# How to Prevent Glaze Crawling

Source: https://potterynest.com/blog/glaze-crawling-causes-and-fixes
Published: 2026-09-13
Publisher: Pottery Nest

Crawling happens when glaze pulls away from the clay during firing, leaving bare patches of clay surrounded by thick, rounded beads of glaze. It can ruin a favourite piece and is especially frustrating because the glaze looked fine before it went into the kiln. Most crawling starts before firing, with dust, oils, thick application or glaze that shrinks and cracks as it dries.

## What crawling looks like and why it happens

Crawled glaze forms islands and ridges with exposed clay between them, often with rolled, rounded edges. It happens when the glaze layer loses contact with the bisque surface before or during melting, and surface tension pulls the molten glaze into beads.

The weak bond usually forms long before the firing. Anything that stops glaze adhering, or anything that makes the dry glaze layer crack, gives the glaze a place to pull back once it starts to melt.

## Clean the bisque ware

Dust, kiln wash flakes and oils from your hands prevent glaze from bonding to bisque. Handle bisqueware with clean hands and wipe pieces with a damp sponge before glazing, then let them dry briefly.

Avoid applying hand lotion before glazing, and store bisque ware covered so dust does not settle on it. Wax resist dripped accidentally onto areas you intend to glaze also causes bare spots.

## Apply glaze at the right thickness

Thick glaze layers shrink more as they dry and are more likely to crack, which leads to crawling. Glazes with high clay content or high shrinkage are especially sensitive.

Follow manufacturer guidance on coats or dipping time, and check thickness by scratching a small area with a needle tool. When layering glazes, keep the total thickness reasonable and test combinations on tiles before using them on finished pieces.

## Watch for cracks in dry glaze

If dry glaze shows fine cracks before firing, those cracks often become crawled areas. Rub cracks gently with a fingertip to close them, or wash the glaze off, let the piece dry thoroughly and reapply.

Glazes that crack on drying may contain too much raw clay or need adjustments. Adding a small amount of glaze binder or gum, or calcining part of the clay in the recipe, can reduce shrinkage for those mixing their own glazes.

## Dry pieces before firing

Glazing bisque that is still damp from rinsing, or loading freshly glazed pieces into a kiln before they dry, traps moisture. Steam can lift glaze from the surface as the kiln heats.

Let glazed pieces dry fully, often overnight, and consider a slow initial heating segment in the firing schedule. This is especially important for thick glazes and pieces with multiple glaze layers.

## Repairing crawled pieces

Small crawled areas can sometimes be repaired by warming the piece, applying glaze mixed with a little binder to bare patches and refiring. Results vary, and refiring may change the appearance of the rest of the glaze.

For functional ware, make sure repaired areas are fully sealed and food-safe glazes are used. Document what caused the problem so you can adjust future glazing.

## Related buying guides

- https://potterynest.com/best/best-dipping-glazes
- https://potterynest.com/best/best-pottery-glazes
- https://potterynest.com/best/best-pottery-sponges