Silicone rubbers are two-component systems (base plus curative; A+B) available in a hardness range of very soft to medium. Silicones can be cured with either a platinum catalyst (addition cure) or a tin catalyst (condensation cure). They are available for making molds that are poured, brushed or sprayed on to a model and have performance characteristics that no other mold rubber has.
The combination of good release properties, chemical resistance and heat resistance makes silicone the best choice for production casting of resins.
Also called condensation-cure silicone, these are high-tear silicone rubbers that are known as the “work horse” of the industry because of their performance and economy. Tin cured silicone molds are used for casting wax, gypsum, polymer modified gypsum, etc. but are best known for standing up to production casting of urethane, epoxy and polyester resins. They are also good for casting low temperature melt metal alloys.
Also known as addition-cure silicone, platinums exhibit the lowest long-term shrinkage and have the longest library life of all mold rubbers (with a price tag to match). While good for making molds for casting a variety of materials, platinums also have application and physical properties that other rubbers do not. As a result, they are used for other applications. For example, some are certified “skin safe” and can be applied directly to human skin. They are also used for making prosthetic and orthotic devices, skin safe appliances and effects, etc. Some are certified “food safe” for culinary applications.