Predicting sintering behavior of syenite-based porcelain tile compositions with alternative fluxes

Reducing energy use, emissions and reliance on critical feldspar has increased interest in alternative and secondary fluxes for porcelain tile manufacturing. However, the ability of liquid-viscosity models to predict firing temperatures in partially crystalline bodies remains uncertain. Fluegel and Giordano were applied to estimated vitreous-phase compositions of syenite-based bodies containing perlite, spodumene, frits, fly ash, glass waste and boron residue, and predictions were compared with experimental optimum firing temperatures. Giordano was more accurate for most of the formulations studied. As an exploratory extension, Giordano was coupled with Krieger–Dougherty to represent the effective viscosity increase caused by fine mullite (<5 µm) potentially suspended in the melt. This reduced RMSE from 17.87 to 11.31 °C and MAE from 13.97 to 9.03 °C. Although the correction did not describe all formulations and requires future validation, the framework can accelerate screening and support resource-efficient design.