glazury

Glazury are vitreous coatings fused to ceramic bodies during firing, forming a glassy surface that is normally smooth, impermeable, and decorative. They serve functional purposes such as water resistance and chemical durability, and also provide color, texture, and gloss. Glazes are applied as suspensions or slips before firing and melt to form a durable ceramic glaze layer.

Glazes are composed mainly of silica as a glass former, with fluxes that reduce the melting temperature, stabilizers such as alumina, and colorants like metal oxides or spinels. Common glaze families include transparent glazes, opaque white glazes (often tin-based), and more decorative or matte glazes. Modern glazes frequently use frits to improve consistency and safety.

Application and firing: Glazes are applied to bisque-fired forms by dipping, pouring, brushing, or spraying. After drying, pieces are fired in a kiln to a specific cone range, depending on the glaze and body. Firing temperature, atmosphere, and cooling rate influence final color, gloss, and texture. Some glazes crystallize during slow cooling for decorative effects.

Types and characteristics: Historically important glazes include lead glazes and tin glazes; contemporary ceramics often use alumina-rich glazes or feldspathic systems. Color development depends on oxides such as copper, cobalt, iron, and manganese, with different results under oxidation or reduction.

Defects and safety: Common glaze problems include crazing, pinholing, crawling, and blistering, usually caused by mismatches in glaze and body or application issues. Lead-containing glazes are restricted in most jurisdictions due to health risks; modern glazes avoid lead, using alternative fluxes and frits. Good practice includes lab testing and proper disposal of waste.