Mammoth Tooth

[Ptychodus04]

One of my regular clients picked up this mammoth tooth at an estate sale. The previous owner was kind enough to slather it with plaster and coat that with lacquer around 40 years ago. The tooth was clearly fragile but they didn’t do it any favors. It took a bunch of scribe work and abrasive to remove it all. Then it got a healthy dose of Paraloid to stabilize what cementum was left.

 

 

[Randyw]

Looks much better!

[RJB]

Amazing what some people will do to 'protect' a fossil.   I wasn't any better.  When I first started out I put resin on big scallops I would find. 

 

RB

[Ptychodus04]

1 hour ago, RJB said:

Amazing what some people will do to 'protect' a fossil.   I wasn't any better.  When I first started out I put resin on big scallops I would find. 

 

RB

Yep. Once upon a time, I put lacquer on everything. I learned about conservation Grady polymers pretty quickly though. 

[fossilhunter21]

It looks a lot better than it did! I am not sure why you would apply plaster directly to a fossil like that... I guess it works... 

 

-Micah

 

[Harry Pristis]

1 hour ago, fossilhunter21 said:

It looks a lot better than it did! I am not sure why you would apply plaster directly to a fossil like that... I guess it works... 

-Micah

Maybe the plaster was the result of a naive understanding of "plaster jacket."  

[fossilhunter21]

40 minutes ago, Harry Pristis said:

Maybe the plaster was the result of a naive understanding of "plaster jacket."  

True.  I could definitely see someone (especially 40 years ago, when information was not so easily accessed) trying to jacket a fossil, and not even knowing what they are doing at all. Nowdays you can watch videos about it, and at least mostly be able to do it correctly. 

 

Thanks, 

 

-Micah

[Josesaurus rex]

13 hours ago, Ptychodus04 said:

Yep. Once upon a time, I put lacquer on everything. I learned about conservation Grady polymers pretty quickly though. 

Currently I put polyurethane lacquer on some fossils, only mollusks and somewhat fragile fish bones. Will what I am doing be fine or is it not advisable to use that type of lacquer? 

[Harry Pristis]

 

Polyurethane will not give the desired penetration of the fossil. This resin is very difficult to remove. Putting polyurethane on a fossil is usually a bad idea.

  A much better material for fossils is a polyvinyl butyral plastic such as Butvar B-76 which has become easier to find in small quantities. I have used this plastic, dissolved in acetone, for many types of fossils. (I have used it successfully on Silurian-age shales with brachiopods, for example.) It penetrates well, and in the proper dilution it produces a "damp-looking" finish with no gloss.

[Ptychodus04]

7 hours ago, Josesaurus rex said:

Currently I put polyurethane lacquer on some fossils, only mollusks and somewhat fragile fish bones. Will what I am doing be fine or is it not advisable to use that type of lacquer? 

What @Harry Pristis said. I use Paraloid B72 rather than Butvar B76 but the benefits and process are the same.

[Josesaurus rex]

@harry pristis @Ptychodus04 Well thank you very much then. I will try to get some of those materials to proceed in that way. When I get home I will show you that fish vertebra to which I applied lacquer. I really did it because it was falling apart fast and it was what I had at hand to stop that. 

[Josesaurus rex]

@harry pristis @Ptychodus04

These are the fossils to which I had to apply polyurethane lacquer. 

 

As you can see they had a lot of cracks and there was no choice. 

[Harry Pristis]

 Butvar B-76 and other suitable plastics, such as Vinac, are more frequently available on the Internet these days. But, if you can't find Butvar B-76 or Vinac, you may want to fall back on a solution of Duco Cement (clear, model airplane glue, nitro-cellulose) in acetone. Duco nitro-cellulose is not a first choice, or even a second; but, it will hold a fossil together while you consider other options.

Dilution? Start with a tube of glue dissolved in about five or six ounces of acetone in a glass jar with a metal screw-top. Shake well.

(From this point, the techniques are the same for any plastic consolidant you choose.) Adjust the dilution with more acetone until, after shaking, the tiniest air bubbles are just slightly retarded in their rise to the surface.

[Ptychodus04]

I understand the dilemma you were in. It helps to have proper materials on hand so you’re not in a position to need to turn to lesser desired products. It’s all a learning process. You can usually find Butvar B76 or Paraloid B72 pretty easily online. Vinac (PVA B-15) is no longer manufactured and is much harder to come by but B76 and B72 are better products anyway. Vinac gets soft at temps over 90F where the others need a higher temp to soften.

[Josesaurus rex]

Thank you both very much. I will take the advice I have been given, and I will get butvar or paraloid. There are not many distributors in Chile, so I will see if I order it abroad.