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Defect · Glaze firing
Underfired glaze
Also called: immature glaze
Glaze surface is rough, dry, matte when intended to be glossy, or easily scratched.
- Appears at
- Glaze firing
- Severity
- Affects function
- How common
- Common
Causes
Most likely
- ·Firing did not reach the glaze's maturation cone
- ·Firing reached peak but cooled too quickly
- ·Kiln temperature uneven; piece was in a cool spot
Prevention
- ·Calibrate kiln with witness cones
- ·Distribute forms away from cool zones (typically kiln floor corners)
Can it be fixed?
- ·Refire to the correct cone
Materials involved
Glaze materials whose chemistry sits behind this defect — each links to its reference page.
Related defects
Questions
- Why does underfired glaze happen?
- Most often: Firing did not reach the glaze's maturation cone. Other causes: Firing reached peak but cooled too quickly. Kiln temperature uneven; piece was in a cool spot..
- Can underfired glaze be fixed?
- Sometimes. Refire to the correct cone.
- How do I prevent underfired glaze?
- Calibrate kiln with witness cones. Distribute forms away from cool zones (typically kiln floor corners).
Sources. Compiled from Claybench's defect reference — the descriptions, causes and remedies that appear consistently across standard ceramics references and studio practice; no single source. It is the same reference the photo diagnosis tool reasons over. Where the Wikibooks Ceramicware Defects Handbook covers a defect it is linked above.
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