Summary: Silicones have been incorporated in personal care products since the 1950s. Initially used in skin care products, and more recently in hair care applications, silicones are recognized for their lubricating properties and for the characteristic soft smooth feel they impart. With recent advances in silicone technology, these fluids can also provide substantivity and durability.Resinous silicones such as trimethylsiloxysilicate act as effective substantivity additives when combined with dimethyl silicone in skin care formulations. In tests evaluating the number of wash cycles required to penetrate a silicone barrier, resistance to removal increases markedly as the proportion of resinous silicone to dimethyl silicone is increased. This improvement is related directly to decreased solubility of the resin.