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Defect · Glaze firing
Slumping
Also called: collapsing, deformation
Form loses its vertical structure during firing, leaning or collapsing.
- Appears at
- Glaze firing
- Severity
- Structural
- How common
- uncommon
Causes
Most likely
- ·Clay body fired beyond its vitrification point
- ·Walls too thin to support height at peak temperature
- ·Uneven shelf support
Prevention
- ·Fire within the clay body's rated cone range
- ·Design tall forms with adequate wall thickness
- ·Use level, well-supported kiln shelves
Can it be fixed?
Not reliably — this one is prevented, not repaired. A cracked or bloated pot is a test tile now.
Related defects
Questions
- Why does slumping happen?
- Most often: Clay body fired beyond its vitrification point. Other causes: Walls too thin to support height at peak temperature. Uneven shelf support..
- Can slumping be fixed?
- Not reliably once it has happened; the fix is upstream, in prevention.
- How do I prevent slumping?
- Fire within the clay body's rated cone range. Design tall forms with adequate wall thickness. Use level, well-supported kiln shelves.
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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Claybench can read a photo of the pot against this same reference and rank the likely causes for your clay, glaze and firing.