Dowsil 786 white RTV silicone sealant is perfect for nonporous surfaces, showers, tubs, sinks and plumbing fixtures. Dow 786 Silicone Sealant is a one-component, silicone rubber sealant that is suitable for sealing porcelain, cultured marble, glass, painted areas, and other nonporous surfaces and plumbing fixtures for both new and remedial construction. Dow 786 silicone caulk is ideal for usage where high humidity and temperature extremes are present.