Abstract: The method of modifying an organic material including rubber and plastics which consists in the steps of embodying in the organic material during manufacture of the glycerato-zinc complex (C.sub.3 H.sub.6 O.sub.3 Zn) which is manufactured by heating a zinc compound and glycerol to a temperature below the boiling point of the glycerol to form crystals having substantial two-dimensional extension but low thickness and orientating the crystals selectively to improve tensile strength and reduce ultraviolet light degradation of the organic material.