Underfired

Underfired is a term used primarily in ceramics and pottery to describe a piece that has not reached the intended temperature during firing, or has failed to reach glaze maturity. It can apply to the ceramic body, the glaze, or both. Underfired ware often appears porous, soft, or chalky, with a dull surface and weak glaze adhesion. Colors may be washed out, and the ware may be susceptible to water absorption and damage from handling.

Causes include insufficient kiln temperature or dwell time, an inadequate soak period, incorrect or incompatible glaze formulations, or kiln equipment issues that prevent reaching the target temperature. Other contributing factors can be the size or thickness of the piece, uneven heating, or incorrect firing schedules.

Remedies involve refiring the ware to the correct peak temperature with adequate soak, ensuring the glaze reaches maturity and is compatible with the body, and verifying kiln performance and temperature readings. Potters may adjust firing schedules, revise glaze recipes, or change firing techniques to avoid recurrence. In some cases, separate bisque and glaze firings are used to optimize results.

In contexts outside ceramics, underfired is not a widely used technical term and is seldom applied to other materials. It is generally contrasted with overfired or vitrified conditions, which indicate excessive temperature or complete glaze maturation, respectively.