The use of pumice (pumicite) in transparent roof tile glaze composition

In this study, the use of pumice as an alternative fluxing agent instead of Na-Feldspar in the transparent roof tile glaze composition was investigated. The experiments were designed as a mixture experiment. According to heating microscope results, pumice was observed deforming at 850 °C and flowing at 1270 °C. Considering the properties of the pumice it is possible to use it in raw glaze (without using frit) applications instead of feldspar. Colour, brightness and hardness values of fired samples were measured. These data were analysed with MINITAB 13.0 statistical software programme. Microstructure of glaze/tile interfaces of single fired samples was studied by using a scanning electron microscope (SEM). The use of pumice in the glaze composition showed no negative effect on the colour, brightness and hardness values and decreased the flowing temperature of the glaze. It was concluded that pumice could easily replace Na-Feldspar as an alternative fluxing agent in appropriate proportions in such kind of a roof tile glaze composition without causing undesired consequences.