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Can PMMA be used as a substitute to Paraloid?


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I am quite new to preparing and preserving fossils and am not very knowledgeable on resin coatings.

I have been told that Poly Methyl Methacrylate has some similar properties to Paraloid and can be dissolved and used to coat fossils.

Is there a reason it is not used for this purpose?

Thank you very much for the info.

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Personally I use Vinac (from an old stock) Butvar 44  Butvar 72 and Butvar 76. as all of these have long histories of being used for fossils and do not seem to yellow over time. They are also quite reversible when used as a glue. 

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10 minutes ago, Malcolmt said:

Personally I use Vinac (from an old stock) Butvar 44  Butvar 72 and Butvar 76. as all of these have long histories of being used for fossils and do not seem to yellow over time. They are also quite reversible when used as a glue. 

Where do you buy Butvar?

I have seen some Paraloid on the auction site but not much Butvar the only one listing I saw did not have a number associated with it and was just called polyvinyl butyral not sure if that would be safe to use with the fossils.

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Ptychodus04
1 hour ago, Misha said:

Where do you buy Butvar?

I have seen some Paraloid on the auction site but not much Butvar the only one listing I saw did not have a number associated with it and was just called polyvinyl butyral not sure if that would be safe to use with the fossils.

You can buy Butvar B76 HERE. It is quite a bit more expensive than Paraloid B72. I just ordered my first bit of Paraloid as I am almost out of my stock of Vinac. Paraloid B72 is the preferred consolidation material for most projects at the AMNH (per Goldberg and Davidson 2014)

 

Butvar B76 and Paraloid B72 are very similar. Butvar B98 is an oddball as it is insoluble in Acetone. It requires ethyl alcohol as a solvent which causes it to set slower and has a less glossy finish.

 

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I purchased mine from Black Hills Institute but I do not believe they sell any more as they now sell premade Paleobond products

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1 hour ago, Ptychodus04 said:

Butvar B76 and Paraloid B72 are very similar. Butvar B98 is an oddball as it is insoluble in Acetone. It requires ethyl alcohol as a solvent which causes it to set slower and has a less glossy finish

What concentrations would you recommend to use them in?

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Mark Kmiecik
6 hours ago, Misha said:

I am quite new to preparing and preserving fossils and am not very knowledgeable on resin coatings.

I have been told that Poly Methyl Methacrylate has some similar properties to Paraloid and can be dissolved and used to coat fossils.

Is there a reason it is not used for this purpose?

Thank you very much for the info.

You know that Poly Methyl Methacrylate is commonly called Plexiglas, right? If you research the properties of Plexiglas you can compare its characteristics to those of other materials and decide which has the properties you deem most desirable for the specimen in question. There is no right or wrong -- only more suitable for the given circumstances. In all cases, the less intrusively you can achieve the desired results, the better. Less is more.

 

Personally, though I have never used it, I would imagine that it would tend to "pool" more because of its molecular structure creating an "extremely wet" appearance, and also because of the solvents used, di- and trichloromethane (chloroform) I would opt for something else.

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10 hours ago, Malcolmt said:

Butvar 76.

What concentration of it do use when coating your fossils?

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I actually rarely coat. I am a bit of a purest on my own fossils. I only use it when the fossil needs it for consolidation. If the prep is for someone else I generally ask them what their preference is.

 

Not super precise but about 5%. Quite thin crystal clear so when the acetone  evaporates it is a super thin film

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18 minutes ago, Malcolmt said:

I actually rarely coat. I am a bit of a purest on my own fossils. I only use it when the fossil needs it for consolidation. If the prep is for someone else I generally ask them what their preference is.

 

Not super precise but about 5%. Quite thin crystal clear so when the acetone  evaporates it is a super thin film

I'm with Malcomt on this one... rarely ever is there a need to coat a fossil.  

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Ptychodus04

I only coat when the fossil needs to be stabilized to keep it from falling apart. Often, fish require some stabilization as their bones tend to flake.

 

I measure my solution 1 part plastic to 50 parts acetone by weight or volume. As @Malcolmt said, it’s not exact, you just need something that has a very low viscosity to allow it to soak in.

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Mark Kmiecik

And please be aware that inhaling acetone fumes will eventually kill you.

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Ptychodus04
12 hours ago, Mark Kmiecik said:

And please be aware that inhaling acetone fumes will eventually kill you.

 

IMHO, definitely not medical advice...

 

Hobbyist exposure to acetone is rather innocuous if done properly. Getting it on your skin gives you a significantly higher dose than breathing limited vapors. If you are going to be working with it often, you should take measures to prevent skin exposure (and wear a respirator) as it is a general solvent which is easily absorbed into the body and can dissolve the cell membrane.

 

That being said, when prepping, it’s not one’s biggest concern. Dust is far more concerning as the preparator is exposed to it on a far more regular occurrence. Lung protection comes in here as well. A quality respirator is a must.

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Mark Kmiecik
8 hours ago, Ptychodus04 said:

 

IMHO, definitely not medical advice...

 

Hobbyist exposure to acetone is rather innocuous if done properly. Getting it on your skin gives you a significantly higher dose than breathing limited vapors. If you are going to be working with it often, you should take measures to prevent skin exposure (and wear a respirator) as it is a general solvent which is easily absorbed into the body and can dissolve the cell membrane.

 

That being said, when prepping, it’s not one’s biggest concern. Dust is far more concerning as the preparator is exposed to it on a far more regular occurrence. Lung protection comes in here as well. A quality respirator is a must.

I'm old and back in the day acetone was considered 'toxic', and I didn't believe what Ptychodus said, so I just did some research. Lo and behold, it was removed from the list of toxic chemicals in 1995, and nobody told me. The wikipedia info says that it is only mildly harmful if breathed or ingested or brought into contact with the skin. So many of the things that were once established 'facts' are being blown out of the water in recent times it makes me question everything I learned.

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Ptychodus04
7 hours ago, Mark Kmiecik said:

So many of the things that were once established 'facts' are being blown out of the water in recent times it makes me question everything I learned.

 

It’s always good to question everything you’ve learned. :zzzzscratchchin:

 

I’ve grown a lot by doing that regularly.

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7 hours ago, Mark Kmiecik said:

So many of the things that were once established 'facts' are being blown out of the water in recent times it makes me question everything I learned.

Yes, definitely.

While working with my 3d printed parts I was once told that acetone is a carcinogen, but a quick Google search disproved that idea.

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DPS Ammonite

I use acetone with my Butvar B76. I use it in well ventilated areas because of the smell. Keep ignition sources away since acetone is very flammable. You do not want to combust.

 

While doing online research on the hazards of acetone, I came across an article that suggested that human metabolism could produce too much acetone that could lead to spontaneous combustion. 

 

https://www.realclearscience.com/blog/2012/12/how-to-avoid-spontaneously-combusting.html

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