Is it ok to use plastic and rubber casting resins in Plaster molds?

[airair]

i was wondering if it is ok to use plastic and rubber casting resins in Plaster molds?

silicone rtv is quite expensive, so i was thinking of using some plaster of paris and doing 2 part molds that way and then casting with them.

 

[tk1608]

I've heard you can use plaster to make moulds, I've never done it myself though. Seem to recall reading that it's a good idea to paint the inside of the mould. Not sure if that's to seal it to make it less porous, or just to get a smoother finish on the cast....
If the cast will pull straight out, and you have no undercuts I think it would work ok.
Anyway, I'm sure there'll more knowledgable folks here that will help you more.

Cheers

Phil