The Decolorizing of High Iron Containing Soda-Lime Silicate Glass by Annealing Process

Abstract

The tableware soda-lime silicate glasses, contained with 0.06 wt% of iron oxide, which were annealed at different times and temperatures, were investigated by UV-Vis spectroscopy. The glasses were produced from high iron sand. The iron content was twice as high in the glasses as it is in normal tableware glasses. The redox reaction of iron around glass transition temperature, Fe2+(green) ↔ Fe3+(yellow), was found in the annealing process, according to the redox reaction of iron with polyvalent ions in the glass, nFe3+ + Ma+ ↔ nFe2+ + M(a+-n) where M is the polyvalent ion in glass. In this study, the glasses were prepared by melting in a platinum crucible. After casting, they were annealed with variable times and temperatures. The results of color in CIE L*a*b* system and Fe2+/Fe3+ ratio of glasses showed the effect of the annealing process on the redox reaction of iron. The decolorizing was found during the annealing process. The results of this work led to the method for controlling the effect of iron oxide in the glass and the possibility to use high iron sand to produce tableware glasses.Tableware glass, Iron oxide, Redox reaction, Decolorizing