The high-hardness ceramic glazes based on basalt from Bali Province for ceramic body coatings

Abstract

The ceramic glaze method is not only done to add color aesthetics but also to increase the hardness of the glaze. Basalt is one of the raw materials developed as a ceramic glaze material because it is cheap, easy to find, and has good characteristics. This research aims to determine glaze characteristics by varying the concentration of basalt rocks from the Ababi area, Karangasem Regency, Bali Province. The experiment used basalt at 45%-61%, Feldspar 27%-37%, Kaolin 3%-8%, and ZnO 7%-10% as raw materials for glaze, not frit glaze. Heating the glaze material layer at 1,250 °C for 3 hrs. The product characteristics of glaze ceramics include chemical composition, crystal phase, microhardness, porosity, density, thermal expansion coefficient, and surface morphology. Basalt from Bali is characterized by its high Fe2O3 content, reaching 20.07 wt%. Compared to basalt in generally, it has a different impact on the physical and mechanical characteristics of the ceramic glaze produced. Based on the observation of ceramic glaze products, the glaze composition with 56% basalt, 32% feldspar, 5% kaolin, and 7% ZnO showed the best coating, with a yellowish-brown color and an average thickness of 79.82µm. The hardness value of the glaze layer is 6.5 GPa, exceeding the standard hardness value of glazes on the market. Glazed ceramics contain the minerals Gahnite (ZnAl2O4) and Coesite (SiO2), which can increase the hardness of the glaze. This research demonstrates the tremendous potential and added value of using basalt from Bali Province as a raw material for glazed ceramics.