"Foam Master- How to mold?" Topic

I am making a master of a building out of blue insulation foam. I plan to make a mold out of silicone. Can I pour the silicone directly over the foam or should I seal it with something first? (and if so what?). I've used the foam before as filler when pouring other silicone molds and the silicone doesn't stick to it but I'm not sure if it would pick up the details.

I don't think you'd need to seal it but make sure there are no recessed areas or holes that the silicone will flow into. It's a good idea to brush the silicone over the original first to make sure there are no air pockets then you can pour over that. A guy I knew that made professional molds surrounded the mold with a box to suck out air bubbles from the silicone but i think you could do without that.

Foam will work just fine for a master. I would not expect it to survive removing it from the new mold through. Pulling the master out of the new mold can be a rough process.