VISCOSITY MEASUREMENTS IN GLASS1

Abstract
The concentric cylinder method, described in a previous paper, has been used in the measurement of viscosities in molten glass. The apparatus and method of measurement are fully described. Comparisons are made between results obtained and those of English, Stott, and Washburn. Quite good checks are found in comparisons with English and with Stott, but results obtained in comparing with Washburn indicate a difference supposedly due to his use of a variable calibrating factor. Measurements made by the use of a falling sphere give values of viscosity 25 to 50% higher than those given by the concentric cylinders in the same glasses. This may be due to the extended extrapolation of Ladenburg's correction for finite boundaries.