SULFATE MASS-BALANCE AND FOAMING THRESHOLD IN A SODA LIME GLASS

A semiempirical equation relating the foaming temperature to sulphate concentration was established. Literature data on sulphate solubility and melt viscosity and the variation of foaming temperature with sulph ate concentration obtained in a previous study were used to evaluate e mpirical coefficients involved in the equation. An agreement between t heory and experiment was attained when bubble nucleation on undissolve d silica grains and nonuniform distribution of SiO2 within the melt we re considered. The results show that the rate of dissolution of solid grains in the melt and the temperature history control sulphate foam f ormation and retention in glass.