From Dr. Robert Brill, Research Scientist Emeritus:
Dilute hydrofluoric acid (H
2F2) is used to etch glass. It exerts a vigorous chemical attack on glasses that either eats away the glass from the surface rapidly or produces a diffusing (matte) surface effect.
A mixture of concentrated hydrofluoric acid and sulfuric acid (H2SO4) exerts a somewhat slower attack on glasses and is used for acid polishing.
