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Casting Crystals?

I want to fabricate and cast crystals to then cast in glass. I've done glass casting before, but not much mold making. If I have a wax positive, I can melt it out of the plaster/silica mold so it doesn't have to be a 2-part mold as long as there aren't any undercuts, which there won't be. My question is how can I fabricate and then cast crystals to then cast in wax to make my glass mold? I'd like to work with silicone since it is flexible and then I won't have to make a 2-part mold. I thought about cutting foam to make the crystals, but I want the edges to be very smooth so that the glass casts look like crystals. I also thought about carving glycerine soap and casting that, but not sure how it would hold up to being cast with any flexible mold-making materials like silicone. Any advice?

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shortone (author) 4 years ago
Yes, I'll be using lost wax casting methods for the glass with wax and a silica/plaster mold. I think I will use silicone for the first mold to mold the wax, but I'm not sure what to make the crystal positives out of. I was thinking soap since it is easy to carve and has a smooth surface, but it wouldn't hold up to the silicone casting method. :/
Why not use cheap glass crystals ?
Burf4 years ago
Use sealing wax, it will cast with sharp, clean edges, smooth surfaces, has a melting point well within the tolerances of the silicone and is hard enough to make your ceramic mold on.
rickharris4 years ago
I think foam will break up when you try to de mould it - this may be an advantage

MDF and common power tools?

How big do you want them to be.
frollard4 years ago
Silicone would be ideal - it can hold a mirror finish, so long as your source 'crystal' is smooth. It can do some neat things like you say with stretching over the original 'glove' moulding rather than having multiple parts.

I'm saying this assuming you mean to make the lost wax portion. No silicone I know of would survive the >1000 degree molten glass.