Adhesives and Consolidants
Selecting the most appropriate adhesive for the task at hand, whether joining, consolidating or coating a specimen, is an important part of successful fossil preparation.
The key to making a suitable selection is to understand that not all of these adhesives are interchangeable — some are more appropriate for particular tasks than others.
There is no single adhesive that works best in every preparation situation. Understanding the distinctions between them helps to explain differences in both their working and final properties. The adhesives that preparators use can be divided into two basic categories according to how they set or dry:
Solution adhesives which set by evaporation of a solvent and include:
- Paraloid B-72 (ethyl methacrylate co-polymer, formerly called Acryloid)
- Butvar B-76 (polyvinyl butyral, or PVB)
- Butvar B-98 (polyvinyl butyral or PVB)
- McGean B-15 (polyvinyl acetate or PVAC, formerly called Vinac B-15)
- “White glue” dispersions and emulsions (e.g. Elmers, Rhoplex, Lascaux)
Reaction adhesives, which set by chemical reaction and include:
- Various brands of epoxies (e.g. Devcon, Epo-Tek)
- Various brands of cyanoacrylates (e.g. Aron Alpha, Paleo-bond)
With this collection of adhesives, preparators are able to perform a multitude of tasks including joining, consolidation, coating, and gap filling on a range of fossils which can differ greatly in size and state of preservation. Read more about the properties of solution and reaction adhesives by clicking here.
The long history of fossil preparation has meant that a wide variety of adhesives and consolidants have been used in the past. While some of these some are still available, many on the list below are much older materials and the following are adhesives not recommended for use in preparation: (Shelton and Chaney, 1994):
- Duco cement
- Elmer’s glue-all
- Five minute epoxy
- Cellulose Nitrate polymers (e.g. Glyptal)
- Model airplane glue
- Natural organic materials
- Gum arabic
- Animal protein glues
These products show poor ageing and, in some cases, working properties. Given the other choices now available to preparators there is little reason for any of these materials to be used at this time. Click here to obtain more information on specific issues relating to adhesives and fossil preparation.
The bulk of the text on this and the other pages on this topic was excerpted and adapted from An Introduction To Solution And Reaction Adhesives For Fossil Preparation by Amy Davidson and Samantha Alderson published in Methods in Fossil Preparation Proceedings of the First Annual Fossil Preparation and Collections Symposium, edited by Matthew A. Brown, John F. Kane, and William G. Parker. Petrified Forest, 2009. To read the complete text and access the specific citations download the full article. To learn more about the other talks given at the symposium visit the National Park Service Petrified Forest Fossil Preparation and Collections Symposium page. Click here to buy a copy of the published proceedings.
Download the document Adhesives and Adhesion by Jonathan Thornton, a professor in the conservation program at Buffalo State College. This document covers topics including:
History, Terminology, Choice of Adhesive, and gives information on a wide range of specific adhesives used in conservation.
Adhesives and consolidants in geological and paleontological applications; part one: introduction, guide, health and safety, definitions and part two: wall chart. Society for the Preservation of Natural History Collections. 1997. vol 1 leaflet 2. By Ann Elder, Scott Madsen, Gregory Brown, Carrie Herbel, Chris Collins, Sarah Whelan, Cathy Wenz, Samantha Alderson and Lisa Kronthal.
Learn more in the distance learning course Chemistry for Conservators. This course, taught by Velson Horie a leading expert in the field, is available through International Academic Projects. Download Horie’s useful Adhesives glossary here.
Read a case study by AMNH preparator Amy Davidson on The use of cyanoacrylates and Butvar B-76 (polyvinyl butyral) on a specimen of Shuvuuia deserti (IGM 100/977)
from Ukhaa Tolgod, Gobi Desert, Mongoliaabout and download the associated handout.
Read more about why 5-minute epoxy might not be the best choice for use in fossil preparation….
The references listed below are those that were used in the research for this page. For additional references on this topic see the Bibliography in the Tools and Resources section of this site.
Chiantore, O and M. Lazzari. 2001. Photo-oxidative stability of Paraloid acrylic protective polymers. Polymer 42 (1): 17-27.
Domaslowski, W. 1987-88. The mechanism of polymer migration in porous stones. Weiner Berichte uber Naturwissenschaft in Kunst 4/5: 402-425.
Down, J. L. 1984. The yellowing of epoxy resin adhesives: report on natural dark aging. Studies in Conservation 29: 63-76. Abstract accessible online on the IIC website Studies in Conservation page.
Down, J.L. 1986. The yellowing of epoxy resin adhesives: report on high intensity light aging. Studies in Conservation 31: 159-170. Abstract accessible online on the IIC website Studies in Conservation page.
Down, J.L. 2001a. A literature review of cyanoacrylate adhesives. Reviews in Conservation 2: 35-38. Abstract accessible online on the IIC website Studies in Conservation page.
Down, J.L. 2001b. Review of CCI research on epoxy resin adhesives for glass conservation. Reviews in Conservation 2: 39-46. Abstract accessible online on the IIC website Studies in Conservation page.
Down, J.L. and E. Kaminska. 2006. A preliminary study of the degradation of cyanoacrylate adhesives in the presence and absence of fossil material. Journal of Vertebrate Paleontology 26(3): 519-525.
Down, J.L. et al. 1996. Adhesive testing at the Canadian Conservation Institute: an evaluation of selected poly(vinyl acetate) and acrylic adhesives. Studies in Conservation 41 (1): 19-44. Abstract accessible online on the IIC website Studies in Conservation page.
Feller, R.L. and M. Curran. 1975. Changes in solubility and removability of varnish resins with age. Bulletin of the American Institute for Conservation of Historic and Artistic Works 15 (2): 17-26.
Feller, R.L. et al. 2007. Photochemical deterioration of poly(vinylbutyral) in the range of wavelengths from middle ultraviolet to the visible. Polymer Degradation and Stability 92 (5): 920-931.
Hansen, E.F. et al. 1993. Consolidation of porous paint in a vapor-saturated atmosphere: A technique for minimizing changes in the appearance of powdering, matte paint. Journal of the American Institute for Conservation 32: 1-14.
Horie, C. V. 1987. Materials for conservation. London: Butterworths.
Howie, F.M.P. 1984. Materials used for conserving fossil specimens since 1930; a review. In: Bromelle, N.S., Pye, E.M., Smith, P., and Thompson, G. (eds.), Adhesives and Consolidants, Preprints of the Contributions to the Paris Congress, IIC: 92-8.
Johnson, J.S. 1994. Consolidation of archaeological bone: a conservation perspective. Journal of Field Archaeology 21(2): 221-233.
Koob, S.P. 1982. The instability of cellulose nitrate adhesives. The Conservator 6: 31-34.
Koob, S. P. 1986. The use of Paraloid B-72 as an adhesive: Its application for archaeological ceramics and other materials. Studies in Conservation 31: 7-14.
Lazzari, M., and O. Chiantore. 2000. Thermal-ageing of Paraloid acrylic protective polymers. Polymer 41 (17): 6447-6455.
Podany, J. et al. 2001. Paraloid B-72 as a structural adhesive and as a barrier within structural adhesive bonds: evaluations of strength and reversibility. Journal of the American Institute for Conservation 40(1): 15-33.
Rixon, A.E. Fossil Animal Remains: their preparation and conservation,1976.
Wilks, H. series ed. 1987a. Science for Conservators. Book 1: An Introduction to Materials. London: Museums & Galleries Commission.
Wilks, H. series ed. 1987b. Science for Conservators. Book 2 :Cleaning. London: Museums & Galleries Commission.
Wilks, H. series ed. 1987c. Science for Conservators. Book 3: Adhesives and
Coatings. London: Museums & Galleries Commission.