Crawling is the defect where glaze pulls away from the clay during firing and beads up like water on a waxed car, leaving bare patches of exposed body. It looks dramatic, but the causes are almost always mechanical, and most of them come down to what happened before the piece ever went in the kiln.
At its core, crawling is a bond failure. Either the glaze couldn't grip the surface (contamination) or it shrank and cracked before firing and then pulled those cracks open in the kiln.
| Fix | Why it works |
|---|---|
| Sponge bisque, dry overnight before glazing | Removes dust and oils so glaze can grip |
| Thin the glaze / apply less | Thick coats crack and mound up in corners |
| Add a small amount of flux | Helps a stiff matte glaze flow out and re-knit |
| Calcine part of the clay content | Reduces drying shrinkage that leads to cracks |
| Don't fully dry one glaze layer before the next | Prevents separation between coats |
Handle bisque ware as little as possible with bare hands, and give every piece a quick wipe or sponge before glazing. Skin oils are invisible and they're the number-one cause of crawling that potters never diagnose. Matte glazes are more prone than glossy ones, so if you love a matte recipe that keeps crawling, a touch more flux is usually the answer.
From kilns to shelves to the accessories that keep your firings clean, I can help you set up right the first time. Call or text me, Spencer, at (801) 839-5882.
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