Effect of SiO2/Al2O3 ratio on the whiteness of ceramic tile engobes with low zircon content.

Micronized zircon (ZrSiO₄) is used as an opacifier in the production of engobes, opaque glazes, and floor tile bodies. Elevated price levels incentivize researchers to develop alternative engobe formulations with reduced zircon ratios. In this study, new engobes with low zircon content were developed with varying SiO₂/Al₂O₃ mixtures. The effect of the SiO₂/Al₂O₃ ratio on the performance and opacity of the wall and floor tile engobes was investigated. It has been observed that the amount of zircon in the sample compositions could be reduced up to 40% by optimizing the refractoriness-water absorption balance of the engobe with the SiO₂/Al₂O₃ ratio while keeping the opacity in the preferred levels. The color difference (E) value relative to the standard surface was below 1, which is acceptable for visual perception for all the samples. Other measurements such as water absorption and firing shrinkage of the floor tile samples were found to be compatible with the standard composition. [ABSTRACT FROM AUTHOR]