Feldspar

Description

Feldspars comprise a significant group of aluminium tectosilicate minerals that constitute a major portion of the Earth's crust, incorporating cations such as potassium, sodium, calcium, or barium. Within the ceramic industry, these crystalline minerals function primarily as essential fluxing agents. During firing, feldspar undergoes melting to facilitate the vitrification of ceramic bodies, acting as a glass-forming binder that unites refractory particles into a consolidated matrix. In glaze chemistry, they are valued for their ability to promote the formation of durable glass surfaces at medium to high temperatures. The category is broad, but the most prevalent types utilized in ceramic formulations are alkali feldspars (such as orthoclase) and plagioclase (the sodium-calcium series). While feldspar is a vital source of K2O and Na2O, which can enhance glaze brilliance, its high alkali content may induce significant thermal expansion, potentially resulting in crazing. Consequently, technicians must balance feldspar additions with materials that introduce low-expansion oxides—including MgO, CaO, Li2O, SrO, or BaO—to manage the physical stability of the fired product. Feldspar concentrations typically range from approximately 15% in stoneware bodies to as much as 50% in porcelain compositions.