Making Silicone Rubber Mold

October 13, 2011 MaryMay Coat of Arms

This was a nerve-wracking day. After spending many hours carving a coat of arms, I have just completely enclosed it in goo. Sticky, gooey, icky stuff.

I brushed shellac over the surface of my carving to seal the wood (this will be painted in the end, so the finish color is not critical). The reason I needed to seal the wood is that I will be brushing a release agent (vasaline disolved in naptha) on the carving so the silicone rubber will release easily. There are all sorts of spray release agents, but I really needed to be able to brush into all the tiny areas that the spray may not have been able to reach. By brushing shellac on the surface of the wood, this will prevent the release agent from soaking into the wood and causing potential issues with the painting process. It will be easy to remove the vasaline/naptha with a solvent, and simply leave the shellac finish.

Next I made this very professional mold enclosure (cardboard box with duct tape).

Then I hot-melt glued the bottom of my carving to the cardboard. I made the mistake of not doing this one time, and the wood floated to the top of the rubber goo - completely messed up my rubber mold.

Then my friend, Nancy Newton (who is a brilliant gold leaf artist), helped me mix about 2 gallons of silicone rubber. It felt like we were in high school doing one of those science experiments where it is so critical to get the correct weight. The mixture needed to be mixed 10 to 1 by weight. There was one time, several years ago, when I mixed it wrong and it never actually set. When that happens, you might as well just write off the carving because there is no way of getting the goo off – it is like really sticky taffy.

So, now I wait – it should be fully set after about 7 or 8 hours. So far, everything looks to be setting nicely – no issues.

Tomorrow is like Christmas!

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