Bubble Removing from Lead Silicate Glass Melts

In melting process of lead silicate glasses containing 70 wt% PbO, the bubble size distribution, and the manner of formation and elimination of gas bubbles of glass melt at different temperatures and times were investigated. The lead silicate glass was manufactured by melting, fritting and milling of glass powder for several stages. At first, 50 grams of lead silicate glass powder was poured into each alumina crucible for maintaining the batches separately at temperatures of 900, 950, 1000, 1050 and 1100˚C for 15, 30 and 45 minutes, to study the effects of time and temperature on the bubble nucleation, growth and ascension from the lead silicate glass melt. Because of the dissolution of air molecules inside the glass melt and owing to the achievement of super-saturation, gas bubbles were nucleated and grown. Due to the density of the gradient between the gas bubbles and glass melt, the bubbles ascended to the surface of the melt where they ruptured afterwards. The density of alumina crucibles and the glass inside them were measured. The volume and the mean value of the diameter of bubbles were determined by images from the lateral cross section of glass inside crucibles and from the images taken from the surface of the bubbly glassy layer on the surface of the samples.