Why Is My Pottery Glaze Crawling? (And How to Prevent It)

You open the kiln and find bare islands of clay with glaze pulled back around them like ice floes. That is crawling, and it is one of the most demoralizing glaze faults for beginners.

The good news: crawling usually has clear causes, and most of them are fixable with cleaner habits before the next glaze day.

What crawling looks like

Crawled glaze pulls away during drying or firing, leaving exposed clay patches. Edges of the glaze islands often look thickened or beaded.

It can show up as:

• Small bare freckles
• Larger bald spots on rims or handles
• Sheets of glaze that seem to have slid away from a dusty area

If you want a side-by-side mental model of related faults, start with Crawling and Crazing: What Went Wrong.

The most common causes

Dust, oil, or kiln grit on bisque

Glaze needs a clean surface to grip. Finger lotion, dusty shelves, and kiln wash flecks are classic troublemakers.

Prevention: Inspect bisque in good light. Wipe with a barely damp sponge and let it dry fully. Practice Inspect Bisqueware for Defects.

Glaze applied too thick

A thick coat can crack as it dries, then crawl as it melts. Layering heavy on heavy raises the risk.

Prevention: Follow studio thickness guidance. Compare coats with the habits in How Many Coats of Glaze Should You Actually Use?.

Glazing damp or greasy bisque

Moisture and grease fight adhesion.

Prevention: Bisque should feel room-temperature dry, not cold-damp. Keep food, lotion, and dirty towels away from pieces about to be glazed.

Hard-spot wax mistakes

Wax resist is your friend on feet. It becomes a problem when it smears onto walls or when drips create accidental resist zones.

Prevention: Apply wax carefully and let it dry. Clean accidental smears before glazing. Refresh your technique with Applying Wax Resist Correctly.

Soluble salts or odd bisque surfaces

Some clays and firing quirks leave surfaces that glaze does not love. Beginners meet this less often than dust and thickness, but it exists.

Prevention: Ask your studio about the clay body. Test new clays on tiles before a big set.

Application that traps air or weak bonds

Double-dipping without care, brushing over powdery undercoats, or layering incompatible materials can encourage lift-off.

Prevention: Stir well, apply with intention, and test new stacks on tiles. See Pottery Glazing for Beginners for a clean session flow.

A crawl-prevention checklist

Use this before every glaze session:

• Bisque is clean and fully dry
• Foot wax is where you want it, nowhere else
• Glaze is fully stirred, not just surface-mixed
• Thickness matches a known good test
• Overlaps stay thinner than ego wants
• Pieces dry before hard handling

Quick triage when you still get crawling

1. Note where it happened (rim, handle join, flat wall, foot-adjacent)
2. Check whether that area was dusty, thick, or wax-contaminated
3. Make a corrective test tile with cleaner prep and thinner application
4. Log the fault and the fix

Practice naming faults with Identify Glaze Faults on Fired Pieces. Accurate names make better notes.

Related defects (briefly)

Crawling is not the only surface surprise. Two neighbors show up often:

Crazing

Crazing is a network of fine cracks in the glaze glass, often from glaze and clay expanding and contracting at different rates. The glaze stayed on the pot. It cracked like ice on a puddle.

Fit and clay/glaze matching matter here more than dust. Still worth learning beside crawling in Crawling and Crazing: What Went Wrong.

Pinholing

Pinholes are tiny craters or pits. They can come from dust, organic burnout, thick glaze, or firing issues that leave gases escaping late.

They look different from crawling’s bald islands. Dig into Pinholes: Tiny Craters, Big Frustration when your surface looks more like a bubble map than ice floes.

What not to do in panic

• Do not keep piling thicker glaze over a crawled area and refiring as a first move
• Do not sand toxic glaze dust without proper PPE and studio rules
• Do not assume every bald spot is “bad glaze chemistry” before checking cleanliness and thickness

Many beginner crawls are process, not destiny.

Build confidence with tests, not hope

If a combo crawled once, prove the fix on glaze test tiles before you re-glaze a matching dinner set. Thin, clean, documented tests beat heroic kiln prayers.

Takeaway

Crawling is usually a grip problem: dirty bisque, damp ware, wax smears, or glaze that dried too thick to stay put. Clean carefully, wax precisely, apply with measured thickness, and keep notes. Related faults like crazing and pinholing have different looks and different fixes, so name the problem before you chase the solution.