Casting bugs

[Grover]

So I'm not really into the models thing and I really don't know much about casting at all. What I want to do is insert insects into clear resin blocks, particularly mantises.

I'm looking for some type of cold-setting resin or something that doesn't heat too much so as not to cook the insects.

Also, any tips on getting the best results? Have you tried this before? What shape would be best?

[mangozac]

Hmmm that's an interesting question. To a large degree the amount of heat generated is proportional to the curing time of the resin, and from what I understand clear resins are generally slower curing so that the bubbles rise out ore easily. I've personally not done any playing with this kind of thing so don't have much to tell. Perhaps blind_pig will have some input?

Otherwise your best bet would be to talk with a resin supplier about your requirements....

Good luck, and please keep us posted on your results!

[Grover]

I've read about some low-viscosity resins and cool-setting resins, but I don't know if there are any that combine both of these or if any of them are clear.

[blind pig]

Hmmmmm......Interesting.

I started out in casting as a teenager helping my father (a Geology Lecturer) imbed mineral specimens in acrylic for student use.

What we used to do was:

1. clean mineral to be imbedded (duh)
2. Get a used, clean milk container (paper type) and fill with clear acrylic resin to about 1"
3. Wait for resin to cure
4. Place specimen into milk container ontop of cured resin
5. Pour resin onto cured resin in milk container (not onto specimen) using the smallest amount
of catalyst possible.
6. Tap milk container to release air bubbles.
7. Wait to cure.
8. Rip milk container away from cured resin
9. with increasing fineness of sandpaper, start sanding the cured resin, finishing all sizes with
1200grit wet and dry.

The problems of this method were:

1. Milk container is an uneven shape inside, requiring LOTS of sanding or cutting surfaces first
with a diamond saw.
2. Acrylic resin can get really hot! and even fracture if too much catalyst is used.
3. Slow.
4. Trapped airbubbles.
5. Acrylic can shatter when dropped from table height!

What would I do to improve this method?

1. Use a clear polyurethane resin. It does get comfortably warm, but not hot enough to cook human
skin.
2. Use the correct surfactant for the clear polyurethane to help remove bubbles (This surfactant can
make a huge difference, even with normal polyurethane resins)
3. Make a mould from silicone
4. Vacuum degas polyurethane prior to pouring
5. fill mould to that 1" level and allow to set under high pressure (60+ PSI)
6. Insert Specimen and cover with degassed (vacuumed) resin.
7. Pressure (60+ PSI) to cure.

The big problems are that you may not have access to vacuum and pressure casting rig, and that the bug you want imbedded may not do oo well under pressure(?)

I have experimented with clear polyurethanes in the past and without using the surfactant, vacuum and pressure, the resin is filled with tens of thousands of airbubbles and would be useless for any sort of display purposes.

[Grover]

Have you ever tried low-viscosity resins? I would assume it would help with bubbles.

How hot exactly does it get? If it gets cooled while it sets, will that affect it negatively? I wouldn't want the heat to burn my bugs or mess them up.

Someone recommended sticking part of the bug in the first section of resin when it has started to thicken and then pouring the rest over it after, section by section.

If you make one section at a time, does it leave any visible seams?

[blind pig]

[Grover]

That's a lot of good information, thanks!

I may have to experiment quickly to find out what works best. I have a nice, brightly colored female mantis that I want to preserve. It's just about 3 inches long and it's nearing the end of its natural life. I'm going to have to test it out on big grasshoppers because they're similar, and I don't want to have to wait for the next generation of mantises to get it right.

Since I don't have any equipment for vacuum or pressure casting, what would you recommend for getting the best results? Would vibration help get rid of bubbles?

[mangozac]

Yeah I think ultimately experimentation using common bugs you don't mind using will be the best bet.

Some people do use vibration in their moulding and casting processes, generally by converting an old sander into a vibration table. I nice low viscosity, long curing time resin and the vibration table should do the trick.

One other idea I just had (but without any idea as to its suitability) is a water effects style resin. This is the stuff they use to make water for things to do with miniatures. From what I understand it's very slow setting and doesn't generate much heat. I'm pretty sure you would have to do it in a few layers though. I've not used it but it might be worth investigating.

[Arkangel]

Amazingly enough and probably to Zac and Warhounds surprise , I do, have some experience in this area. Mainly for a project I've told warhound about and unfortunately one I cant divulge on here until I get the chance to unveil it However I can tell you that I've done some experimentation with plastic miniatures in clear resin, and as Zac and Blind pig have mentioned the only real issue, and one that I had during the process, is removing the bubbles. I'm currently on a course at the moment with work however when I get back at the weekend I'll let you know all the product details.
It's got a long curing time and low heat output, I actually placed the mini in a plastic beaker/cup and then used the clear resin, that way I could just pull the plastic cup off and throw it away without worry about mould issues, especially as it was a test. Making a mould from just some plasticard in cube shape would do the trick too, or the usual lego bricks, small pane of glass and some plasticene
However, the bubbles issue is the one hurdle you're going to need to jump, and with clear resin, that too for me is yet to be mastered.

[blind pig]

Well, Armsmodelit here in Queensland have this:

http://www.armsmodelit.com.au/product.a ... y=EASYCAST CLEAR CASTING EPOXY

And I suspect it is similar to the stuff mangozac mentioned and something I use to make water effects on gaming scenery. IIRC it is called "Envirotex" (sp?)

I have some in the shed, and am wondering if I can be bothered going out into the sub-tropical downpour we are having at the moment to put it in an old mould and give it a go?

I know it takes about 12 hours to set, and I have never poured more than 10mm thickness at any one time......

[blind pig]

Ok, so I have poured 160 grams of the Envirotex into a mould and I'll show you all tomorrow what it looks like.....

Here are some photos of some Easycast Clear (dyed blue with PSTF Brilliant Blue from Barnes) for the Plasma Pistol I did up a few weeks ago.

Straight EasyCast Clear cured in the open air:



EasyCast Clear with about 60PSI pressure:



EasyCast Clear with about 60PSI and the Surfactant (Anti Foam AF4 from Barnes):



As you can see, there is a *huge* difference with the results between the three methods.
No vacuum was used to de-gas the resin prior to pouring.

What would pressure do to bugs, BTW?

[Grover]

This is starting to seem like a much bigger ordeal than I had expected.

All I really wanted was to keep bugs in such a way that they could be displayed without drying out or becoming too fragile.

[mangozac]

Don't despair Grover - we'll see what this Envirotex turns out like when Bec posts the result

[Grover]

Well even if this doesn't work out, you guys have been very helpful and attentive.

[blind pig]