Casting rigid foam in a plaster mold

[Lukea]

Hello, I need to cast expanding foam in a plaster mold. I don't want to use a messy release agent like Vaseline. Is there a paint or something I can brush in that will peel away with the foam when I demold? Thanks in advance.

 

[udog]

Wax would be the release. You can spray an acrylic paint spray (the fast setting kind, used for cars etc.) to seal the plaster.
What kind of piece ar you casting?.

 

[Lukea]

Thanks for the reply. I am casting a shoe with no undercuts. I want to pour a 5 or 6 pound foam into the plaster mold. I really don’t want a waxy or oily mold release that will make painting the casting impossible. I assume a wax or oil release will be all over the part when it comes out of the mold. I will have to clean the part before painting and I don’t even know if that is possible. Can I use a powder as a release?

 

[PFMF]

Thanks for the reply. I am casting a shoe with no undercuts. I want to pour a 5 or 6 pound foam into the plaster mold. I really don’t want a waxy or oily mold release that will make painting the casting impossible. I assume a wax or oil release will be all over the part when it comes out of the mold. I will have to clean the part before painting and I don’t even know if that is possible. Can I use a powder as a release?

There will be some, but cleanup is alwas a must. A release agent in itself is a substance that creats a surface that can easily sepereted. Some residue will always remain. Sealing the surface and using mold realease wax is the best I can recommend too.
Sorry to say, but unless you are doing latex in a plastermold, you will always have realese residue on your parts. (And with latex to to a degree, a the plaster is the moldrealese for the latex and leaves sone residue)
Just clean it up with some soap, water and/or a bit of alcohol after casting.