Feldspar

Potash feldspar (K₂O) produces a more viscous glass phase during firing, resulting in higher strength and better surface quality, and is preferred for sanitaryware and premium tableware. Soda feldspar (Na₂O) produces a less viscous glass, promotes faster vitrification, and is suitable for fast-firing tile bodies.

In ceramic glazes, feldspar provides the alkali fluxes (K₂O and Na₂O), alumina (Al₂O₃), and silica (SiO₂) needed for glass formation. It controls glaze melt viscosity, surface tension, and thermal expansion, contributing to smooth, defect-free glaze surfaces.

In sanitaryware, potash feldspar ensures complete vitrification of the dense porcelain body at the firing temperature, providing the mechanical strength, water absorption resistance, and bright glaze surface required for premium vitreous china sanitaryware.

Yes. The feldspar content directly controls the onset and extent of vitrification. Higher feldspar loadings lower the effective firing temperature and increase glass phase formation, which improves densification but can also cause deformation if excessive — requiring careful formulation control.

For ceramic body applications, feldspar is typically milled to below 63 microns (240 mesh) to ensure uniform distribution and reactivity. For glaze applications, finer milling (below 45 microns) is preferred for consistent glaze surface smoothness and chemical homogeneity.