Method for forming flat glass-ceramic articles

Abstract

This invention contemplates a near net-shape method of making thin glass-ceramic articles possessing substantially uniform thickness and parallel opposing surfaces comprising the steps of: (a) heating the receiving and opposing molding surfaces of a mold to predetermined different temperatures; (b) bringing the receiving and opposing molding surfaces of the mold into close proximity to each other to press a delivered charge of molten glass to fill said mold, while thermally providing and maintaining a substantially parallel fit between the receiving and opposing surfaces of the mold, to achieve substantially uniform thickness in the pressed charge, (c) pressing the glass charge for a time sufficient to remove enough heat from the glass charge that the temperatures of the molding surfaces and the glass article surfaces are all nearly at equilibrium, wherein the press time and mold temperature differential combine to result in symmetric heat removal thereby causing all the aforementioned temperatures to reach equilibrium at nearly the same time, (d) removing the glass article from the mold; (e) covering the opposing surfaces of the glass article with a refractory insulating material; (f) heat treating the covered glass article at a temperature and for a time sufficient to cause the glass article to crystallize in situ to a glass-ceramic article; and (g) cooling the covered glass-ceramic article to room temperature and removing the covering therefrom.