Collections Labeling: Alternate Adhesive Testing

 Ellen Carrlee (Conservator Alaska State Museum), Anna Marie Weiss (student, Queen’s University) and Samantha Springer (Conservator, Cleveland Museum of Art)

1. INTRODUCTION:

B-72 is the adhesive conservators recommend for museum labeling of archaeological artifacts.  Postings on labeling basics and suggestions for assembling a labeling kit are also posted on this weblog.  Properly done, the B-72 technique is legible, durable, reversible, and chemically stable.  However, the handling properties of the B-72 technique cause frustration, including unpredictable bubbling and the sensitivity of many inks to solvents in the adhesive.  There is great temptation to utilize other adhesives in pursuit of better handling properties, ease of application, and local availability.  As a follow-up to discussions at the 2010 Alaska Anthropological Association seminar on Collections Curation, several conservators independently tested several popular adhesive alternatives on bone, wood, metal, stone and unglazed ceramic to assess their performance.  Here are our observations, with some notes on our methodology if others want to test more adhesives.  Gallery of images at the end, you can click to enlarge.

2. SUMMARY:

Water-based adhesives had better handling properties for application.  These included ease of cleanup, single-step application, little odor or fumes, and the ability for the water component of the adhesive to penetrate the paper structure and cause it to drape and conform to uneven surfaces easily.  The thicker water-based acrylics and gels (those that were white and thick) also had the advantage of self-positioning easily.  The labels stayed where they were placed and did not move readily when brushed with a topcoat.  The thinner water-based adhesives tended to pool themselves up (from the water tension) when used on metal samples.  Among water-based adhesives, Golden Acrylic Gel had the best application properties of any adhesives tested.  However, many of these properties that are nice for the short-term convenience of the person applying the labels come at a long-term trade off for the best interests of the artifact.  Some corrode metal, some come off easily in moist conditions, and some are hard to remove without damage to the artifact.

Solvent-based adhesives tend to be more difficult to apply.  Disadvantages to the person applying the label include stickiness, more complicated cleanup, possibility of smearing inks or bubbling, disagreeable odor or fumes, poorer ability of the paper label to conform to uneven surfaces, and tendency to slip around when placed and brushed with a topcoat.  Application with adhesive of higher concentration gave a better result in conforming to uneven surfaces and corners staying down, but has sometimes been reported to be associated with bubbling.  Using a different topcoat with a B-72 barrier layer made the labeling process take longer, required more elaborate cleanup, and petroleum-distillate based topcoats were sticky, smelly, drippy and took a long time to dry.  However, the solvent-based adhesives tended to be better for survival of the label and removability without damaging the artifact.  To put it bluntly, the trade-off is: ease of application for the human comes at the cost of optimum preservation of the label and artifact.

3. RESULTS

PARALOID B-72 (ACRYLOID B-72)

B72 (marketed as Acryloid or Paraloid B-72) is a solvent-based acrylic resin.  It was tested in both reagent grade acetone and hardware store acetone.

PROS

  • Good aging properties, does not yellow
  • Pure formulation
  • Good durability in flood or high RH
  • Minimal staining after removal
  • Readily reversible with solvent
  • Hardware store acetone less likely to smear inks (likely due to impurities)
  • Reasonably neutral pH around 5-7
  • Paper label alone remains slightly flexible, adhesive film cracks a bit

CONS

  • Not locally available
  • Solvent fumes
  • Flammable
  • Can be sticky, stringy, require practice to apply
  • Acetone can evaporate too quickly to fully manipulate label
  • May bubble unpredictably, with no obvious fix that always works
  • Hardware store acetone results in mottled look
  • Harder to apply on bumpy surfaces than water-based adhesives
  • Label does not always self-position well
  • Corners of label sometimes lifted, risk for snagging
  • Poorer adhesion to wood than other substrates
  • Can cause some inks to smear
  • Cleanup is not as easy as water-based adhesives

B-72 with Soluvar or Regalrez top coat

Because B-72 is such a desirable barrier layer, alternate topcoats were explored to solve the smearing problem.  Soluvar is made of acrylic resins B67 and F10 in petroleum distillates, used as a picture varnish.  Regalrez is similar, but made of low molecular weight resins in petroleum distillate.  While solving the smear issue, the alternate topcoats caused other frustrations.

PROS:

  • Good aging in general
  • Pure formulation
  • Good durability in flood or high RH
  • Minimal staining
  • Readily reversible with solvent
  • Does not make ink smear the way acetone-based B-72 can.
  • Does not bubble
  • Reasonably neutral pH around 5-7
  • Paper label alone remains slightly flexible, adhesive film cracks a bit

CONS:

  • Not locally available
  • Soluvar sometimes leaves drips on surface of artifact after applied
  • Lingering paint-thinner type odor
  • Flammable
  • Top coat makes paper translucent or mottled, hard to read on dark surfaces
  • 2 step application: B-72, dry, then topcoat
  • Soluvar / Regalrez stay sticky for more than 24 hours
  • Soluvar yellowed a bit during artificial aging
  • Corners of label tend to stick up, risk snagging
  • Stickiness of topcoat annoying
  • Cleanup is not as easy as water-based adhesives

At the Cleveland Art Museum, conservator Sam Springer reports that printed labels are first given a coating of Aquazol to prevent the ink from smearing.

At the Alutiiq Museum in Kodiak, Alaska, registrar Marnie Leist reports they use B-72 as a barrier layer and art store acrylic as the topcoat.

ART STORE ACRYLICS

Water-based acrylic media including Daniel Smith Acrylic, Golden Fluid Matte Medium, Golden Gel, Golden Self-Leveling Gel, Liquitex Gloss Medium, Liquitex Matte Medium were tested as examples of art store acrylics.  Golden Gel is used by several museums in Alaska.

PROS

  • Easy application and cleanup
  • Locally available
  • Does not bead up as much as Acrysol WS-24 or Aquazol
  • Tacky, so label stays put when topcoat added
  • Good on bumpy surfaces
  • Does not smear inks
  • Does not bubble
  • Paper label alone remains flexible

CONS

  • High pH (alkaline) Measured from 8 – 10 in our tests
  • Most contain ammonia
  • All can corrode metals, especially copper and Cu alloys (tuned adhesive green)
  • Proprietary (impure formulations, can change anytime)
  • Yellows with age
  • Removal by swelling with solvents, then rubbing off
  • Removal can cause surface loss, since it doesn’t dissolve but swells
  • In flood/ high RH tended to become gummy and white, sometimes peeled off

RHOPLEX

Because water-based adhesives are more user-friendly than the solvent-based adhesives, conservation-grade water-based acrylic adhesive Rhoplex (also marketed as Primal) 33 or its replacement B-60-A was tested as an alternative to B-72 and art store acrylics.  Rhoplex is often used as a stone and plaster consolidant. Note that WS-24 is a different product.

PROS

  • Easy application and cleanup
  • Good on bumpy surfaces
  • Good aging
  • Pure formulation
  • Good durability in flood or high RH
  • Does not smear inks
  • Does not bubble
  • Paper label alone remains flexible

CONS

  • Not locally available
  • Cannot ship in freezing weather (product will be ruined)
  • High pH (very alkaline) Measured around 9-12 in our tests
  • Can corrode metal, adhesive turned yellow-green on aging.
  • Can yellow with age, saw some pink tinting around ink
  • Difficult to remove

ACRYSOL WS-24

Because water-based adhesives are more user-friendly than the solvent-based adhesives, conservation-grade water-based acrylic adhesive Acrysol WS-24 was tested as an alternative to B-72 and art store acrylics.  It is sometimes used as a consolidant for waterlogged archaeological bone.  Note that it is also sometimes sold as Rhoplex  or Primal WS-24.

PROS

  • Easy application and cleanup
  • Good on bumpy surfaces
  • Good aging
  • Pure formulation
  • Does not smear inks
  • Does not bubble
  • Reasonably neutral pH around 6-7

CONS

  • Not locally available
  • Can corrode metal (turned green-brown in aging test)
  • Can be watery when applied and label slips around
  • Yellows with age (more than other adhesive we artifically aged)
  • Weaker bond with age
  • Difficult to remove from porous surfaces
  • Paper label alone is brittle, cracks and shatters easily when flexed

AQUAZOL

Because water-based adhesives are more user-friendly than the solvent-based adhesives, conservation-grade Aquazol (a non-acrylic water based plastic) was tested as an alternative to B-72 and art store acrylics.  It is soluble in either water or alcohol.  It is commonly used as a paintings consolidant.

PROS

  • Easy cleanup
  • Good on bumpy surfaces
  • Good aging
  • Pure formulation
  • Does not smear inks
  • Does not bubble
  • Reasonably neutral pH around 5-7
  • Paper label alone remains flexible

CONS

  • Not locally available
  • Falls off readily in flood test
  • Messy and sticky to handle
  • Gets sticky or falls off in high RH (80%)
  • Corroded metal in some tests (adhesive turned green)
  • Can be watery when applied and label slips around

AYAF

AYAF is marketed pre-mixed as “PVA Marking Varnish” by MuseuM Services Corporation.  AYAF is a solvent-based polyvinyl acetate (PVA) resin equivalent to the European products Mowilith 50 and Vinylite A.  It is most often used as a consolidant for various materials.

PROS

  • Pure formulation
  • Reasonable aging properties (not as ideal as B-72)
  • Does not smear inks
  • Does not bubble
  • Easer to apply than B-72, but with many of its benefits
  • pH 5.5 still in the OK range
  • Paper label alone slightly flexible, does not crack

CONS

  • Not locally available
  • Not as easy to apply and cleanup as water-based adhesives
  • Harder to apply on bumpy surfaces
  • Solvent fumes
  • Peels off easily in flood test

NAIL POLISH

Fingernail polish is still occasionally seen in obsolete museum practices.  It was tested here with expectation for poor performance to gauge other adhesives against a “known negative.”  I tested Sally Hansen “Hard as Nails”

PROS

  • Locally available
  • Easy application and cleanup
  • Does not bubble

CONS

  • Proprietary (impure formulations, can change anytime)
  • Yellows with age
  • Acidic pH of 2-3
  • Strong odor
  • Smears ink
  • Corners of label tend to stick up, risk snagging
  • Paper label cracks, tears when flexed

4. METHODOLOGY

ELLEN CARRLEE (Conservator, Alaska State Museum)

Substrates:

  1. Metal: Penny coins dating after the year 2000, fresh from normal use without pre-cleaning.
  2. Stone: Dark gray slate from a museum diorama.
  3. Ceramic: Plain terracotta flowerpot, had been in outdoor use one summer.
  4. Bone: Mammal, mainly beach finds.
  5. Tooth: Mammal, from the museum educational collection.
  6. Wood: Plain popsicle sticks from craft store.

Adhesives:

B-72 in reagent grade acetone

B-72 in hardware store acetone

B-72 in reagent grade acetone with Soluvar topcoat

B-72 in reagent grade acetone with Regalrez topcoat

“PVA Marking Varnish” (AYAF in alcohol)

Aquazol 500 in ethanol

Daniel Smith Acrylic Medium (at least 10 years old, in the lab supplies)

Rhoplex B-60-A

Acrysol WS-24

Golden Self Leveling Gel

Golden Gel

Sally Hansen “Hard As Nails” nail polish

Abuse:

The tests involved submersion in a vat of water over a weekend (to simulate a flood incident), sealing in a bag at 80%RH for 24 hours, aggressively shake samples of each substrate together in a ziplock bag, aggressive abrasion with a dry toothbrush, and heating in an oven.  pH tested by adding a drop pHydrion pencil in solution to the wet adhesive Insta-check pencil “lead” dissolved in boiled, distilled water (see Odegaard, Carroll, Zimmt 2000).  Strip of pure copper painted with adhesives as a separate test for copper corrosion.  Tested paper label dipped in adhesive alone for durability.

Removal:

Removal techniques tested were dry scalpel removal (also called “mechanical” removal), water on a cotton swab, and acetone on a cotton swab.

ANNA WEISS (conservation graduate student, Queen’s University)

Substrates:

  1. Metal: pennies
  2. Stone: dark, fine grained stones from Lake Ontario beach
  3. Ceramic: terra cotta flowerpot (new)
  4. Bone: study samples from local archaeology group
  5. Wood: blocks of pine lumber

Adhesives:

B-72 in reagent grade acetone

B-72 in hardware store acetone

B-72 in hardware store acetone with Soluvar topcoat

Aquazol 500 in water

Rhoplex 33 (aka Primal)

Aquazol WS-24

Liquitex Acrylic Gloss Medium and Varnish

Liquitex Matte Medium

Abuse:

The tests involved submersion in a vat of water for two hours (to simulate a flood incident), sealing in a bag at 80%RH for 72 hours, aggressively shake samples of each substrate together in a ziplock bag, aggressive abrasion with a dry toothbrush, accelerated aging in over for 4 days to simulate 12 years, pH testing with pH strips using dried label mashed in water.

Removal:

Solvent removal with cotton swab, poultice or solvent gel, mechanical removal with scalpel, bamboo stick or dental tool.

SAMANTHA SPRINGER (Assistant Conservator of Objects, Cleveland Museum of Art)

Substrates:

  1. Metal: brass sheet
  2. Stone: smooth fine grained stones from museum campus
  3. Ceramic: terra cotta flowerpot (new)
  4. Glass: pyrex glassware
  5. Wood: pine 2 x 4 scrap wood

Adhesives:

B-72 in reagent grade acetone using Aquazol-coated label

Golden Polymer Medium Gloss

Aquazol 500 in water with B-72 topcoat

Rhoplex WS-24 Acrylic Dispersion (sprayed, reactivated with isopropanol)

B-67 in reagent grade Naptha (petroleum distillate)

B-67 in reagent grade Naptha using Aquazol-coated label

B-67 in acetone using Aquazol-coated label.

For some tests, the “Aquazol-coated label” was first spray-coated with two coats of 12% Aquazol 200 in reagent grade ethanol and allowed to dry.  This is to prevent smearing of the ink.

Abuse:

The tests involved submersion in a vat of water for two hours (to simulate a flood incident), sealing in a bag at 80%RH for 72 hours, aggressively shake samples of each substrate together in a ziplock bag, aggressive abrasion with a dry toothbrush, accelerated aging in over for 4 days to simulate 12 years

Removal:

Solvent removal with cotton swab, poultice or solvent gel, mechanical removal with scalpel, bamboo stick or dental tool.

5. THANK YOU!

Big thanks to our Alaskan museum colleagues and to the folks who discussed this with us on the American Institute for Conservation Objects Specialty listserve.  Apologies if I miss your name, but here’s my best shot: Helen Alten, Barbara Applebaum, Victoria Book, Scott Carrlee, Chris del Re, Dave Harvey, Katie Holbrow, Rick Kerschner, Steve Koob, Marnie Leist, Susan Lansing Maish, Katie Myers, Teresa Myers, Steven Pickman, Dennis Piechota, Monty Rogers, Linda Roundhill, Patrick Saltonstall, Monica Shah, Tony Sigel, Julie Unruh, and Jim Whitney.

Questions? Ideas? Feedback?  Ellen.Carrlee@alaska.gov

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4 Responses to Collections Labeling: Alternate Adhesive Testing

  1. Fantastic, very useful. I will send the link to my students. I get them to carry out a similar exercise sticking different materials.
    I was intrested by your comment on Rhoplex not performing well in the cold. I am hoping to carry out some work with the Antarctic heritage trust on the performance of adhesives and coatings in extremes. I got hooked on cold climate conservation when I was down on the ice for a summer. I am pondering a publication and research on conservation in extremes. Keep up the excellent work.
    All the best ,John

  2. ellencarrlee says:

    Thanks for the kind words! Certainly our little experiments are not the end word, just an addition to the info out there. If you find out more about adhesives in cold conditions, I’d love to hear more. Maybe your students might like the share the results of their testing? Hope you decide to publish your work, too…best wishes,
    ellen

  3. I am going to forward your post to Amy Davidson who is a fossil preparator at AMNH. She and conservator Samantha Alderson did a terrific poster on labeling and marking of fossil specimens that you might find useful for future workshops.
    http://www.vertpaleo.org/AM/documents/Davidson_et_al_2006.pdf

  4. mollyglee says:

    Wow-great work, Ellen, Samantha and Anna! Thank you for sharing all of this valuable information. A group of CA-based conservators (myself included) did a few labeling lectures/practicals last year-at a museums conference at an archaeology conference-which definitely gave me a better appreciation for the challenges and the issues you’ve raised here. Any of the systems described here require some practice first! A couple things that we experimented with were mixing B-72 in an 80/20 acetone/ethanol mixture-we found that the ETOH helped to decrease bubbling and stringiness. We also tried dipping the printed paper labels in the B-72 solution and adhering them directly to objects that way, which sometimes worked well.
    This is a great resource that I’ll be sure to refer to, and refer others to, in the future.

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