When making silicone rubber molds cleanliness is very important. Mold frames, Vulcanizing plates and all tools used to make different type of natural rubber molds must be cleaned thoroughly.
All parts must be cleaned with lacquer thinner or lighter
fluid. Natural rubber leaves chemical residues which can easily contaminate your silicone rubber mold. You might want to keep a separate set of tools for making
silicone rubber molds. Your model should be cleaned with lighter fluid and steamed.
Silicone rubber is available in different levels of hardness and colors. (Check with your jewelry supplier for the right material to fit your needs). Silicone rubber has the consistency of modeling clay. There is no need to cut and fill small pieces into the model.
Using a clean mold frame cut 2 pieces of silicone and put in bottom of frame. Put model into frame. Tear off some silicone compound with your fingers and squeeze like putty around and into model. The material is soft and pliable. Top off the mold frame with rubber 1/16" higher than mold frame. Put into a preheated vulcanize
330ºF - 350ºF for 15 minutes per 1/4 inch.
Once vulcanized the mold will produce smooth surfaces on all wax patterns without using powder or spray improving the finish of your casting.
Remember to pull mold gently when cutting silicone molds because it cuts like butter.
You do not have to pull as hard as natural rubber. Follow the same cutting procedure as natural rubber molds. Silicone rubber molds cannot be burned to correct detail or correct sprues.