GB803850A - A method for etching glass - Google Patents

Abstract

803,850. Ornamenting glass. FIFE, J. G. (Coming Glass Works). May 20, 1957. No. 15959/57. Class 93 [Also in Group XVI] In a method for selectively etching a glass body with an etching fluid, a coating, which reacts with the etching fluid to exert a neutralizing effect and form a barrier to etching, is applied over that portion of the glass surface which is to remain unetched, whereafter an etching fluid is applied to the portion of the glass to be etched. The etching fluid may be dilute hydrofluoric acid, and the coating contains a watersoluble boron containing material such as boric acid, borax or other alkali-metal borates; and may also contain phosphates, and calcium chloride. Examples, (1) 10 parts H 3 BO 3 , 50 parts water; (2) 10 parts Na 2 B 4 O 7 .1OH 2 O, 50 parts water; (3) 10 parts H 3 BO 3 , 10 parts Na 2 B 4 O 7 .1OH 2 O, 50 parts water; (4) 16 parts H 3 BO 3 , 10 parts Na 2 B 4 O 7 .10H 2 O, 50 parts water; (5) 14.5 parts H 3 BO 3 , 19 parts Na 4 P 2 O 7 , 50 parts water. For perforating a glass sheet 10, Figs. 2 and 4, an opacified crystalline pattern 12 is formed in the glass by exposing it to short-wave (e.g. ultra-violet) radiations through a negative or other suitable pattern-bearing screen, and subjecting it to heat treatment. One surface is then preetched for a few minutes in a spray, stream or bath of 10 per cent hydrofluoric acid solution. forming cavities to a depth of about 10 mm. The coating is then applied to the pre-etched surface by dipping or flowing, providing a smooth continuous film 16 which also fills the cavities. The coated glass is dried at about 140 ‹C. The glass is then immersed in an etching bath. which produces cavities 20. bevelled due to lateral etching. The coating is covered before etching with a wax layer 24. After etching, the wax is removed, and the coating dissolved in warm water. The effective diameter of the resulting perforations is that of the original cavities. A glass article may be covered with resist and wax coatings and a design scribed or cut therein. On etching, cavities are formed extending laterally owing to undercutting action. Specification 699,897 is referred to.