Crystallization of Silica on Polished Glass Surfaces

Polished surfaces of different optical glasses leached with diluted nitric acid exhibited (1) fine lines showing against the uniform background of a thin colored film, (2) macroscopic cracking with or without the production of flakes, (3) holes or grooves of Werent forms and sizes, and (4) numerous crystals of different forms of silica on the inside of lines and grooves and spread over the glass surface. The interpretation of such observations may help in the understanding of the nature of polished glass surfaces.