Evaluation of borax solid wastes in production of frits suitable for fast single-fired wall tile opaque glass-ceramic glazes

Zircon (zirconium silicate, ZrSiO4) is the main opacifier of glossy, opaque, white-coloured, frit-based wall tile glazes. However, zirconia containing frits employed in the preparation of these glazes raise the production cost limiting zircon usage as a raw material at an industrial scale. Therefore, there have been several searches on seeking for alternative frit compositions with lower or without zirconia content. Consequently, positive outcomes were recently reported. With the present study, 1.5-5% of borax concentrator waste replaced certain level of acid boric for B2O3 content in a low zircon containing frit recipe. It is confirmed that waste contribution did not distort the surface properties of the fast single-fired wall tile opaque glazes. Zircon was found to be the main crystal phase of the glazes in laboratory trials. Industrial applications revealed that shorter firing cycles lead to zircon and petedunnite (CaZnSi2O6) formation in the CW-4 glaze.