Abstract: A method of chemical machining of glass and all single-crystal, polycrystalline and amorphous forms of silica and like materials susceptible to etching by acid fluoride etchants. Relatively high-rate precision machining of deep cuts is enabled by using etching masks which are both highly adherent to glass and silica surfaces and highly resistant to attack by concentrated hydrofluoric acid. The etching mask is preferably a deposited composite of a relatively thin layer of metal highly adherent to said surfaces covered by a relatively thicker layer of etch resistant metal. Preferably, the etching mask surface is then sealed with a wax or an additional electrodeposited sealing layer of etch resistant metal.