Thermal‐Gradient‐Induced Migration of Bubbles in Molten Glass

Buoyant fining of molten glasses does not occur in a weightless environment. One method suggested for fining is to apply a temperature gradient to cause bubbles to move because of the surface tension temperature dependency. Ground-based experiments were conducted to demonstrate that thermal migration actually occurred in glassmelts and to estimate the magnitude of the effect. Thermal migration, consistent with theory, was found in borax melts, evidencing an approximately linear relation between bubble diameter and bubble velocity for a given temperature and gradient. Other effects, such as near-bubble interaction, were also observed.