Wrangellian Posted February 19, 2018 Share Posted February 19, 2018 The current question about shellac reminded me to ask about this. I used to use white glue (WeldBond) for all my fossil stabilizing/reassembly. Lately I've noticed that a few of my older shale pieces from my local mountain collected 8-10 years ago with cracks/joints that were repaired/stabilized seem to have slightly wider gaps than I recall them having. I'm not sure whether the glue is slightly swelling or I was just more sloppy back then as to how tight I allowed a joint to be. Could be either, but I hope the latter. I know that white glue will sort of reconstitute when you get it wet, turning white again and swelling slightly, but I don't know if it will expand noticeably with simple atmospheric moisture. These have been kept indoors all this time and we are not known for being as humid as the Southern states for instance. Has anyone else who has used white glue noticed anything like this? I don't want to hear any "don't use white glue, use Paraloid instead", I only want to know whether white glue will swell from moderate humidity. I've been using B-72 lately, but most of my Tzuhalem collection from the past 10 years has white glue in it, and the vast majority of it, including most earlier specimens, show no glue alteration of any sort. Just those few pieces seem to have larger gaps than I'd like. (I know that some people have said white glue will turn yellowish over time but I haven't noticed anything like this yet. Also, I'm not sure that all white glues are the same - I gather Elmer's and the like are made from animal parts, or were formerly, but I don't think WeldBond is.) Link to comment Share on other sites More sharing options...
Manticocerasman Posted February 19, 2018 Share Posted February 19, 2018 I know that if the glue gets wet it is getting malleable. But under normal atmospheric circumstances the glue should not alterate. growing old is mandatory but growing up is optional. Link to comment Share on other sites More sharing options...
ynot Posted February 19, 2018 Share Posted February 19, 2018 I would think that if the majority of Your glued pieces show no separation, then the few that do show seperation have been that way since they were done. Your more practiced eye for prepping just makes the ones with separation stand out now. Link to comment Share on other sites More sharing options...
Wrangellian Posted February 20, 2018 Author Share Posted February 20, 2018 I hope you guys are right! Thanks. Link to comment Share on other sites More sharing options...
caldigger Posted February 20, 2018 Share Posted February 20, 2018 Just a tad off subject, if using a product called "Gorilla Glue", it does swell when curing and will separate your parts unless securely clamped. I have not used this personally, but have heard the horror stories of pushing pieces apart and then having an incredibly strong bond, not easy to go back and remedy. 1 Link to comment Share on other sites More sharing options...
Bullsnake Posted February 20, 2018 Share Posted February 20, 2018 1 hour ago, caldigger said: Just a tad off subject, if using a product called "Gorilla Glue", it does swell when curing and will separate your parts unless securely clamped. I have not used this personally, but have heard the horror stories of pushing pieces apart and then having an incredibly strong bond, not easy to go back and remedy. I'll vouch for that from repairing a pair of my reading glasses. I don't think use on fossils would be recommended at all. 1 Steve Link to comment Share on other sites More sharing options...
Wrangellian Posted February 21, 2018 Author Share Posted February 21, 2018 BY the sound of it, Gorilla Glue is meant for things that have a gap that won't close tightly but you want to seal it anyway... like in wall or something. 1 Link to comment Share on other sites More sharing options...
Wrangellian Posted May 17, 2019 Author Share Posted May 17, 2019 (Can't believe it was that long ago that I first started this topic) I heard back from one of the assistant curators at the RBCM who asked their conservator(s) about white glue. Here's the reply: Wel Bond is a PVA (a water based adhesive). It is dissolvable in water but does not swell, at least not with the amount of moister even a high (above 65% RH) humidity environment would provide. It is more likely that if the fossils were held in a high humidity environment for a long period of time that the moisture in the air could slowly breakdown some of the bonds in the glue. This is sort of a theoretical possibility I haven’t seen any specific information on it but it could make sense. PVA can also be dissolved by solvents like acetone. If they the fossils were stored near solvents, off gassing from those could also slowly break the bonds in the glue.” It's a little reassuring, but the question still remains what happened to some of my specimens. I hope it was just sloppiness, but there has certainly been some degradation/disintegration in my specimens here and there - and last night I discovered an extreme example: a small ammonite that has been in a drawer for a few years has apparently pushed itself apart from the inside, as if something like pyrite inside it has gone thru a chemical reaction and expanded. There was white glue added to stabilize it soon after I brought it home, but it has not withstood the expansion. I'll post pics soon. Link to comment Share on other sites More sharing options...
caldigger Posted May 17, 2019 Share Posted May 17, 2019 On 2/20/2018 at 4:56 PM, Wrangellian said: BY the sound of it, Gorilla Glue is meant for things that have a gap that won't close tightly but you want to seal it anyway... like in wall or something. The theory behind this glue is it needs to be tightly clamped. It "swells/expands into the pores of the item being glued therefore assuring a very durable bond. Link to comment Share on other sites More sharing options...
jpc Posted May 17, 2019 Share Posted May 17, 2019 On 2/18/2018 at 10:19 PM, Wrangellian said: (I know that some people have said white glue will turn yellowish over time but I haven't noticed anything like this yet. Also, I'm not sure that all white glues are the same - I gather Elmer's and the like are made from animal parts, or were formerly, but I don't think WeldBond is.) you might have hit the nail on the head here without even swinging a hammer. One of the issues with commercial products is that we never know what is in them. Could be that they changed the formula for a while and the change is what you sre seeing now decades later. They can change the formula and no one would ever know. I'm just saying MAYBE. I do not know the actual answer to your question. Link to comment Share on other sites More sharing options...
Wrangellian Posted May 17, 2019 Author Share Posted May 17, 2019 I've wondered the same thing, but as you say, no way to check. In any case it should be some sort of PVA solution, right? I don't really know my chemistry, like how many variations or additives are there to PVA glues. Anyway the conservationist's reply seems reassuring. All of the fossils in question were collected over the last 10 years and have been kept in the same room, and most have WeldBond (hundreds), and most of these have stayed good and tight, including many from the early days, and I would think if the glue was swelling up with humidity, they would all have these problems, but only a few do. Link to comment Share on other sites More sharing options...
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