Annealing Of Flat Glass

The mechanical concept of the annealing process advanced by Adams and Williamson and the structural concept of Lebedev are discussed. D prefers the latter which considers birefringence only as the net result of density changes corresponding to variations in structural state and not as the sole criteria for annealing. Changes in density and refractive index of quenched vs annealed glasses are both subject to two effects opposite in direction but in the case of density the net effect is a greater percentage change than in the case of refractive index; therefore density measurements are preferred.