Silastic E RTV Silicone Rubber is one of Dow Corning’s highest viscosity two-part silicone rubbers. It has a viscosity of 100,000 cps with a Shore A hardness of 35 and a tear strength of 100. It has a long working time and is heat-accelerable curing. It has high elongation and virtually no shrinkage. It is especially good for patterns with unusual configurations, severe undercuts and close tolerances. Vacuum deairing is required. There is inhibition sensitivity to some modeling clays and adhesives which could cause incomplete cure of mold.