Smooth-On Smooth-Sil Platinum Silicones cure at room temperature with negligible shrinkage. With different hardnesses to choose from, Smooth-Sil products offer tremendous versatility and are suitable for making production molds of any configuration, large or small. These silicones exhibit good chemical, abrasion and heat resistance. Materials such as plasters, concrete, wax, low-melt metal alloys or resins (urethane, epoxy or polyester) can then be cast into these silicone rubbers without a release agent.