The coating compositions of this invention are prepared by hydrolyzing an alkyltrialkoxysilane or aryltrialkoxysilane of the formula RSi(OR)3, wherein R is alkyl of from 1 to 3 carbons or aryl, such as phenyl, in an aqueous dispersion of colloidal silica, aging them, e.g., for at least about 5 days at a temperature of at least about 18??? C. and then admixing a ??-hydroxyketone compound with the r