glazefire

Glazefire is a term used in ceramics and glass arts to describe the phase of kiln firing when a glaze coating on a ceramic piece begins to melt and fuse into a vitreous layer. It emphasizes glaze maturation within the overall firing sequence, rather than the entire firing itself.

Overview and usage

Glazefire is discussed by potters and kiln operators as the point at which the glaze transitions from a dry powder, slip, or suspension to a continuous, glassy surface. The terminology and emphasis can vary between studios, but the concept centers on glaze behavior during heating, melting, and fusion.

Process and temperature

Glazefire occurs after the bisque stage and during the glaze firing. The exact temperature depends on the glaze recipe and firing system. Low-fire glazes typically mature at cone 04–06 (approximately 1050–1200°C), while high-fire glazes mature at higher temperatures (often cone 8–10, roughly 1200–1280°C or higher). Some glazes require longer soaks to reach full maturity, while others may overfire if held too long.

Materials and reactions

Glazes are mixtures of silica, fluxes, and stabilizers, sometimes with colorants. When heated past their melting point, these components flow and fuse to the ceramic body, forming a glossy, protective, and decorative surface. The appearance can vary with glaze chemistry, firing atmosphere, and even kiln drift.

Observations and outcomes

Proper glazefire yields a smooth, even glaze with the intended gloss, color, and surface texture. Underfired glazes may look dull or opaque; overfired glazes can run, blister, or craze, affecting adhesion and appearance.

Practical considerations

Controlling glazefire involves adjusting firing ramp rates, soak times, kiln atmosphere, and glaze formulations. Documentation of firing curves aids reproducibility and quality control.