Chapter 3 - RTV Molds
RTV (Room Temperature Vulcanizing) silicone rubber must be one of the best mold making materials available to the hobby mold maker. Although it requires a vacuum pump and a vacuum chamber to achieve the best results with some of the RTV Silicones of high viscosity. There are available RTV Silicones that are thin and will de-air without such apparatus.
A Split Mold for Injecting Wax By Ray Brandes