Embedding fossils in resin

[BK1]

I have several thousand shark teeth of every shape and size that I found 25+ years ago that are in storage. If I can ever find them, I’d like to try and embed them in resin and make some kind of desk or coffee table piece, maybe even a river style coffee table with them embedded in the clear resin. For those that have tried it or may have suggestions, what is the best method of sealing the pores in fossils and pyrite to keep them from squeezing out air bubbles during the pressurizing process? I didn’t know if there was a special sealant that folks use.

Thanks

[hadrosauridae]

If you are trying to pour a table top, there is no pressure used.  Best process would probably be to coat them in paraloid first.  When youre ready to pour your surface, pour a thin layer of epoxy, paint the teeth with epoxy and set them into the epoxy base, then pour the remaining epoxy from one spot and let it flow over everything to reduce bubbles.

[BK1]

12 minutes ago, hadrosauridae said:

If you are trying to pour a table top, there is no pressure used.  Best process would probably be to coat them in paraloid first.  When youre ready to pour your surface, pour a thin layer of epoxy, paint the teeth with epoxy and set them into the epoxy base, then pour the remaining epoxy from one spot and let it flow over everything to reduce bubbles.

Thanks, I’ll check out paraloid, I’ve never heard of it. Yea, I don’t have a chamber big enough for tables and cutting boards and such(wish I did!), but I pressurize all my smaller stuff. Looking for something that will preserve the luster and wasn’t sure if just a thin coat of resin or something like Modge-Podge would work. I appreciate the suggestion.

[hadrosauridae]

no, dont put anything like that on the teeth, it will leave a cloudy coating.

[BK1]

9 minutes ago, hadrosauridae said:

no, dont put anything like that on the teeth, it will leave a cloudy coating.

The paraloid? 

[hadrosauridae]

Just now, BK1 said:

The paraloid? 

Paraloid is a clear plastic, it will soak into any pores, cracked, etc that could cause air bubbles in the epoxy.  Stuff like "modge podge" is little more than white elmers glue.  You wont be happy with the results.

[Mark Kmiecik]

53 minutes ago, BK1 said:

I pressurize all my smaller stuff

 

Why do you pressurize it?

[BK1]

51 minutes ago, hadrosauridae said:

Paraloid is a clear plastic, it will soak into any pores, cracked, etc that could cause air bubbles in the epoxy.  Stuff like "modge podge" is little more than white elmers glue.  You wont be happy with the results.

I’ve never had a problem with Modge Podge discoloring anything since it dries clear, but I’ve never used it on a porous surface with a high sheen either. Usually I use it when embedding paper, photographs, and even old records. Most everything else I just do a light sealcoat with resin, but didn’t know if the teeth would hold their glossy look with it…provided the tooth had a shiny gloss to start with. It sounds like the paraloid might be the better choice. Do you have experience with it? If so, does it yellow over time or does it stay clear? Thanks

[BK1]

1 hour ago, Mark Kmiecik said:

 

Why do you pressurize it?

Pressurizing resin squeezes the air bubbles to microscopic size so it make the resin look like clear glass. Without it, the resin would cure with visible air bubbles in it. Anything with very small pores is susceptible to air being slowly squeezed out. Depending on how long it takes the resin you’re using to start getting hard, it may not give the bubbles time to compress before the resin gets too hard for the pressure to do its job. Sometimes those tiny bubbles will be close enough together that they’ll connect and create what looks like a fracture. This hog tooth got sealed on the inside but not the outside. I had no idea that enamel held that much air. I should have sealed the outside of it too, but it’s a good example of what can happen, even with a slow curing resin at 60psi.  

[JohnJ]

Thin 'seal coats' of resin on the object to be embedded will typically prevent any bubbles when it is positioned for the final pour.  Early in the pour, other bubbles can be removed with the careful use of a propane torch.

[BK1]

10 minutes ago, JohnJ said:

Thin 'seal coats' of resin on the object to be embedded will typically prevent any bubbles when it is positioned for the final pour.  Early in the pour, other bubbles can be removed with the careful use of a propane torch.

Right, resin does great for sealing, but I’m not sure how it would alter the look of the tooth. Depending on the texture of the surface, resin can sometimes give the surface of any otherwise shiny object a matted look. Unfortunately, the torch trick only works on surface bubbles. 

[Crusty_Crab]

You seem to have a lot of experience in resin casting. I've always wondered, is there any noticeable difference when you coat an item in 1 substance (i.e. modge podge or paraloid B-72), then embed it into another substance, i.e. epoxy resin. These 2 substances have different refractive indices and does it show in practice or not? I honestly don't know since I haven't tried it myself. BTW, Paraloid/acryloid B-72 is preferred by conservators since it is not known to yellow with age. White glue definitely does. Epoxy resin may also yellow with age.  

[Mark Kmiecik]

I've learned quite a bit here about this process. Thanks for the info, guys.

[BK1]

9 hours ago, Crusty_Crab said:

You seem to have a lot of experience in resin casting. I've always wondered, is there any noticeable difference when you coat an item in 1 substance (i.e. modge podge or paraloid B-72), then embed it into another substance, i.e. epoxy resin. These 2 substances have different refractive indices and does it show in practice or not? I honestly don't know since I haven't tried it myself. BTW, Paraloid/acryloid B-72 is preferred by conservators since it is not known to yellow with age. White glue definitely does. Epoxy resin may also yellow with age.  

I’ve used resins for about 8-9 years, I love making stuff with it. As of yet I haven’t had any issues with the Modge Podge melding with the resin. Once it’s completely encased, and provided one hasn’t oversaturated the embedment, you can’t even tell it’s there. Technically it’s an adhesive, but it’s thin enough and dries clear enough that a lot of folks use it to stabilize flexible or porous items for embedding. For really porous stuff like wood I’ll use a vacuum chamber and Cactus Juice(a brand of stabilizing resin). So far I haven’t had anything yellow from the Modge Podge, but who knows how it’ll look in the long run…10, 15, or 20 years. All resins will yellow over time. Some resin brands will begin to yellow within a year even in the shade, whereas some of them will last a few decades, even in direct sunlight, before they start to yellow. UV light is the arch enemy of resins and epoxies. After briefly reading up on the B72, it sounds a whole lot like a mixture of polyaspartic resin polymers and cyanoacrylate(CA glue…aka: superglue). I go through a ton of StarBond CA glue for my wood projects, both as a small crack and pinhole filler and to adhere wood bases to resin castings so I can turn them on the lathe. I’ll definitely have to get some B72 to experiment with on some raw as well as polished rocks. I’d like to embed a tooth, or even several teeth, in a clear blank and turn a sphere on the lathe, with the tooth/teeth at the center. Sorry for the very long-winded response, but I love fossils and I love making things, I’m just trying to find a way to incorporate them and use one to enhance the other. I just need to find a sealant that won’t compromise the sheen or aesthetics of the tooth.