The Effects of Viscosity and Density on the Bubble Removing from Lead and Soda-Lime Glass Melts

In this work, the bubble removing from lead silicate glasses containing 70% PbO in different time durations and temperature conditions is compared with that of the ordinary soda-lime glass. Batches of lead glass powders weighing 50gr inside alumina crucibles were heat treated at 900, 950, 1000, 1050 and 1100˚C for time durations of 15, 30 and 45 minutes. A sample of soda-lime glass was heat treated at 1400˚C for 5 hours and poured in a steel mold. The effect of viscosity and density of melt on the rate of bubble ascending inside lead silicate and soda-lime silicate glass melt are discussed. By using the data of the total density of glass (glass containing bubble), the density of glass without bubble and the mean bubble size measurements, the total volume of the bubble and the variation of the volume and the number of the bubbles at different time durations and temperatures were determined. The rate of bubble removing in lead silicate glass is affected by the thickness reduction of the bubbly layer on the surface of the melt, then the bubble number reduction rate of the bubbly layer at different time and temperatures was considered as the kinetics of bubble removing.