed using Karl-Fischer titration to determine water concentration.  Water content was less than 5% after 2 weeks and 1% after weeks 3 and 4.

*Schniewind, Arno P. and Peter Y. Eastman.  (1994)  “Consolidant Distribution in Deteriorated Wood Treated with Soluble Resins.”  Journal of the American Institute for Conservation. Vol. 33, No. 3, 1994.  pp 217-255.

Ellen Carrlee’s notes: SEM investigation into dry deteriorated archaeological wood not treated with PEG, but consolidated with B-72, Butvar B-90 and Butvar B-98. Resin was not uniformly distributed.  Reverse migration is blamed.

*Schniewind, Arno P. and Carlson, S.M., (1990) “Residual Solvents in Wood Consolidant Composites.”  Studies in Conservation. Vol. 35, No 1. Feb 1990.

*++Schniewind, Arno P. (1990) “Consolidation of Dry Archaeological Wood by Impregnation with Thermoplastic Resins.”  In Rowell, R.M. and R.J. Barbour (1990) (editors) Archaeological Wood Properties, Chemistry and Preservation.  Advances in Chemistry Series 225, American Chemical Society. Washington DC

Ellen Carrlee’s notes: Suggests Butvar B-98, Acryloid B-72 and AYAT as the most likely resins to be successful in consolidating dry archaeological wood (not treated with PEG)

*Seborg, Ray M. and Robert B. Inverarity. (1962) “Conservation of 200-Year-Old Water-logged Boats with Polyethylene Glycol.” Studies in Conservation.  Vol 7 No 4 1962 pp. 111-120

Ellen Carrlee’s notes: Similar to Science article.  Wooden boats 200-300 years old in Lake George excavated, made of white and yellow pine as well as white oak.  Oak was OK, but pine badly degraded.  50% PEG 1000 was used at room temp from 4 hours to three weeks, and by multiple dip treatment.  Wood was air dried at 80F and 30% RH.  When treated for 7 days, the white pine had 60% retention of PEG, yellow pine had 35% and white oak 13%.  Treating the white pine for 2 days was as effective as treating it for 7 or 21 days.  Wood treated this way gets damp above 80% RH and sweats at 90%.  Reduced solubility of PEG with a higher molecular weight can be easily overcome by a moderate increase in temperature.

*++ Seborg, Ray and Robert Bruce Inverarity. (1962)  “Preservation of Old, Waterlogged Wood.” From Science: 18 May 1962, vol 136 no. 3516. pg 649-650.

Dana Senge’s Notes: Sited by Grosso and others as starting recipe for treatments at Ozette, Conway, Wapato.  Process used to dry 200 year old waterlogged boats from Lake George, NY.  Recognizes that treatment of waterlogged wood has been a problem for archaeologists and museum conservators for a long time.  Experiments done by Adirondack museum in Blue Mountain Lake NY and US Forest Products Lab in Wisconsin.  Treatment: 50% PEG 1000 in 50% aqueous soln, room temp for 4 hours to 1 week and multiple dip treatments, Dried @ 80 degrees F and 30% RH.  Shrinkage observed: untreated = 5-7%  Treated for 2-7 days=0.5%.  Shorter treatments 4-24 hours=2-4%.  Observed improvement in reduction of surface checking regardless of treatment length.  Materials were 1/2-1” thick planking (white oak, white and yellow pine) Noted—Wood treated with PEG 1000 becomes damp under high moisture conditions: above 80% RH (will sweat or bleed at 90% RH)  Recommends higher molecular weight because it is less hygroscopic (may require heat to facilitate impregnation).

* Singley, Katherine. (1988) The Conservation of Archaeological Artifacts from Freshwater Environments Lake Michigan Maritime Museum, South Haven, Michigan 1988.

Ellen Carrlee’s notes: She tends to use PEG 300 and 400 with 4500 applied later hot.  Recommends pretreating wood contaminated with iron salts with 3% perchloric acid, soaked for about a week.  This dissolves iron and opens up the pore structure to increase the penetration of PEG.  PEG 300 at room temp 10% for six months, then removed and wrapped in plastic with regular surface brushing of higher concentrations 3X a week increasing the concentration every two months until 80% reached.  Slow drying at high RH was used.  50% PEG 4500 paste was then applied with hot air.  This layer was thought to prevent oozing out of lower MW PEG.  She also uses 10% PEG 300, soaked for a year and then freeze dried.

* Smith, C. Wayne. (2005) “Rethinking Conservation Paradigms for the Preservation of Waterlogged Wood.”  WAG Postprints, Minneapolis Minnesota.  2005.

Ellen Carrlee’s Notes: PEG decomposition creates aldehydes, ferrous, ferric, and cupric salts.  Trouble with PEG when it interacts with compounds and oxides found in waterlogged wood.  PEG treatments cause some cellular collapse or cell wall distortion.  Long term reactivity of PEG is an issue.  Smith likes polymerization as a technique.

* Smith, C. Wayne  (1997) Retreatment of PEG Treated Waterlogged Wood Conservation Research Laboratory Texas A&M.  1997

Ellen Carrlee’s notes: Claims that PEG becomes unstable over time and there’s movement within the wood.  Suggests method for retreatment extracting PEG and crosslinking remaining PEG. Ellen’s note: there are more references where Smith discusses the shortcomings of PEG.

++Smith, Derek. (1964) Archaeological Excavations at the Beach Grove Site, DgRs1, During the Summer of 1962.  BA Thesis. UBC

Dana Senge’s notes: Site was shell midden, NE corner of Point Roberts Peninsula in Delta Municipality, BC.  Fiber materials were found in stratum of finely textured blue clay at eastern fringe of midden—adzing detritus and twisted rood strands including basketry.  Pg. 50 describes Basketry/Matting found in clay layer. Radiocarbon date of charcoal at site: 363 +/- 120

* Spirydowicz, K.E., E. Simpson, R.A. Blanchette, A.P.Schniewind,  M.K.Toutloff, A. Murray, (2001), “Alvar and Butvar: The Use of Polyvinyl Acetal Resins for the Treatment of the Wooden Artifacts from Gordion, Turkey”, Journal of the American Institute for Conservation, Vol. 40, No. 1, 2001, pp 43-57.

Ellen Carrlee’s notes: the wood was not PEG treated.  This is one of the important studies regarding Butvar B-98 on archaeological wood.  It was used 10% in 60:40 ethanol and toluene.

* Stamm, A.J. (1959) “Effect of Polyethylene Glycol on the Dimensional Stability of Wood.”  Forest Products Journal, Vol. 9 No 10 October 1959. pp373-378.

Ellen Carrlee’s Notes: Typical of early literature on PEG, many more articles like this one at the ASM conservation lab.  Stamm was looking into PEG as early as 1956.  Green wood soaked overnight in 30% PEG 1000 is recommended.  Gluing tests are described.

* Stark, Barbara L. (1976)  “Waterlogged Wood Preservation with Polyethylene Glycol.”  Studies in Conservation Vol. 21. 1976 pp.154-158.

Ellen Carrlee’s notes: 1969 excavation Alvarado, Veracruz, Mexico found wooden bowls with polychrome painting, around AD. 300, Gliricidia sp., in brackish water.  PEG 1540 was chosen because PEG 1000 would be hygroscopic in conditions about 80% RH.  Did not use PEG 4000 because she feared it would loosen the paint and she did not want to use heat.  Tried 13 days soaking in saturated solution of PEG 1540 at 28C, thought to be over 70%.    Larger pieces soaked 60-75 days.  Added more PEG as time went on a wood absorbed it.  Slowly air dried in a humid environment.  Shrinkage up to around15% and minor warpage. Glued together with Duco before fully dry

Dana Senge’s notes: Waterlogged wooden bowl with polychromy–  Alvarado, Veracruz, Mexico. No Field Treatment- shipped to New Haven for treatment—shipment delays from field to lab caused some drying. Treatment: Carbowax 1540 selected—1000 is hygroscopic @ humidity conditions about 80%– not as much of an issue with 1540—but still damp when handled?

Storch, Paul.  (1997) “Non-Vacuum Freeze-Dry Treatment of Two Leather Objects.” in Leather Conservation News. Vol 13 no 2. 1997. pg 15-17.

Dana Senge’s notes: Described Peg Treatment of two leather boots followed by freezing then freeze drying in non vacuum freeze drier.  Freeze drying: objects placed in polypropylene container with silica gel.

Ellen Carrlee’s Notes: Might be helpful for us in drying PEG treated basketry without a freeze dryer using a low-temp freezer.

* Straetkvern, Kristiane. (2002) “Freezing of Polyethylene Glycol: Compressions Strengths and freezing Curves for High-Molecular Weight PEGs with and without Low-Molecular Weight PEGs Added.”  In Proceedings from the 8th ICOM Group on Wet OrganicArchaeological Materials Conference.  Stockholm, 11-15 June 2001. pp.335-352.

Ellen Carrlee’s notes: Straetkvern suggests compression strength of wood is greater for high molecular weight PEG treatments done without low molecular weight PEG.

* Titus, Larry.  (1982) “Conservation of Wooden Artifacts.”  Proceedings of the ICOM Waterlogged Wood Working Group Conference Ottawa 1981. pp153-158.

Ellen Carrlee’s Notes: Excavation in 1978, help from the Museum of Archaeology and Ethnology at Simon Fraser University and Dept of Archaeology indicated that previous waterlogged basketry and cordage did not have successful treatment, with PEG flaking off or crystallizing on surface of fragile artifacts.  So they soaked the hardened fatyy midden matrix from the surface with acetone and painted with Neatsfoot oil, then immersed in Ethulose if needed.  Seemed to have worked OK with the wood, most of which was fairly sound.  Conservator Charles Hett commented that the good preservation was due to the fat content.  Several hundred wooden pieces excavated from Barrow in 1981 (Utkiavik Archaeology Project)  about 150 treated in the field.  Air dried, brushed to remove dirt, then soaked in water and then PEG 4000 (although some PEG 1000 was used at first.)  Immersion between 48-165 hours.  Then it was air dried and sprayed with Lysol (ortho phenylphenol.)  Wow, I wonder where these pieces ended up?

++ Turner, Nancy J. (1998).  Plant Technology of First Peoples in British Columbia.  UBC Press: Vancouver.

*Unger, Achim; Arno P. Schneiwind, Wibke Unger.  (2001) Conservation of Wood Artifacts: A Handbook.   Natural Science in Archaeology Series. Springer Verlag.  New York.

Ellen Carrlee’s notes: Contains excellent chronological lists of when major treatments and innovations occurred and who did them.

*Viduka, Andrew. (2002)  Survey of Methods Used by Some Large institutions Specializing in the Conservation of Wet Organic Archaeological Materials. Report as the 2002 Churchill Fellow: Winston Churchill Memorial Trust of Australia.

http://www.churchilltrust.com.au/res/File/Fellow_Reports/Viduka%20Andrew%2020021.pdf.

Ellen Carrlee’s Notes: Viduka visited several labs and wrote up his observations.  Texas CRL sees, among other things, darkening of surfaces with high PEG concentrations as a disadvantage.  Parks Canada was looking at whether PEG modifies the crystal size of water.  Tara Grant at CCI has generally found air-drying to be unsuccessful.  Wooden material from Nydam Mose, 5th C Iron Age site treated in Denmark, is highly deteriorated with only lignin remaining.  NMD is looking into sucrose, wood flexibility post-treatment, Cellusolve method, lots of vacuum freeze drying, review of old treatments, deacidification of low mw PEG timbers, experimental cold air drying.  On the Vasa, acid affected areas have white or yellow build-up and generally appear on areas treated with PEG 400 and not PEG 4000.  Remedial treatment is a spray with sodium bicarbonate and soda with a pH >10 and covered with plastic wrap.  Skuldelev ships were some of the earliest to be conserved with PEG 4000, and 40 years later, they still have a mw of 3900.  Using too high a mw on only slightly degraded wood is a problem.  Too much PEG would give a purple or blue sheen on the surface.  Longer immersion made bigger timbers darker than smaller pieces.  Heating for re-shaping caused darkening of the surface. Glenn McConnachie’s PhD reveals that even well-preserved waterlogged oak from the Mary Rose has 30% volumetric shrinkage after air drying.

Vynckier, Jozef.  (1965) “Examination and Conservation of Basketwork from a Roman Well at Destelbergen”  Bulletin de’Institut Royal du Patrimoine Artistique Vol 8.  1965  (Flemish?)

Ellen Carrlee’s notes: Linden bark basketry fragments immersed 4 months in carbowax 4000

*++ Watson, Jacqui.  (2004) “The Freeze-Drying of Wet and Waterlogged Materials from Archaeological Excavations.”  In Physics Education. 39(2) 2004 pg 171-176.

Dana Senge’s notes: Anaerobic conditions may have eliminated decay due to microorganisms but material – wood—will slowly dissolve leaving a ligneous skeleton. Freeze drying-  requires low T (-28-32° C).  dry air flow to remove saturated air from surface of piece.  If air around objects becomes saturated sublimation will cease.

* Watson, Jacqui. (1982) “The Application of Freeze-Drying on British Hardwoods from Archaeological Excavations.”  . Proceedings of the ICOM Waterlogged Wood Working Group Conference Ottawa 1981.

Ellen Carrlee’s notes: Fungal degradation in the cell wall contributes to splintering when freeze-dried.  Mineral deposition or replacement in outer layers is common in archaeological wood, especially with iron.  Sometimes these can be seen as casts of material that is now lost.  Chelating agents etc remove the iron.  But iron also interacts badly with PEG.  Early warning in this article of problems with iron salts and PEG. Even if the soil has low iron content, there is sometimes high iron content in the wood. Oak freeze dried after 10% PEG 400 for 4-6 weeks had deep cracks next to the rays, and some distortion and collapse in some small fibers.  Using 10% PEG 400 and 15% PEG 4000 resulted in less cross checking on the surface.  Wood that underwent freeze-drying without impregnation collapsed, and showed crystals (calcium and sulphur) that precipitated out that did not do so when PEG was used.  Pitting details in the vessels that are useful for ID were obscured after treatment with PEG 4000.  Mixed PEG solutions work best when using freeze-drying.

*++ Wevers, Anton J.M.  (1991) “Treatment of Waterlogged Rope”  Proceedings of the 4th ICOM Group on Wet Organic Archaeological Materials Bremerhaven 1990.

Ellen Carrlee’s notes: Under PEG 1000 does not strengthen and over PEG 1000 makes it too stiff.  Cleaned, dried, then impregnated with polyurethane

Dana Senge’s notes: Rope—highly processed cellulose fibers. PEG treatments of MW lower than 1000 do not strengthen; above 1000 no more flexibility. Other impreg options: Cellulose derivatives: hydroxy propyl cellulose and PEG 400, Freeze dry, Polyurethane (E2250—not reversible,) Polymers, Luvis-kol and PEG 4000 Author focused on polyurethane treatment—felt that reversibility wasn’t necessary. Noted- circulation of impregnation bath is important to ensure maintaining equal concentration of liquid in bath and in specimen.

* Wyatt, Mary Pat. (1978)  Museum Alaska Newsletter.  Vol. 11 No 1. 1978.

Ellen Carrlee’s Notes: Carbowax 540 Blend or Carbowax 4000 from Union Carbide as well as PEG 1500 or 4000 from Dow Chemical.  Apparently, PEG could sometimes be found in Anchorage lumber stores.  Mixed to a 50% solution and soaked for a month or two, then removed from the 50% solution and soaked in an 80% solution for several months.  Rinsing with hot water followed by slow drying in high humidITy was recommended.  Thymol and Roccal were the recommended fungicides.  Seems to be an article Mary Pat wrote up for Alaskan museums using Grosso 1976 and Stark 1976 as references.  The Alaska State Museum also was offering limited supplies of PEG and thymol.

* Young, Gregory S.  (1990) “Microscopy and Archaeological Waterlogged Wood Conservation.”  CCI Newsletter, No. 6, September 1990.  pp 9-11.

Ellen Carrlee’s notes: General overview of PEG treatment/ research.  Deterioration greatly improves the ability of PEG to penetrate and treat wood successfully, but most excavated waterlogged wood is only moderately deteriorated.  White oak, various cedars, and white ash are hard to penetrate, while aspen, cottonwood, alder and spruce allow greater penetration.  Caution with determining degree of deterioration from thin 3mm cross sectioned wafers of wood examined under the microscope, as the sample has a lot of disrupted wood cells and suggests more cell wall accessibility than there really is.

Young, Gregory S. and Richie Sims. (1989) “Microscopical Determination of PEG in Treated Wood – the Effect of Distribution on Dimensional Stabilization.”  Conservation of Wood and metal: Proceedings of the ICOM Conservation Working Group on Wet Organic Archaeological Material and Metals.  Freemantle, Western Australia Museum. 1987 pp109-140

Ellen Carrlee’s Notes: Fluorescence microscopy.  25-35% PEG 200 and 3350.  Found less penetration with larger molecular weights.  Dimensional stabilization correlates with full impregnation of secondary cell wall.  Eight different species tested showed broad range of access to cell wall.

*Young, Gregory S. (1982) “Polyethylene Glycol Localization within the Structure of Waterlogged Wood.”  9th International Congress on Science and Technology in the Service of Conservation.  1982.

Ellen Carrlee’s Notes: Cobalt thiocyanate staining shows that stabilization depends on how much water is replaced by PEG in cell walls, and also the molecular size of the PEG.  In Aspen wood (Populus sp) PEG 400 penetrates the capillary network in cell wall, but at 35% much better than 15%.  PEG 3350 does not penetrate the capillary network as well.

*Young, Gregory S. and Ian N.M. Wainwright.  (1982) “Polyethylene Glycol Treatments for Waterlogged Wood at the Cell Level.”  Proceedings of the ICOM Waterlogged Wood Working Group Conference Ottawa 1981.  pp.107-116

Ellen Carrlee’s notes: Shrinkage happens when hygroscopically bound water within the cell walls is lost when wood is below the fiber saturation point (FSP.)  Lower MW PEG is expected to stay in the cell wall, while higher MW PEG bulks the lumina.  Cobalt thiocyanate is a microscopical stain when dissolved in non-aqueous histological grade cedarwood oil.  The oil (cedrene and cedrol) is immiscible with both water and PEG.  It  dissolves the cobalt thiocyanate, but readily gives it up to the PEG in wood sections.

PEG 400 (35%) in cell wall capillary matrix

PEG 3350 (60%) bulked cell lumina

PEG 540 blend (64%) in both cell wall and lumina  540=1450 + 300 together equal MW mixture

Over 3000 shouldn’t get into cell wall, above 2000, should be impeded somewhat.  MW below 400 penetrate better.  PEG must penetrate the cell wall for best dimensional stability.  Double bulking is good, though.

++____ (1976) Field Conservation at Ozette Discussion Session.  September 22, 1976

Dana Senge’s Notes: pg 93: Grosso discusses the needs of the Ozette site: helicopter access a couple times a month, not necessarily regularly spaced.  Means that artifacts cannot be regularly removed from the site.  Set up tanks in the field, can treat many of the materials onsite in one month time period.  Then transfer to Neah Bay after treatment.  Best use of time and specific circumstance.  Pg 94. discussion of polymerized oils on bone combs etc.  Thought to be seal oil (similar to linseed)  was broken down with 1:1:1 dichloromethane:methanol: petroleum ether.  Film documentation of site- Ruth and Louis Kirk as well as KOMO  Pg 96:  questions about soil studies-  observation by Mibach that reddish slime exists at site: iron present in cellular structure of artifacts?  Sulphate reducing bacteria?  Grosso response—sulphate reducing bacteria has been found on occasion- used Cytox to counteract.  Early on used Borax/Boric acid to reduce bacteria and keep solution sterile, but some workers fount it irritating—skin and respiratory

*________(1982) “General Discussion Period Session II Analysis and Classification of Wood.”  Proceedings of the ICOM Waterlogged Wood Working Group Conference Ottawa 1981.  pp.117-121

Ellen Carrlee’s notes: Howard Murray: Exposure of object to higher grade solution leached out the previous PEG of a lower solution.

* _________________ “Treatment for Dugout” Unpublished, pre-1980?  Given to former Alaska State Museum conservator Betty Hulbert by the Anthropology Conservation Lab at the Smithsonian.

Ellen Carrlee’s notes: Build a tank deep enough to allow a foot of liquid to cover the boat, line the tank with polyethylene sheeting.  25% PEG 1000 and 5% solution of Roccal fungicide.  Leave in solution for at least 3-4 months, then evaporate off by lifting the plastic cover until the top of the liquid reaches the boat (This will apparently increase the concentration of PEG?) Then drain tank and air dry very slowly.  Surface may be treated with polyurethane varnish.  There is no evidence that this treatment was ever used at the Alaska State Museum, perhaps Betty Hulbert simply had a copy.