Giant Beaver Molar Peeling

[historianmichael]

I recently purchased a pack of gravel from Florida filled with Miocene and Pleistocene fossils. Among the fossils was a giant beaver molar. I rinsed it off with water, left it to dry and came back to find that has started to peel. Has this happened to anyone before? How would you recommend consolidating the tooth so that it stops peeling? I have tried to use Butvar before but I have never seemed to get the right ratio to protect the fossil while avoiding the shine. Would you recommend dunking the entire tooth in the solution or to apply some using a dropper or paint brush? Any help would be greatly appreciated. 

 

[Ptychodus04]

If you have Butvar, you can remove the sheen by lightly rubbing the surface after consolidation with a cloth soaked in acetone. This removes the topmost layer of plastic without compromising the consolidation. I like a solution of 1 part plastic to 50 parts solvent by weight for consolidation. This provides a good level of consolidation. Heat the fossil with a heat gun or in a warm oven to ensure all water is gone. Then soak the fossil in the solution until it stops releasing bubbles. Allow to dry on a cardboard flat or egg carton.

 

It is peeling because of the application of water to the already dry fossil. This sets up a condition where differential drying damages the specimen. The surface dries faster than the core and the slight contraction on the surface creates a stress that cracks the specimen. You can avoid this by washing your specimen in ethanol or acetone to remove soils rather than in water.

[historianmichael]

Thanks @Ptychodus04! I did not know about the issue with water. I will have to be much more careful going forward. Do you know if this only happens with certain types of fossils?

 

I read on here recommendations for a 5% weight/volume ratio for B76 and acetone. Do you recommend something else for fixing this type of problem?

 

[Ptychodus04]

59 minutes ago, historianmichael said:

Thanks @Ptychodus04! I did not know about the issue with water. I will have to be much more careful going forward. Do you know if this only happens with certain types of fossils?

 

I read on here recommendations for a 5% weight/volume ratio for B76 and acetone. Do you recommend something else for fixing this type of problem?

 

5% gives you a roughly 20:1 ratio. Personally, I find that to be good for consolidating porous bone but too thick for things like cracked teeth. It's really a personal preference. Many fossils will suffer from damage when drying. Vertebrate fossils tend to suffer more then invertebrates due to the porosity of their structures. Also, more recent fossils tend towards a more severe effect due to their lower level of mineralization. Pleistocene fossils tend to completely break apart, sometimes violently.

 

Slow drying helps to prevent this. You want to control the surface moisture so it doesn't dry faster than the interior. This is why acetone is a good choice for removing soils. It evaporates easily from the interior of the fossil.

[historianmichael]

31 minutes ago, Ptychodus04 said:

5% gives you a roughly 20:1 ratio. Personally, I find that to be good for consolidating porous bone but too thick for things like cracked teeth. It's really a personal preference. Many fossils will suffer from damage when drying. Vertebrate fossils tend to suffer more then invertebrates due to the porosity of their structures. Also, more recent fossils tend towards a more severe effect due to their lower level of mineralization. Pleistocene fossils tend to completely break apart, sometimes violently.

 

Slow drying helps to prevent this. You want to control the surface moisture so it doesn't dry faster than the interior. This is why acetone is a good choice for removing soils. It evaporates easily from the interior of the fossil.

That makes a lot of sense. I now have to worry that I may have damaged the other Pleistocene fossils in the package. None have displayed such a severe reaction yet, but I will have to closely monitor them. Thank you again for the advice. I will mix up a solution at a ratio of about 2g per 100 ml acetone. Hopefully that will do it. Would you recommend this ratio and method (i.e. soaking the fossil in the solution) for other non-bone materials? The package also came with turtle shell pieces, a manatee tooth, alligator osteoderm, and a rodent mandible.

[Ptychodus04]

1 hour ago, historianmichael said:

That makes a lot of sense. I now have to worry that I may have damaged the other Pleistocene fossils in the package. None have displayed such a severe reaction yet, but I will have to closely monitor them. Thank you again for the advice. I will mix up a solution at a ratio of about 2g per 100 ml acetone. Hopefully that will do it. Would you recommend this ratio and method (i.e. soaking the fossil in the solution) for other non-bone materials? The package also came with turtle shell pieces, a manatee tooth, alligator osteoderm, and a rodent mandible.

You can soak anything in that solution, as long as it has not been glued together already. Acetone will dissolve most adhesives to some degree.

[historianmichael]

Thank you @Ptychodus04 for all of your advice. I was able to mix a solution at a 50:1 ratio and I thought it turned out as best as it could. There is a little shine to it but not too bad. I should have turned it vertical while drying as there is a little more shine where the solution kinda pooled. You live and learn. Here is the final result:

 

[Ptychodus04]

Looks good. You can wipe the surface with a Qtip soaked in acetone to remove the surface sheen.