Water content of sulfate-fined industrial soda-lime glass and its influence on workability

Abstract

The aims of the paper are: a) to systematically determine by IR spectroscopy the water content of sulfate-fmed industrial soda-lime glass (mainly Container and float, besides that household and technical glass) produced in Italy; b) to highlight the influence of redox State , melting conditions, batch and cullet addition on the water content; c) to check the consistency with time and between different feeders of the water content in the glass produced by a given furnace; d) to assess possible correlations between water content and workability in Container glass. The water content ranges between 300 and 400 ppm in conventionally fired glass, with electrical melting it decreases to 150 to 200 ppm, with oxycombustion it increases to 500 to 600 ppm. In the case of conventional flame melting the main factor influencing the water content is the redox State , due to a water/sulfate exchange. When a glass with a given color and redox State is produced in a given furnace, the daily oscillations of the OH level are moderate, with negligible effects on viscosity. In all the workability problems analyzed the contribution of water content oscillations was negligible as compared to other factors. According to the results obtained, significant water-related viscosity variations are expected to take place only when the meldng atmosphere or the redox conditions are significantly altered.