Help!

[AranHao]

Hello,

I have a tyrannosaur tooth, and when I applied it with Paraloid B-72, it looked covered in white. I tried to restore it with acetone, but the white color still existed even after it dried. I guess acetone releases the glue from the teeth?

What should I do now to restore it to its original appearance.

 

original

 

after

[AranHao]

@Ptychodus04Can you help me?

[Ptychodus04]

It looks like you had some moisture involved. Since you're in Hong Kong, I'm going to assume you are dealing with very high humidity in the air. That is likely the culprit. Acetone will dissolve cyanoacrylate glues eventually and it is probable that this tooth is held together with it. That could be compounding your problem.

 

The best way to remove the cloudy glue is with micro-abrasive. Iron powder will take it off without any damage to the tooth but, I'm going to assume you don't have that available to you. Try soaking a Q-tip in acetone and scrub a single spot repeatedly to see if you can get the glue to dissolve on that spot. If it does, you can use that method to slowly remove all of it from the tooth surface. If that doesn't work, you might need professional help. 

[AranHao]

@Ptychodus04 

Thank you for your reply. I do have high humidity here.

After a day, I quickly applied a higher concentration of Paraloid B-72 to it, and the white color that covered it disappeared. It looked pretty good, but I don't know why.

 

 

Edited June 25 by AranHao

[Ptychodus04]

Great. The acetone in the solution dissolved the Paraloid with the trapped moisture. The higher concentration of plastic in the new solution likely slowed the evaporation of the acetone enough to keep moisture from getting trapped.

[AranHao]

1 minute ago, Ptychodus04 said:

Great. The acetone in the solution dissolved the Paraloid with the trapped moisture. The higher concentration of plastic in the new solution likely slowed the evaporation of the acetone enough to keep moisture from getting trapped.

Thank you for your help!

[AranHao]

@Ptychodus04

May I ask, I don't have enough acetone, can I use ethyl acetate to reverse it without harming the fossil?

 

[Ptychodus04]

44 minutes ago, AranHao said:

@Ptychodus04

May I ask, I don't have enough acetone, can I use ethyl acetate to reverse it without harming the fossil?

 

Paraloid B72 is soluble in acetone, ethanol, toluene, and slightly soluble in isopropyl.

[AranHao]

1 hour ago, Ptychodus04 said:

Paraloid B72 is soluble in acetone, ethanol, toluene, and slightly soluble in isopropyl.

Acetone is a controlled material that is not easily obtainable in some countries. The Paraloid B-72 (10:100) I used in preparing this tooth is a directly purchased finished product. 

Considering the future, I would like to know if I can use ethyl acetate if the specimen is reversed? I am concerned that the involvement of ethyl acetate in this process may damage the specimen.

[Ptychodus04]

@AranHao See below 

 

I'm finding some differing information regarding the solubility of Paraloid B72 in different solvents. Some data sheets include ethyl acetate as an acceptable solvent and others do not include it. I've never used ethyl acetate due to the ease of procuring acetone in the US. I found an art conservation supplier who sells a B72 solution using ethyl acetate as the solvent so, it clearly is somewhat compatible.

 

As for its efficacy and "conservability" in paleo uses, that is undetermined. As long as you are using pure ethyl acetate, I don't see where there would be any long-term issues. I found some research comparing the efficacy of ethyl acetate and acetone. The ethyl acetate is not as strong of a solvent so, dissolution time bay be longer as compared to acetone but it should remove B72 from a specimen.

[AranHao]

4 hours ago, Ptychodus04 said:

I'm finding some differing information regarding the solubility of Paraloid B72 in different solvents. Some data sheets include ethyl acetate as an acceptable solvent and others do not include it. I've never used ethyl acetate due to the ease of procuring acetone in the US. I found an art conservation supplier who sells a B72 solution using ethyl acetate as the solvent so, it clearly is somewhat compatible.

 

As for its efficacy and "conservability" in paleo uses, that is undetermined. As long as you are using pure ethyl acetate, I don't see where there would be any long-term issues. I found some research comparing the efficacy of ethyl acetate and acetone. The ethyl acetate is not as strong of a solvent so, dissolution time bay be longer as compared to acetone but it should remove B72 from a specimen.

Thanks for this info.