Surface Tension of Molten Glass

Abstract

The surface tensions of a number of different glasses have been determined by a new method. The method is termed ``The Bulb Method'' and is similar to the soap bubble experiment in which the excess of pressure within the bubble can be balanced against a small head of liquid in a manometer. The weight of the glass bulb is taken into consideration. The method is applicable to a temperature range of approximately 200°C above the annealing point of the glass. The variation of surface tension with change in temperature over the upper range of temperature investigated is found to be of the order of 0.04 dyne per cm per degree C. The magnitude of the surface tension for this range varies from 230 to 360 dynes per cm depending upon the kind of glass. A survey of previous results on surface tension discloses values of widely different magnitudes. One group of experimenters has obtained values of the order of 150 dynes per cm and another group, values of approximately 400 dynes per cm. The results obtained by the bulb method fall approximately midway between the values obtained by previous experimenters.