Casting beetles in a vacuum chamber

[DLJeffs]

Barry's picture of that big beetle reminded me of this.

This is not a wood working question but I know there are quite a few folks on here who cast various things in resin. When my family lived in the Canal Zone, one thing we got into was going out at night searching for any of the large beetles that would be attracted to the lights. I'd inject them with formaldehyde and then pin them onto a styrofoam board and let them dry. Then we'd pour them in clear two-part epoxy. Dad would square them up on the band saw and we'd sand and polish them in the wood shop at the high school. But we often had a problem. The epoxy was exothermic so generated heat as it cured. That heat caused the air inside the beetles to expand. Since the epoxy was curing, the air had no where to escape and would flow around the beetle resulting in a silver lining, which more or less ruined the whole thing. I always thought pouring them in a vacuum was the solution but we didn't have a vacuum chamber. I still have a few beetles that I'd like to preserve in clear resin and now I have a vacuum chamber. My Canal Zone experience was over 40 years ago so I'm hoping there have been advancements in resins and techniques. So I'm posting this thread asking for any advice or related links from people who have cast resin in a vacuum chamber. Looking for advice about the type of resin, the source, techniques for pouring, especially about trying to minimize the air bubble and entrapped air problem. Thanks. Feel free to send me a message and we can take this off line so we don't tie up forum space too.

 

[Nature Man]

I swear I'm seeing aliens! Chuck

 

[DLJeffs]

Naw, just bugs. These are all fairly common beetles. The top one we called a coconut beetle because they often bored holes into coconuts. The mandibles on that beetle are formidable - we like to stick a pencil in there and watch the beetle cut it in half. Needless to say we were very careful handling those buggers. That one's about 6 inches long not counting the antennae. It's obviously in the family of longhorn beetles.

The middle pair consists of a female rhinoceros beetle and a fire beetle. The fire beetles are cool because like a hummingbird, their colors change depending on how the light hits them.

The bottom one is a male rhinoceros beetle. That one is about the size of a tennis ball. not including the legs. They use the horn to pries open rotten logs on which they feed. The larva will bore into the rotten wood and live in there until they reach maturity. We discovered that the best time to hunt them was right after the first rains after the dry season ended. The rain must be a trigger for them to emerge.

 

[FranklinWorkshops]

Doug, those are so neat. Brings back great memories of a grammar school project all us kids had to do. I grew up on a farm so had a little advantage on finding and mounting all kinds of bugs. I remember my teacher being shocked at how many I found for the project. I'll bet there are many thousands of species in Panama since the climate would be perfect for them.

 

[Wildthings]

I would think dipping them in resin first and hanging to dry. Maybe a couple times. This would seal the beetle for the final pour or two. For the final pour maybe two pours. First one halfway and second one to finish. There's new resin that doesn't heat up like those did back then

 

[Maverick]

 

[Wildthings]

OH BTW final pictures are required!!

 

[DLJeffs]

I have to go down to the Bay area in a week or so and I'll stop by TAP Plastics and talk to them about their casting resin and process. Might be able to save on postage if I can buy some in person.

 

[DLJeffs]

Well, TAP Plastics wasn't open so I wasn't able to talk with them. From researching resin web sites it seems like pre-coating the bugs is the preferred method. EntomologyToday reported on testing they did on various methods and concluded that pre-coating worked best and then making the final pour with the beetle upside down (better access to the ventral side helped prevent formation of air bubbles when adding resin and gives access to tickle any bubbles away. I did find one site that tried using a vac system and the resin just has too much entrained air and foaming was a problem. Please let me know if you stumble on any related advice.

 

[Wildthings]

I would think dipping them in resin first and hanging to dry. Maybe a couple times. This would seal the beetle for the final pour or two. For the final pour maybe two pours. First one halfway and second one to finish. There's new resin that doesn't heat up like those did back then

Well, TAP Plastics wasn't open so I wasn't able to talk with them. From researching resin web sites it seems like pre-coating the bugs is the preferred method. EntomologyToday reported on testing they did on various methods and concluded that pre-coating worked best and then making the final pour with the beetle upside down (better access to the ventral side helped prevent formation of air bubbles when adding resin and gives access to tickle any bubbles away. I did find one site that tried using a vac system and the resin just has too much entrained air and foaming was a problem. Please let me know if you stumble on any related advice.

 

[ripjack13]

Feel free to send me a message and we can take this off line so we don't tie up forum space too.

That's not a problem. I'd rather keep it here just in case anyone else doing research may be able to read up on it here.

 

[Ken Martin]

I know absolutely nothing about casting - in fact, I came here to learn about it. BUT, it seems to me that if a vacuum chamber caused foaming, then a pressure chamber might be your solution.

That’s the extent of my knowledge on this subject - no facts, just theory. Good luck!! I’d love to see finished result pics, though.

 

[DLJeffs]

Drove down to Benicia last week for grandson's 2d birthday and daughter's birthday. Lots of cake and ice cream. Took an hour to drive over to Tap Plastic's and pick up some casting resin to try to cast these beetles (finally). This stuff is expensive. Supposedly, this epoxy doesn't heat up as much as the old stuff so hopefully I'll avoid the air expansion problem. Stay tuned, I'll post pics.

 

[2feathers Creative Making]

Also, might try warming the beetle a bit just before casting in seal coat, then warming again just before casting full depth. That should keep the heat of the resin from pushing air out as your beetle heats up as it would do if cold cast

 

[Tony]

 

[Igor]

My son is passionate about this, and he says that the beetle needs to be dried well and first greased with resin.

 

[Bigg081]

So cool!

 

[Igor]

Drove down to Benicia last week for grandson's 2d birthday and daughter's birthday. Lots of cake and ice cream. Took an hour to drive over to Tap Plastic's and pick up some casting resin to try to cast these beetles (finally). This stuff is expensive. Supposedly, this epoxy doesn't heat up as much as the old stuff so hopefully I'll avoid the air expansion problem. Stay tuned, I'll post pics.

View attachment 216132

And why epoxy resins, there are polyester resins for such castings. They are much cheaper, the result is the same.

 

[DLJeffs]

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.

 

[JerseyHighlander]

I couldn't get a read on whether you were going to keep it on the styrofoam or not?
Spent a bit of time building museum exhibits and environmental education centers etc. so have been around this a lot but wasn't my world. I remember using the vacuum to pull all the entrained air out of the resin first and then pouring it, but not using the vacuum after it was poured. Certain things would crush or explode, like that foam.

You may be able to get some information on the web site of or by contacting the; Smithsonian, Museum of Natural History or the National Park Service. The Park Service in particular I remember has a lot of information available to the public. Tons of it pertaining to historic preservation of houses, not sure about exhibit making etc. but I know they employ a lot of people who do exactly that and they love to share.