Foam Casting

[Troy]

Hey everyone, i'm new to the community.
I'm wanting to sculpt faces in clay, cast them and then make a styrofoam copy.
Question
1. Has anyone done this?
2. Could I make a hydro cal mold?
3. If yes, what type or release agent should I use?
4. Any suggestions on what foam to use?

Thanks for any direction you can give.
Troy

[Arrow]

You can cast polyurethane foam in rubber and plaster molds....

But if your thinking about expanding polystyrene beads (the stuff cups and beanbags are filled with). You would need a metal mold, usually aluminum. And a steam system or large boiling pot depending on mold size. They fuse from expansion pressure from the gas trapped inside each bead.

http://www.iasco-tesco.com/
This company has both pour foam and expanding beads for aluminum molds....limited site more stuff their printed catalog.

[GaryR52]

Depending upon what you're going to do with the foam (are you going to cover it with fiberglass, or use it as a pattern, to be burned out for bronze casting?) and whether you have an original with an intricate shape, you could use either Hydrocal or an RTV rubber mold material. I'd recommend the RTV rubber mold material if you need a mold that is flexible and easily removed.

If your end goal is to cover the foam with fiberglass, you'll want to use polyurethane foam, as EPS (expanded polystyrene) melts when exposed to polysester resin. In fact, you'll probably have to use polyurethane, as you'll need a pourable foam kit (http://www.fiberglasssupply.com/Product_Catalog/Pour_Foam/pour_foam.html) and I don't believe pourable polystrene kits exist.

Gary

[bluedogshuz]

Gary, Aren't you confused? I mean if a casting is being made of a face, seems like you could lay up epoxy in a silicone or rubber mold and then add urethane, right? If using eps why cant you cover it with polystryene? Im confused! I use eps and cover it with epoxy resin, whats the dif?

[sculptor]

hi Troy

I tried casting a 2 part foam into a hydrocal piece mold several years ago and had sealed the mold with 3 layers of lacquer, then shellac and wax and the foam ate through it all and found all the tiny holes in the hydrocal and mated with it for life-----chiseling away the hydrocal didn't work as the foam was less hard and tore away------I was left with only a torso (kiss off several months of working with a model and the clay)

I wish you better luck---------
perhaps you'll need a rubber mold within the mother
rod

[Troy]

Thanks for all the help.
Troy

[GaryR52]

Gary, Aren't you confused? I mean if a casting is being made of a face, seems like you could lay up epoxy in a silicone or rubber mold and then add urethane, right? If using eps why cant you cover it with polystryene? Im confused! I use eps and cover it with epoxy resin, whats the dif?

Ummm...well, I wasn't confused, Blue, but now I am. You do realize that EPS stands for Expanded Polystyrene, right? In other words, EPS is polystyrene. And, yes, you can cover EPS with epoxy resin, but not with polyester resin, which must have been what you meant to say instead of "...cover it with polystyrene," right? If so, then the answer, as I said above, is that you can't cover EPS with polyester resin without melting the foam, unless you first cover the EPS with a barrier coat of something that will protect it. Epoxy resin is safe to use directly on EPS.

Gary