The process of decorating cold glass by removal of material can be done in several ways: direct engraving (wheel engraving and etching) or indirect engraving (acid etching and sandblasting). Acid etching consists of plunging the cold glass into a bath of hydrofluoric acid. The decoration is affected by the corrosive action of the acid, while any surfaces protected by a painted on coat of bitumen resist the acid and remain transparent.

This technique, foreseen at the end of the XVIIth century, will not be fully developed until the next century with the discovery of how to make wider use of hydrofluoric acid. This acid begins to be used for industrial purposes in 1855 owing to the chemist L. Kessler who managed to manufacture it safely and economically. Depending on the concentration of the acid bath, in solution with water or other acids, and the duration of immersion, acid etching can produce different textures -- flat, satiny or frosted.

The process of acid etching is rarely practiced anymore in small artisans’ studios