In tile and ceramic industry, frits are used for producing opaque and glossy glazes. Commonly used frits are prepared by using opacifiers such as ZrO₂ and TiO₂, but the high price of these raw materials leads to a higher cost of the final product. In this research, an opaque frit containing in-situ synthesized Wollastonite (CaSiO₃) and Diopside (CaMgSi₂O₆) was developed as a substitute for Zircon-containing frits. By choosing optimized proportions of oxides in the frit composition, sufficient crystallization occurred in MgO-CaO-Al₂O₃-ZnO-B₂O₃-SiO₂-K₂O-Na₂O glass ceramic system. XRD, SEM, EDS, STA, and colorimetry (CIELab) tests were used to compare the prepared samples with a reference zircon containing one which is used in tile industry. The results showed that whiteness and glossiness indices of the prepared sample were 73.61 and 86.56, respectively, which are comparable with those of zircon-free reference sample with whiteness and glossiness indices of 77.05 and 89.22, respectively.

Keywords: Glossy opaque frit, Zircon, Diopside, Wollastonite, Whiteness and glossiness indices