The process of etching the surface of glass with hydrofluoric acid. Acid-etched decoration is produced by covering the glass with an acid-resistant substance such as wax, through which the design is scratched. The object is then immersed in hydrofluoric acid, or a mixture of dilute hydrofluoric acid and potassium fluoride is applied to etch the exposed areas of glass. Acid etching was first developed on a commercial scale by Richardson’s of Stourbridge, England, which registered a patent in 1857. An effect superficially similar to weathering can be obtained by exposing glass to fumes of hydrofluoric acid to make an allover matte surface.