Method for making perforations or depressions in a glass work piece

The method of simultaneously opening a large number of very small diameter holes in a glass plate which comprises:

• (1) providing a two piece housing for said glass plate said housing when assembled having a cavity conforming in size and shape to said plate, the lower housing piece having a continuous upper surface and the upper housing piece having a smooth surface and dozens to hundreds of openings in said housing piece conforming in size and position to the holes desired to be made in said plate,
• (2) placing said plate on the upper surface of the lower housing piece and covering the upper surface of the plate with the upper housing piece so that the upper surface of the plate and the lower surface of the upper housing piece are in contact with each other,
• (3) inserting in the openings in said upper housing piece graphite pins snugly fitting said openings and extending above the upper surface of said housing piece,
• (4) disposing on the upper surface of said pins a weight sufficient to cause said pins to exert a pressure of at least 0.2 pound per square inch on said plate,
• (5) heating the entire assembly resulting from steps (1) to (4) in a furnace to a temperature intermediate the softening point and the working point of the glass plate and maintaining such temperature until the pins' descent into the plate ceases and the glass displaced by the descent of the pins flows into the body of the plate causing a slight thickening of the plate,
• (6) cooling said assembly to ambient temperature,
• (7) removing the plate from the housing and removing the pins from the plate,
• (8) annealing the plate and then lapping and polishing it.