In the glaze, the melting of quartz, clay, and mullite is fast at high temperatures, and the solubility is large. Albite feldspar powder has a low melting temperature and good transparency. The melting temperature range of soda feldspar is narrower than that of potassium feldspar, the viscosity of the melt at high temperatures is smaller, and the change with temperature is faster.
The melting point of potassium feldspar is 1290°C, that of albite feldspar is 1215°C, and that of barium feldspar is 1715°C. Natural feldspar is often a solid solution, and its melting point is lower than that of single-component feldspar. Wide melting interval is one of the good technological properties of feldspar. For example, it starts at 1200°C and changes to a liquid phase at 1350°C. The melt is transparent and viscous, and the process performance is the best. The melting interval of albite is small, the melt viscosity is low, and it is easy to deform when fired.
Alkaline feldspar has a good fluxing effect. For example, the melting point of kaolinite is 1770°C, and the melting point of quartz is 1713°C. If feldspar is added to the Al2O3-SiO2 system, the liquid phase will begin to appear at 985°C±20°C, and the higher the content of feldspar, the lower the initial melting temperature. At the same temperature, the fluxing effect of sodium feldspar is greater than that of potassium feldspar.
Sodium feldspar glaze is a glaze prepared by using feldspar instead of plant ash as a flux, and it is a kind of transparent glaze. It is characterized by high hardness, bright and transparent glaze, soft feeling, wide firing range (1260-1350°C), high viscosity at high temperatures, not easy to flow, uniform color development, wide source of raw materials, stable chemical composition, suitable for large-scale industrialization Production. Compared with albite glaze, the traditional gray glaze and lime glaze have the disadvantages of narrow firing range, low viscosity at high temperatures, high fluidity, complex raw material sources, and poor chemical stability. Especially since modern times, the sources of fuel used by people have undergone major changes, and coal, oil, and natural gas have gradually replaced firewood and forage, resulting in increasingly tight sources of plant ash. After people understand the characteristics of albite, a good substitute for plant ash, they can no longer do without it.
