These materials are what we call platinum (or addition) cure silicones. In general, they have the highest heat resistance of the silicones and can also handle all of the various types of thermoset plastics. The downside is that they can also be easily inhibited by certain substrates such as sulfur-containing clays or polyurethane and epoxy resins. When using these materials as model surfaces for mold making with these silicones, it may be necessary to seal the surface first with shellac before pouring your mold. (See data sheet.) Mix ratio for this group of materials is 10 to one by weight.
SR-2238 is probably the most versatile silicone we offer because it can be used for casting practically any of the commonly used casting resins, cements, waxes and low melting point metal alloys. This material can also be thickened by the addition of Viscosil II to create brushable compounds fo