Creating a mold out of a model object like a wood carving can be done using a fairly simple process, resulting in a negative template from which many copies of the carving can be made. Since wood is able to absorb some substances, however, you cannot use the most common molding material, plaster. Silicone RTV rubber, on the other hand, is an extremely versatile material that can be used to create molds out of many difficult model materials, including wood. To make a mold of your wood carving out of silicone rubber, complete the following instructions.
Coat your wood carving completely in a mold release agent and let it dry, so that the mold material does not get stuck in the wood grain. While the mold release is drying, build a box frame out of Legos that gives your wood carving a clearance of 1/4 inch on all sides as well as the top and bottom. On the bottom side of the box, roll out a piece of modeling clay for the base.
Mix together a half-batch of silicone RTV rubber in a bowl, stirring together the silicone with the catalyst until you have a smooth, pale version of the catalyst color. Pour the mixture into the Legos molding box, stopping when you reach the halfway point, then press the wood carving into the rubber mixture. Around the wood carving, press small wooden craft balls into the rubber to create keying depressions. Let the rubber cure overnight, leaving the wood carving inside.
Remove the wooden balls from the molding box. Mix together the rest of the silicone RTV rubber and pour it on top of the cured rubber, covering the wood carving completely. Let the rubber cure overnight.
Take apart the molding box and peel away the modeling clay, then separate the rubber mold halves. Remove the wooden carving carefully.
Carve a channel in the top of each mold half with the razor, so that there is a connection between the top of the mold and the hollow inside. Strap the mold back together again with rubber bands. You can now pour your casting material into the hole in the top of the mold, and separate the mold halves when the casting material has cured.
Wear latex gloves when handling the silicone rubber, and work in a room with forced ventilation.