Crazing on a Donabe: Why the Fine Lines Are Normal
Last updated: 29 August 2026
Fine lines appear on a donabe with use. They spread across the glaze in a web, they get more visible over the years, and they are the single thing customers contact us about most often. They are normal. This guide explains what they are, why they happen, and — the part that actually matters — how to tell them apart from a crack that means the pot is finished.
Our specialist, Kai, wrote this guide to crazing on donabe. In this guide:
- What crazing is — and why porous clay does it.
- Crazing or crack? — the difference that decides whether to keep using the pot.
- Slowing it down — seasoning and heat control.
What Crazing Is
The network of fine lines is called kannyu. It sits in the glaze, not in the pot body. Japanese donabe are made from porous clay, and clay and glaze expand at slightly different rates when heated. Over repeated heating and cooling, the glaze layer develops a fine crackle while the clay underneath stays sound.
This is a property of the material, not a manufacturing fault, and it is why traditional porous-clay pots craze more readily than modern glazed ones. Our guide to what a donabe is made of sets out how the clay differs between the four classic production regions.
Crazing does not affect how the pot cooks. Warranty claims are not accepted for it, in Japan or here, because it is expected behaviour rather than a defect.
Crazing or Crack? The Difference That Matters
Crazing — keep using the pot: fine lines in the glaze surface only. They form a web or net pattern, feel smooth or barely perceptible under a fingertip, and appear gradually over many uses. The pot holds liquid normally.
A structural crack — retire the pot: a single line running through the body, usually from a drop or from severe thermal shock. You can often feel it as a ridge or catch a fingernail in it. If the pot weeps, seeps or leaks anywhere, stop using it. A cracked clay pot can fail suddenly under heat.
The simple test: fill the pot with water and leave it on a dry benchtop for an hour. Crazing holds water. A structural crack does not.
Slowing It Down
You cannot prevent crazing, but two habits keep it slow and keep the pot sound for years.
1. Season a traditional pot before first use
Traditional porous-clay donabe are seasoned by cooking a simple rice porridge (okayu) in them. The starch settles into the clay's pores and seals them, which strengthens the pot and stops food odours soaking in. This step is called medome.
Modern glazed donabe are fired to a non-porous surface and many do not need it — follow the instructions supplied with your pot, or see our donabe user guide for the method.
2. Avoid thermal shock
Sudden temperature change is what turns ordinary crazing into a structural crack. Never put a hot pot into cold water, and never put a cold or wet pot onto high heat. Heat gradually, and let the pot cool completely before washing.
A donabe also holds heat long after it leaves the stove, so it will mark a plastic or timber benchtop. Rest it on a donabe base or pot holder — all sizes fit every pot in the range.
About the Author
Authored by our specialist, Kai, a product specialist at My Cookware®. We review this guide as the range changes.
If you have any follow-up questions, email us at hello@mycookware.com.au or use the chat box on this page. Our friendly team will respond as soon as possible.
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