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Thanks to all who responded to my initial question. The posts have been interesting, even if they didn't actually answer my question... I'm sure lots of folks would like to know more about these consolidants and adhesives. Since I have no practical experience with many of these products, I have been researching them all in the literature, on list-proc archives, and on the Web. Here's what I've come up with so far (please let me know of any errors you find): The "gold standard" of hardeners, to which everything else is compared, is Butvar 76, a polyvinyl butyral (PVB) resin made by Monsanto. Acryloid B72 is an acrylic resin similar to Butvar. Both are soluble in acetone or ethyl alcohol. Recipes I've seen include one tablespoon of Butvar to 16 oz. of acetone, 4 oz. Butvar per gallon acetone, and a 1:1 ratio of Acryloid B-72 to acetone. A 1:1 ratio should give you a pretty thick glue. One drawback of these products is that it can take a LOT of shaking/stirring/patience to get the beads dissolved. Butvar 76 and Acryloid B72 are highly recommended because they are easily reversible and show long-term integrity. They are also relatively inexpensive. According to (possibly outdated) Websites, Butvar is sold by the Florida Paleontological Society (at the FlaMNH) for $7.50 a lb (plus $15 membership!), and at PaleoBooks for $10 a 1-lb bag. Acryloid B-72 is sold by Conservation Resources Internat'l (www.conservationresources.com) for $35 per kg. One to two pounds should last a long time! Unfortunately, the acetone-based adhesives won't work well on damp materials. For wet stuff, a PVA (polyvinyl acetate) adhesive like Vinac B-15 is recommended. These can dissolved later with acetone or ethanol. PVAs are also pretty cheap. The Black Hills Institute sells it at $8 for a pint/400 grams (will make 4-10 liters of solution), and Uncommon Conglomerates sells it for about $9 a pound. Beware of watered-down Elmer's glue (also a PVA), though, as its ingredients are a trade secret (a problem with any "over-the-counter" product). Much controversy swirls over whether PVAs are as good as, or even better than Butvar. While many folks swear by PVAs, others suggest that they become hard to reverse as the glue ages, produce acids, and get soft at relatively low temperatures. The anti-PVA camp recommends drying the specimens thoroughly and use Butvar instead, if at all possible. A third option is PaleoBond, an adhesive glue and space-filler manufactured by Uncommon Conglomerates, Inc. It is a cyanoacrylate, that is, a superglue, so it is very strong and has been reported to be long-lasting. The very viscous "Jurassic Gel" is particularly useful for filling in larger cracks. However, in my informal survey of opinions, most conservators viewed PaleoBond as non-reversible, or reversible only with much difficulty and possible damage to the specimen. Also, PaleoBond may require the use of an activator that starts a chemical reaction in the material. Some have reported that this reaction can run out of control and actually "explode" the specimen. Others hotly contest these opinions, though. PaleoBond is fairly expensive ($50 for 16-oz bottle of PaleoBond, $36 for 200 grams of Jurassic Gel, plus $10.50 for the activator, and $5.50 for each ounce of "debonder", as sold by the Black Hills Institute). And, as with all superglues, you're bound to glue a few fingers together, so if you use PaleoBond, be sure you have sufficient debonder at the ready to de-stick yourself! We shouldn't forget the most important point: regardless of the hardener or adhesive you use, only treat specimens if absolutely necessary. If the fossil is in good shape, don't mess with it! With all that said, the one piece of information I have not been able to find out is whether Acryloid B72 is considered inferior to Butvar 76, or if they are truly equivalent...so let me ask again...anyone know? Peg Peg Yacobucci Assistant Professor Bowling Green State University Department of Geology 190 Overman Hall Bowling Green, OH 43403 (419) 372-7982
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