I got some of that white plastic molding stuff (not sure the name) from McKenzie. I was just wondering if that stuff is supposed to expand when you put it in the mold. I just got it to try out and made some rubber molds of rocks. The first one I did I put some vaseline in the mold and mix the stuff 50/50 and poured it in and it worked fine. I was going to try adding some powder tempra paint to the mix. So I did the same things but put some brown tempra in before mixxing. Well I mixed it and poured and it expanded like an inch out of the mold. Maybe it was the tempra paint I guess. So should I just make the mold white then paint the rock or whatever it is that im making? Also is vaseline ok to use as a release or should I get that special mold relase stuff. Havent had any trouble with the vaseline yet. Thanks for any help, Kevin
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Not familiar with the actual product, but it sounds like a polyurethane. PU are notorious for bubbling whenever moister is introduced. They make special polyurethane pigments/dyes that work really well. The ones I know of are from Polytek. Very strong color so little is needed. What kind of mold is it? If it's a silicone mold then no release is really needed. You can use vasoline, if you thin it down with mineral spirits about a 80%/20% - 90%/10% mineral spirits to vasaline works fine.
Good luck.
~ Niki