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There are some platinum cure RTV silicones that can be used for molds that will withstand 1,000 or more castings with little or no loss of detail, when used with the right mold release compounds and compatible resins. From a glossy surface original, RTV silicone can reproduce details as fine as fingerprints, and replicate them in the castings. Soft urethane rubber can be used to make molds at less cost than silicone, but extreme care must be taken with applying mold release when casting urethane resin in urethane rubber molds because the resin will easily and permanently bond to the rubber. There are two main types of RTV silicone used for making molds. Platinum cure, which is the most expensive but has a very long shelf life for cured molds and can be formulated to have essentially zero shrinkage. Platinum cure is also compatible with the widest variety of resins. Tin cure is slightly less expensive but the molds will eventually deteriorate even when not used, and it also inhibits the cure of some types of resins and platinum cure silicone. Tin cure silicone exhibits more shrinkage than platinum cure. Bizzybody (talk) 05:08, 2 June 2014 (UTC)Reply
