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Casting beetles in a vacuum chamber

DLJeffs

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Thanks Kyle, I'll search those organizations for info. Regarding the casting - I'll carefully remove the pins and then the beetles will be taken off the styrofoam. I only used the stryofoam to pin the bugs into position I wanted them to dry. They're really really fragile when dry (and these have been pinned this way since I was in high school back in the 70's). You have to be very careful with the claws so they don't hang up in the foam. Ditto for the antennae. I'll cast a thin layer in the bottom of a container and when it's about 80% set up I'll stick the beetle in, making sure it adheres to the bottom layer. That keeps the beetle from floating. Usually we poured the rest of the casting in two layers rather than all at once to minimize the heat expansion.

If I used the vac chamber, I guess I'd put the mixed resin in the chamber, vac it until I didn't see any more bubbles, and then take it out of the chamber and pour it over the beetle. That probably helps but it's the air inside the beetle that seems to be the biggest problem.
 
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Sprung

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I've no direct experience with casting, but generally casting is done under pressure, not vacuum, to reduce air bubbles. But you have to have a pressure pot for that.
 

JerseyHighlander

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Thanks Kyle, I'll search those organizations for info. Regarding the casting - I'll carefully remove the pins and then the beetles will be taken off the styrofoam. I only used the stryofoam to pin the bugs into position I wanted them to dry. They're really really fragile when dry (and these have been pinned this way since I was in high school back in the 70's). You have to be very careful with the claws so they don't hang up in the foam. Ditto for the antennae. I'll cast a thin layer in the bottom of a container and when it's about 80% set up I'll stick the beetle in, making sure it adheres to the bottom layer. That keeps the beetle from floating. Usually we poured the rest of the casting in two layers rather than all at once to minimize the heat expansion.

If I used the vac chamber, I guess I'd put the mixed resin in the chamber, vac it until I didn't see any more bubbles, and then take it out of the chamber and pour it over the beetle. That probably helps but it's the air inside the beetle that seems to be the biggest problem.
Any possibility of drill a couple small inconspicuous holes in the bugs and using a syringe of some kind to inject resin inside, forcing out the air?
 

Igor

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Hi Igor,
Thanks for bringing some ideas and suggestions. When you say "greased with resin", do you coat the beetle and then allow it to cure? Or coat the beetle, and then immediately start the casting process while that coating is still wet?

The reason I got the epoxy instead of the polyester resin is because they claimed the epoxy does not get nearly as warm during the curing process. When we did this many years ago while still living in Panama, it was the heat that caused the air inside the beetle to expand and flow out, resulting in a silvery sheen around the beetle. That's the main thing I'm trying to prevent. A few little air bubbles aren't as bad, but that silvery covering around any part of the beetle pretty much ruins it.
The peeling of the beetle in the resin can occur from its drying out and from the shrinkage of the resin, as well as the chemical composition of the carapace itself.
I fill it when the coating is still sticky. but no resin remains on the finger
We use LERPOL CRYSTAL 025 / P resin for transparent castings. Look if you have analogs
 

DLJeffs

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The peeling of the beetle in the resin can occur from its drying out and from the shrinkage of the resin, as well as the chemical composition of the carapace itself.
I fill it when the coating is still sticky. but no resin remains on the finger
We use LERPOL CRYSTAL 025 / P resin for transparent castings. Look if you have analogs
Thanks Igor. I'll research LERPOL resins. It looks like they're made by a company named Laversan
 

DLJeffs

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Any possibility of drill a couple small inconspicuous holes in the bugs and using a syringe of some kind to inject resin inside, forcing out the air?
Kyle, we did try that a few times. Used a needle to poke one or more small holes in the top of the beetle, usually in a joint or some place where the hole wouldn't be seen. We even gently compressed the carapace, trying to squeeze out air and suck in resin. That's a very delicate operation because if the body isn't supported by cured resin, all the pressure forms in the leg joints and you bust off a leg or two.
 
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