Compositional modifications to floor tile glazes opacified with zircon

In the ceramic tile industry opaque glazes with considerable zircon content are widely used. However, the high cost of zircon limits its wide use in relevant glaze compositions. In the present study, a model opaque glaze was modified by changing the alumina/silica ratio, adding potassium oxide, or using a higher content of opaque frit while gradually eliminating the zircon content in the glaze batch. After glaze preparation, application, and single firing of glazed floor tiles under industrial conditions glazes were characterised by XRD, SEM, and EDX. The optimum alumina/silica ratio was found to be 0·26. Colour parameters L, a, and b of starting and final glazes showed that an increase in opaque frit content gives more positive improvement in opacity and in dry abrasion resistance than potassium oxide addition. Removal of zircon from the glazes resulted in a decrease of ∼13–18% in glaze cost without detrimental effect on opacity.