FOAMING IN GLASS MELTS PRODUCED BY SODIUM-SULFATE DECOMPOSITION UNDER RAMP HEATING CONDITIONS

Ramp heating a glass batch with sulfate permits determination of the foaming temperature and maximum foam height as a function of sulfate addition. Experiments revealed that, in the soda-lime glass studied, foam was produced when the mass fraction of SO3 in the glass was higher than 0.0027. With increasing sulfate content, the foaming temperature decreased and the maximum foam height increased until the mass fraction of SO3 was 0.01. Further additions of sulfate had little effect on foaming temperature and decreased maximum foam height. The results are discussed in terms of sulfate solubility and nonequilibrium effects.