ADHESIVES FOR FOSSIL PREPARATION: A MINI-SEMINAR
Amy Davidson
Division of Vertebrate Paleontology
American Museum of Natural History
New York, NY
This one hour seminar will cover basic information about how adhesives work and will have three components:
1) An Adhesives Quiz (WORD 24KB) will be distributed to participants in advance of the Symposium and the answers will be distributed prior to the mini-seminar. This quiz will focus on
four adhesives and two solvents commonly used in fossil preparation: Aron Alpha 201 Cyanoacrylate (Krazy Glue), Devcon 2 Ton Epoxy, Acryloid/Paraloid B72, Butvar B76, acetone and ethanol. Participants will be encouraged to return their completed quiz in advance, as this will help tailor the discussion.
2) Two 15 minute PowerPoint presentations:
ADHESIVES AS LIQUIDS
Adhesives work because they can flow as liquids that then solidify in extremely close contact with the surface to which they are applied. Adhesion of the two solids is due to secondary attractive forces and mechanical interlocking. In their liquid phase and in their setting mechanism, adhesives vary widely but all must be able to flow. Factors that affect flow such as viscosity, wetting and interaction of liquid adhesives with surface contaminants and entrapped air will be discussed, along with techniques to manipulate adhesive flow for the preparation of fossil vertebrates.
FROM LIQUID TO SOLID AND BACK: PHASE CHANGE IN ADHESIVES
All adhesives used in fossil preparation are applied as flowing liquids which set into solids, but through different setting mechanisms. Some solid adhesives can be made to flow again. A basic understanding of phase-change behavior on a molecular level enables the preparator to define the behavior they want for a particular specimen, and to choose the most appropriate adhesive.
This talk will present a basic introduction to solution and reaction setting mechanisms. Gross behavior during phase change such as set time, solvent retention, shrinkage, migration, resolubility and swelling, and the relationship between adhesion and cohesion will be linked to inter and intra-molecular bonding. Specific specimens with different phase-change behavior requirements will be presented as illustrations of the adhesive selection process.
3) Case Studies: The group will look at images of specimens which illustrate common problems. This will be a guided group discussion. Participants will be encouraged in advance of the Symposium to submit images of problem specimens for consideration by the group.
"Adhesives and Adhesion" by Jonathan Thornton (PDF 1.09MB). This excellent general reference paper is written for conservators who use many kinds of adhesives on everything from metal, wood, stone and ivory to leather, paper, painted canvas, photographs, etc. Fossil preparators use relatively few of these adhesives but this paper will give you a good overview and may help you to recognize old adhesives used on fossils in the past.
I recommend two other references:
SPNHC Leaflet #2
Adhesives and Consolidants
in Geological and Paleontological Applications, Spring 1997
Part One: Introduction, Guide, Health and Safety, Definitions
Part Two: Wall chart
This is available from the website for the Society for the Preservation of Natural History Collections (SPNHC)
http://www.spnhc.org/?q=publications/leaflets.html
Science for Conservators
Conservation Science Teaching Series
The Conservation Unit
Vol.1 - Introduction to Materials
Vol.2 - Cleaning
Vol.3 - Adhesives and Coatings
This is available on Amazon.com
These three volumes are an invaluable resource for the conservator and fossil preparator who want to teach themselves basic materials science. The books are clearly and simply written and must be read slowly in sequence from volume one to three. Don't be fooled by the titles. Vol. 2 (Cleaning) includes important concepts such as solubility and Vol. 3 (Adhesives and Coatings) is of little use without the first two.
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