On the Viscosity of Some Glasses in the Annealing Range
JSGT 1945 V29 T414-T427
It is shown that, in the range 1011–1013 poises, the viscosities of some borosilicate glasses take considerable time to become stabilised, whereas those of soda–lime–silica glasses rapidly approach equilibrium values. The viscous properties of the stabilised borosilicate glasses, however, are closely similar to those of the soda–lime–silica glasses. The annealing temperatures of several glasses have been determined optically by observing the temperature at which a rod becomes strain free when heated at a uniform rate of 2° per minute. All the glasses, including the. borosilicates, had a viscosity of about 1013 poises, after 30 minutes heat treatment at their annealing temperatures.
A. E. Dale & J. E. Stanworth
