Low Shrinkage Tin Cure Silicone Rubber 25 Shore A RTV-2 Liquid for Sculpture Molds This low-shrinkage 25 Shore A tin cure (condensation-cure) RTV-2 liquid silicone rubber is a two-component mold-making silicone supplied as HN-625 in the HN-6XX series. Mixed at a simple 100:2 ratio by weight and cured at room temperature, it forms a flexible yet tough elastomer with no oil bleed, exceptional detail reproduction, high tear strength and low linear shrinkage (≤0.2%) — a factory