# Glaze Crawling: Why It Happens and How to Stop It URL: https://myclay.online/blog/glaze-crawling-causes-and-fixes Published: 2026-04-08 Updated: 2026-08-01 Category: Glazing Tags: Glazing, Troubleshooting, Firing Reading time: 5 min > Crawling means the glaze did not wet the surface. Clean the bisque, thin the application, and check for high-shrinkage materials or dusty studio air. Crawling looks dramatic: bare islands of clay with thick, rolled-up beads of glaze around them, as if the glaze deliberately backed away. That is exactly what happened. Molten glaze has surface tension, and if it cannot bond to the clay underneath, it pulls itself into blobs the way water beads on a waxed car. > **From the studio:** I lost a whole shelf of mugs to crawling one winter and blamed the glaze for weeks. It was the studio. I had been sanding [bisque](/blog/clay-stages-leather-hard-bone-dry) on the same bench where I glazed, and every pot picked up a fine film of dust before it ever hit the bucket. A damp sponge, wiped over each pot the same morning I glazed it, ended the problem entirely. So every fix comes down to one question: **what stopped the glaze from sticking?** ## Cause 1: A dirty or greasy bisque surface The most common cause by a wide margin. Fingerprints from carrying bisque, oil from a workbench, dust that settled during the week, or kiln wash that transferred from a shelf. **Fix**: Wipe every bisque piece with a damp (not soaking) sponge and let it dry fully before glazing. Handle glazed-to-be surfaces by the foot or with clean hands. In a shared studio, glaze on the same day you wipe. ## Cause 2: Glaze applied too thick A thick layer shrinks more as it dries and as the binders burn out. If the dried glaze layer cracks before it melts, the melt closes those cracks into beads instead of healing them. **Fix**: Check for dry cracks in the raw glaze before firing — if you can see a crazed pattern in the unfired coat, it will crawl. Thin the glaze, dip for less time, or let the piece dry between coats. Bisque that is very porous (underfired bisque, cone 08) grabs glaze fast and thick; firing bisque a cone higher gives you more control. ## Cause 3: Dusty or over-sanded bisque Sanding bisque leaves fine powder in every pore. That powder is a release layer. **Fix**: Sand, then rinse or wipe thoroughly. Sand outdoors or with a wet method — dry silica dust is a genuine lung hazard, not just a glaze problem. ## Cause 4: High-shrinkage materials in the glaze recipe Plastic clays and colloidal materials shrink hard on drying. Recipes heavy in raw kaolin, ball clay, or bentonite are crawl-prone, especially over 20% total clay content. **Fix**: Substitute part of the raw kaolin with calcined kaolin. Calcined clay has already lost its chemical water, so it does not shrink. Replacing a quarter to a third of the raw clay usually cures a chronic recipe without changing the fired result. ## Cause 5: Glaze over glaze, or glaze over slip Two layers means two shrinkage rates and a weak boundary. Layering is a legitimate technique, but it doubles the [thickness](/blog/how-to-glaze-pottery-at-home) problem. **Fix**: Apply the under-layer thin, let it dry completely, and keep the total thickness at roughly what a single dip would give. Do not layer over a slip that has itself dried and cracked. ## Cause 6: Soluble salts and hard water Some clays and some tap water carry soluble salts that migrate to the bisque surface as it dries, leaving a scum that the glaze will not wet. **Fix**: If you see a whitish bloom on dried bisque, wipe it. Mixing glazes with distilled or filtered water eliminates a whole category of intermittent problems in hard-water areas. ## Diagnosing yours in five minutes 1. **Where is it?** Crawling only on rims and edges points to thick application. Crawling in random patches points to contamination. 2. **Was the raw glaze cracked?** If you did not look, look next time. This one observation splits the causes in half. 3. **One glaze or all of them?** One glaze means the recipe. All glazes means your bisque prep or your studio air. 4. **New bag of anything?** New clay, new glaze batch, new water source, new shelf wash. 5. **Did anything sit around?** A pot glazed and left for three weeks in a dusty studio picks up a fresh dust layer *on top* of the glaze, which also crawls. ## Using it on purpose Crawl glazes — sometimes called lichen or beading glazes — are recipes deliberately loaded with magnesium carbonate or high raw clay content to produce controlled crawling. They are beautiful on vertical surfaces and terrible anywhere food touches, because the beads leave unglazed clay exposed and the texture harbours bacteria. Keep them on the outsides of vases and sculpture. ## Preventing it, rather than diagnosing it Once you know the causes, prevention collapses into a short routine that costs almost nothing. 1. **Wipe every bisque piece** with a damp sponge and let it dry before glazing. This alone removes the single biggest cause. 2. **Handle bisque by the foot** once it is wiped, or with clean hands. 3. **Glaze on the same day you sand.** Sanding dust settles on every horizontal surface in the room. 4. **Sieve glaze that has been standing** for weeks, and stir every bucket right to the bottom before use. 5. **Look at the raw glaze** before the piece goes in the kiln. If you can see a fine crazed pattern in the dried coat, it will crawl. Wash it off and reapply thinner. 6. **Keep total thickness to about one dip**, even when layering. 7. **Use filtered water** for mixing if you are in a hard water area, which removes an entire category of intermittent problems. That routine takes perhaps two extra minutes per firing. Set against a shelf of ruined pots, it is the best trade in the studio. ## Where to go next Most crawling traces back to application, so [how to glaze pottery at home](/blog/how-to-glaze-pottery-at-home) is the practical companion to this post. If the fault is in the recipe rather than your bisque, [how to make ceramic glaze](/blog/how-to-make-ceramic-glaze) covers substituting calcined kaolin. And [what is ceramic glaze made of](/blog/what-is-ceramic-glaze-made-of) explains why high-clay recipes crawl in the first place. ## Frequently asked questions **Can you refire a pot to fix crawling?** Sometimes. Clean the bare area, dab on a thin patch of the same glaze, and refire to the same cone. It works best on small isolated spots; large crawled areas usually crawl again. **Is crawling the same as shivering?** No. Crawling happens during the firing as the glaze melts and pulls into beads. Shivering is glaze flaking off after cooling because the glaze is under compression relative to the body. **Does dust really cause crawling?** Yes, routinely. Any film between glaze and clay — dust, grease, a fingerprint, kiln wash — stops the melt from wetting the surface and it retreats into a bead. --- Source: https://myclay.online/blog/glaze-crawling-causes-and-fixes — https://myclay.online/