Influence of kaolin to temperature characteristics of ceramic glaze

Abstract

Inorganic additives are often added to adjust the rheological properties of the ceramic glaze suspensions. However, additives will change the chemical compositions of the ceramic glazes and thus their temperature characteristics, including melting temperatures. The most common glaze suspensions are a mixture of frits and kaolin. The kaolin is used as an anti-thixotropy agent to regulate the rheology of the glaze suspensions. However, the kaolin contains aluminum oxide (Al2O3) and silica oxides (SiO2), which will change the properties of the ceramic glazes, especially their melting temperature. Studying the influence of kaolin on the melting temperature range of ceramic glazes is always a task that ceramic factories often have to perform. In the methods of studying glaze melting temperature, using heating microscopy (HM) to study the continuous change of glaze with firing temperature by analyzing image data gives quick information quickly and brings high economic efficiency. In this study, based on data analysis obtained from HM, the authors proposed an empirical equation to determine the melting point of glaze depending on the chemical composition of added kaolin with a different concentration in the range of 6 - 12% (6, 8, 10, 12% by mass composition). An empirical estimation is also given that each percent (%) by weight of kaolin will increase the melting temperature of ceramic glaze by 2°C. The research results are a premise for the application of HM to investigate thermal properties such as flocculation temperature, softening temperature, spherical temperature, hemisphere temperature, and melting temperature of glaze and bone ceramic.