What Do We Know About PEG?

 

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.

 

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 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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2 Responses to What Do We Know About PEG?

  1. [...] What Do We Know About PEG? « Ellen Carrlee Conservation [...]

  2. nate says:

    Thank you Ellen! I am a hobby wood-worker and found this extermely informative. I will certainly be referencing it often.
    Thanks again for putting this together for us!

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