Silane modification of mineral surfaces has been used primarily to improve adhesion and water resistance in plastics through a coupling mechanism. Wet-out on filler (displacement of air) and dispersion (elimination of clumps) with control of viscosity, settling, and appearance may be of equal importance. A study of commercial surface-active agents (as used in the paint industry) along with appropriate silanes shows that handling properties of filled plastics may be controlled while retaining, or improving the coupling activity of the silane.