Manufacture of glass wherein hot metal molds are provided with a solid

Abstract

An improvement is provided in methods for forming glass articles which methods are of the type wherein hot formable glass is first formed into a parison, or blank, in a parison or a blank mold and then the parison, or blank, is formed into the final glass article in a blow mold and wherein there is no relative rotation of the glass and the respective molds in the forming operation; the improvement resides in providing the cavity-defining surface of the blank mold with a layer, or coating, of a solid film lubricant or glass release agent which essentially comprises a non-colloidal lubricating graphite dispersed in a thermoset, cured, hard organopolysiloxane binder. The layer, or coating, is formed by applying a dispersion of graphite in an organic solvent solution of a further-curable, thermosettable, solvent soluble, organopolysiloxane onto the cavity defining surface of the blank mold and then curing said organopolysiloxane to a thermoset hard condition. In another embodiment of this invention, the blank mold and the blow mold will both carry such a layer, or coating, but the blow mold will have a layer in which the graphite particle size is no larger than the size of the graphite employed in the blank mold layer and, preferably, will be smaller than the size of the graphite employed in the blank mold layer.