Polymer clay to make a negative

[coryatjohn]

I needed to get the exact geometry off of a rubber part and used polymer clay to do it.

The Sculpey Premo clay I used has the consistency of warm beeswax and is pretty easy to work. Once fitted to the rubber part, I put a backer piece to keep it from torquing and fired it at 275F for 30 minutes.

The result is a very strong piece that can be sanded, polished and painted.


Here's the rubber piece for the impression. The powder on the surface is sodium bicarbonate which is used as a release agent. The powder is quite fine but the camera makes it look a lot more granular.
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Here's the clay squished into the rubber. The clay is soft enough to conform without distorting the rubber. If it does distort a bit, just let it sit and the tension in the rubber will move the clay into the proper orientation.
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The backer plate stabilizes the geometry and also becomes a base for when it's fired. I used PVA as a release agent on the metal.
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This is right after pulling it from the rubber. Note the detail. The black spots are some grease on the rubber. It won't affect the finished piece.
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Once fired, the material is strong, tough and pretty hard.