Crazing and shivering are opposite sides of the same coin: glaze fit. Both come from a mismatch between how much the glaze and the clay body expand and contract with heat. Understanding the difference tells you exactly which direction to adjust your glaze.
| Defect | What happens | Root cause |
|---|---|---|
| Crazing | Fine cracks web across the surface | Glaze expansion too high (glaze in tension) |
| Shivering | Glaze flakes or pops off edges | Glaze expansion too low (glaze in compression) |
When the glaze shrinks more than the body on cooling, it's stretched until it cracks: crazing. When the body shrinks more than the glaze, the glaze is squeezed until it buckles and flakes: shivering. A little compression is actually ideal, which is why crazing is far more common than shivering.
Crazing is a functional and hygiene problem. Shivering is a safety problem. The slivers that pop off edges and rims are small, sharp, and can end up in food or drink. If you see shivering on functional ware, pull those pieces from use immediately.
The key mental model: you're not fixing the glaze or the body alone, you're tuning the fit between them. The same glaze can craze on one clay and fit perfectly on another. That's why a recipe that works beautifully for one potter fails for another using a different body.
Any time you pair a new glaze with a new body, fire a test tile first and check it over the next few days. Crazing sometimes shows up hours or even weeks after the firing as moisture works into the body, so give a pairing time before you trust it on a whole batch.
Consistent, even firings make glaze fit far easier to diagnose. If your kiln is firing unevenly or you're ready to upgrade, call or text me, Spencer, at (801) 839-5882.
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