# 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.

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## Nature Man

I swear I'm seeing aliens! Chuck

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## 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.

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## 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.


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## 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

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## Maverick




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## Wildthings

OH BTW final pictures are required!!


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## 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.


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## 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.

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## Wildthings

Wildthings said:


> 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





DLJeffs said:


> 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.

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## ripjack13

DLJeffs said:


> 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.

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## 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.


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## 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.

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## 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

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## Tony




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## Igor

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

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## Bigg081

So cool!


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## Igor

DLJeffs said:


> 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.


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## 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.


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## 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.

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## DLJeffs

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

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.

Reactions: Agree 1


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## JerseyHighlander

DLJeffs said:


> 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?


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## Igor

DLJeffs said:


> 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


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## DLJeffs

Igor said:


> 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


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## DLJeffs

JerseyHighlander said:


> 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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## FloWolF

I know I'm a little late to the party, but I've had several years experience experimenting with resins and stabilisers, with both vacuum and pressure.

The problem with using just pressure is it can crush something as delicate as a carapace, so I would, if I were able, do it in 2 stages:

I'd have my vac chamber set up with another plastic tube running into it, and folded over on the outside and pegged to keep it closed.

I'd put the bug secured into the mold into the tank, then pull full vacuum for 15 minutes or so.

Having already prewarmed, mixed and then degassed the epoxy in a suitable plastic cup in the vac chamber beforehand, I'd then put the open end of the tube into the cup, and undo the bend/clinch in the tube slowly until the resin started to fill the mold, and gradually cover the creature. When it's totally covered, release the pressure, and if needs be transfer to the pressure pot whilst it cures to squish any remaining bubbles and encourage surface penetration into the item within.

This is how I do complicated and/or delicate encapsulations where I want no bubbles inside whatever.

Cheers folks!

Shaun/FloWolF

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## 2feathers Creative Making

That is a delicate process. But sounds about right for delicate items. Glad you piped up before I "tried and erred" on my own. I haven't started but have all the stabilizing supplies including vacuum chamber.

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## FloWolF

2feathers Creative Making said:


> That is a delicate process. But sounds about right for delicate items. Glad you piped up before I "tried and erred" on my own. I haven't started but have all the stabilizing supplies including vacuum chamber.


The process just means the air is out of the voids, and the resin slowly rising fills them up, with the remainder being 'sucked in' when the vacuum is fully released. Minimum stress or disturbance to the object.

One more thing be wary of urethanes for this kind of thing - they are more sensitive to moisture and will tend to off-gas making micro-bubbles where they contact the object, if the object is not full, crispy dry. Some things like your insect you perhaps just do not want to subject to that level of further drying as it will likely make the thing even more brittle.

I use 2:1 clear casting epoxies with the lowest viscosity I can find. Cheers again!

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## DLJeffs

Thanks for chiming in Shaun. I haven't made these castings yet so any and all advice is appreciated. It's funny you described your process - years ago when we started doing this, my science teacher had a bell jar vacuum. I kept trying to figure out how to get a tube into the bell jar and then do exactly what you described - pull a vacuum with the big in there and then fill the mold while in the vacuum and then release the vacuum. But the bell lar was glass and I couldn't figure out how to get a tube in there.

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## Wildthings

FloWolF said:


> I know I'm a little late to the party, but I've had several years experience experimenting with resins and stabilisers, with both vacuum and pressure.
> 
> The problem with using just pressure is it can crush something as delicate as a carapace, so I would, if I were able, do it in 2 stages:
> 
> I'd have my vac chamber set up with another plastic tube running into it, and folded over on the outside and pegged to keep it closed.
> 
> I'd put the bug secured into the mold into the tank, then pull full vacuum for 15 minutes or so.
> 
> Having already prewarmed, mixed and then degassed the epoxy in a suitable plastic cup in the vac chamber beforehand, I'd then put the open end of the tube into the cup, and undo the bend/clinch in the tube slowly until the resin started to fill the mold, and gradually cover the creature. When it's totally covered, release the pressure, and if needs be transfer to the pressure pot whilst it cures to squish any remaining bubbles and encourage surface penetration into the item within.
> 
> This is how I do complicated and/or delicate encapsulations where I want no bubbles inside whatever.
> 
> Cheers folks!
> 
> Shaun/FloWolF


A video of this would be exceptional

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## FloWolF

DLJeffs said:


> Thanks for chiming in Shaun. I haven't made these castings yet so any and all advice is appreciated. It's funny you described your process - years ago when we started doing this, my science teacher had a bell jar vacuum. I kept trying to figure out how to get a tube into the bell jar and then do exactly what you described - pull a vacuum with the big in there and then fill the mold while in the vacuum and then release the vacuum. But the bell lar was glass and I couldn't figure out how to get a tube in there.


My old vac chambers - a mason jar with a new lid cut out of plastic, and an over slow cooker with a bung port where the handle went, and a seal made from silicone caulking - for them I had a large fermenting jug bung with 2 holes in it, one for the vacuum and one for the liquid in, or vacuum release.

The new purpose made one came with a brass fitting for vac and release, with the gauge sat on top, so I drilled another hole, tapered it and I have a small solid bung for it, and also one with a hole drilled through and a plastic tube fitted through it for feeding resin/stabiliser in post-vacuum.

I'll try and get some photos from my phone and onto the PC and then attach to a post or something, but lots my head went to 'merd' years ago, and this last 2 years have finished even more of it off, so I'm not quick or slick at these things!

Cheers again,

Shaun/FloWolF


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## FloWolF

Wildthings said:


> A video of this would be exceptional


I'll do my best! To be honest I don't do that particular process often as I can't afford to keep buying all the resin, but I can do a dummy run video, then try and figure out how to get it from my phone to here - My phone and the Lynux Mint PC don't always get on and I am not handy enough with these things to fix that. 

Cheers!

Shaun/FloWolF


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## 2feathers Creative Making

FloWolF said:


> I'll do my best! To be honest I don't do that particular process often as I can't afford to keep buying all the resin, but I can do a dummy run video, then try and figure out how to get it from my phone to here - My phone and the Lynux Mint PC don't always get on and I am not handy enough with these things to fix that.
> 
> Cheers!
> 
> Shaun/FloWolF


Videos have to go to YouTube before they can be viewed here on woodbarter.

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## FloWolF

Well I just had another stab at it - can't get the PC to open my phone at all. I'll have to find another way!

Can I access these forums from the phone, and upload directly?..


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## FloWolF

2feathers Creative Making said:


> Videos have to go to YouTube before they can be viewed here on woodbarter.


Ahhh... well that's something I've never done. At this rate I'll be lucky to get some stills up lol.


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## FloWolF

Few snapshots from this morning.

Notice the folded purple rag et-al on the vac pump? I broke the exhaust mist filter housing off my spanking new pump a few days ago, and that stuff is the stand-in .

Cheers folks.


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