This invention relates to the preparation of a partially quaternized ammonium organosilane composition, and a self-stabilizing aqueous solution of said composition, which serves to yield an antimicrobial polysilsesquioxane coating upon thermal curing. By way of this invention, an aqueous solution is prepared, comprised in part by a partially quaternized ammonium organosilane hydrolysate, characterized in that no further manipulation or addition of potentially costly ingredients are required to yield a stable and hence marketable product.