Influence of water dissolved in the structure of soda-lime-silica glass onmelting, forming and properties: state-of-the-art and controversial issues

The paper summarizes the information available about the water content of s oda-lime-silica glass, the factors that influence it and the influence exer ted by water in glass on redox and sulphur retention, on fining, on the mel ting and forming behaviour, workability and the physical and chemical prope rties of the melt. Such issues were discussed by the authors in their prese ntations at the first Forum on Water in Glass, organized in 1997 by Technic al Committee 14 (TC 14 "Gases in Glass") of the International Commission on Glass (ICG). The present paper reports the conclusions of the final discus sion, highlighting the issues on which consensus was reached (IR spectrosco py is suitable to monitor the water content; the water content of conventio nally fired containers is 300 to 400 ppm and daily oscillations are moderat e; water, redox and sulphur interact mutually; water lowers the viscosity; the influence of water content variations on the radiative thermal conducti vity is moderate) and the still controversial issues (influence of water an d hydroxides in the batch on the final water content; influence of water in the batch and atmosphere on the redox state of the glass; influence of osc illations of OH level on the workability; influence of OH level on ease of forming, product quality and strength).