For making fast sprayed rubber molds that have the best release properties for production casting of resins, plaster, etc. it is a tin silicone rubber that self-thickens for making concrete Spray able -on molds . Properly applied, Mixed 100A:10B by weight, rubber quickly develops thixotropy when mixed in air. Cured with negligible shrinkage to a durable mold rubber good for production casting resins, foams, concrete, plaster and other materials. Application of a support shell is achieved by spraying over the rubber mold after it has fully cured.