Saturday, October 2, 2010

Silicone Rubber for Molds

What is a silicone mold?

Silicone molds may not be the best thing since sliced bread, but they come close—at least for resin crafting and gaming enthusiasts and artists! Silicone molds are resistant to high temperature and chemicals, can accurately capture fine detail, and they’re elastic and durable.

Silicone is a mold-making elastomer—usually made of two liquid parts, a base and a curing agent (often called catalyst), which are easily cast around an original artifact after being mixed. Once hardened, elastomers become a flexible, stretchable (which eases demolding even around deep undercuts), yet return to their original shape without distortion.

When were the first silicone molds available?

The first recorded reference to a silicone mold appeared in the 1950’s; however, the earliest referenced silicone molds where the details of an original surface was actually transferred using a mold appear to have been dental molds, referenced in a 1952 document. Commercial products for these dental molds were available from 1955 on, with fast-curing compositions appearing later.

I’ve heard that making a silicone mold is hard—requiring a gram weight scale and a degassing vacuum. Is there someplace I can have a custom silicone mold made?

Yes—contact Cindy, the ResinLady, at, but before you do, you should look at some of the newer formulations of silicone rubber. They are easier to use than ever before. Now you can make your own finely detailed molds with all the advantages silicone offers, PLUS no more weighing or degassing the liquid after mixing! Check the manufacturer’s instructions to be sure that the rubber has the characteristics you are looking for.

I’ve tried making my own silicone mold and had a disaster—it was filled with air bubbles, even though it was not supposed to need degassing! Is there any way to avoid that?

First, never pour the silicone mixture directly on the original; pour it into a corner, letting the liquid flow around the artifact. There are also formulations that are thinner and less prone to bubbling, or you can add a thinning agent. Read the manufacturer’s instructions to find a product like this, or contact Cindy at ResinObsession to answer your questions. offers ready-made silicone molds for sale, and time-permitting, makes custom molds, too. Cindy also carries a complete line of silicone mold rubber and putty for all of your mold-making projects.

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