Development of temmoku glazes and their applications onto different tiles under industrial fast firing conditions at 1180 °C

Abstract

Temmoku glazes are special and artistic glazes that are used in certain applications. Temmokus are either slip glazes made from ferruginous clay or feldspathic type glazes containing iron oxide. Glaze composition, clay body, application method, and firing regime are the most important factors for achieving these kinds of glazes. In this study, a new temmoku glaze composition was developed and applied on floor and porcelain tile bodies, respectively. Industrial fast firing processes were conducted at Altin Seramik Factory at 1185 °C. All of the glaze surfaces were smooth and glossy after industrial fast firing. Color of the glazes was black metallic with an oil spot effect. L*a*b* values were measured by a spectrophotometer. Final surfaces of the temmoku glazes were visualized by polarized optical microscope and characterized by an X-ray diffractometer (XRD), scanning electron microscopy (SEM), and energy dispersive x-ray (EDX). Generally, temmoku glazes displayed lower L* values on both floor tile and porcelain bodies. According to the compositional modifications, adjusting the SiO2/Al2O3 ratio was critical and the maximum Fe2O3 content should not exceed 5%. This study showed that various visual effects are related with different crystal morphology of quartz, magnetite, maghemite, and hematite and that the microstructure has an important effect on color and appearance of temmoku glazes.