The Influence of Founding Time and Temperature on the Fluorine Content of an Opal Glass

JSGT 1952 V36 T270-T274

A study of the influence of founding time and temperature on the fluorine content of an opal glass showed that there is an equilibrium concentration of fluorine in the melt and that fluorine in excess of this quantity is rapidly removed under founding conditions. The presence of fluorine, whether precipitated as fluorides or not, reduces the density and refractive index of the system. The appearance of opalescence in a fluoride-containing glass is markedly sensitive to the fluorine content, an increase of fluorine content from 2·5 to 4% causing a change from a clear glass to a dense opal.

R. J. Callow & G. Lawson