Determinations Of The Viscosity Of Glass

A method has been developed for measuring the viscosity of glass over a considerable range of temperatures, with the object, amongst others, of correlating the results with the lamp-working properties, particularly the "working range" of different glasses. Results of measurements are given for four samples of glass and an application is made to the determination of suitable annealing temperatures. Heating curves of the same glasses have also been obtained, and in each case a retardation in the rate of rising of temperature has occurred about the softening point. For the four rather similar glasses examined, the temperatures at which this effect has its maximum intensity are temperatures of equal viscosities.