Bubble generation at glass/refractory interfaces: A review of fundamental mechanisms and practical considerations

Abstract

Fewer point defects, especially fewer bubbles, have become a principal requirement in meeting improved quality standards for many commercial glass products. Many of these defects may be bubbles generated from the interaction of refractories with the molten soda-lime-silica glass. Porosity of the refractories is an obviously important factor: under some conditions thermal transpiration may become a mechanism. In fused-cast refractories, exudation of vitreous phases likely leads to bubble formation, and ZrO2-containing bodies have the potential for supporting electrolytic mechanisms. Specific refractory impurities, e.g., nitrides and iron species, also generate bubbles in contact with the melt. Interactions between molten glass and refractories are best characterized by tests that use a covering atmosphere typical of actual service. Long enough equilibration times are necessary to document transient behavior and steady-state conditions.