Cracks and Character: The Lifecycle of Your Hibachi Grill
Last updated: 14 April 2026
Made from diatomaceous earth quarried on Japan's Noto Peninsula, the konro grill — often called a hibachi grill in Australia — is built for sustained high-heat charcoal grilling. Fine cracks are part of how it lives, not a sign that something has gone wrong.
Our specialist, Kai, wrote this guide with Melbourne chef Roger Young. In this guide:
- Why cracks appear — and why they can show up on the first use.
- Diatomaceous earth — what the material is and what it does.
- Care — the one habit that decides how long the grill lasts.
- When to retire it — how to tell a normal crack from a failed one.
- Clay konro grills — why none of this applies to them.
Why Cracks Appear
The grill below has been in use for about six years. The surface tells you as much about how it has been cooked on as any description could.
Minor cracks on the surface are entirely normal. They can appear within the first five uses, sometimes on the very first, as the diatomaceous earth expands and contracts with the heat. This is not misuse and it is not a defect — it is how the material behaves.
Underneath, the grill is held by a steel frame. That frame and the thick diatomaceous walls are what absorb the stress of thermal expansion, which is why surface cracking does not affect how the grill cooks.
What Diatomaceous Earth Is
Diatomaceous earth, listed as diatom mud on our website, is made of the fossilised remains of diatoms. It is naturally insulating, which is the whole reason konro grills are built from it: the walls hold heat in rather than letting it escape sideways or downwards.
That insulation is what lets a small charcoal bed hold a steady, high working temperature, and it is why a konro uses less charcoal than an open grill of the same size. The heat that stays inside the grill is heat that goes into the food.
Supply of the material has become a story of its own since the 2024 Noto earthquake — we have written about it in the Okunoto grill shortage.
Care
One habit matters more than everything else: store the grill indoors and dry. Diatomaceous earth is porous, so a grill left outside takes up moisture, and that trapped water expands the next time the grill is lit — which is what turns fine surface cracks into deep ones.
Beyond that, let the grill cool completely before moving or cleaning it, and never pour water into a hot grill to put out the charcoal.
When to Retire It
Surface cracks are cosmetic. A grill that has failed structurally shows something different:
- A crack running right through the wall, where you can see light or feel a draught through it.
- Sections of the wall moving independently, or a piece that shifts when pressed.
- The steel frame no longer holding the body tight.
- Charcoal or ash escaping anywhere other than the vents.
Any of those means the grill has finished its working life. Stop using it — a body that can no longer contain the charcoal is a fire risk, not a cosmetic problem. After years of service, that is the grill telling you it is done.
This Does Not Apply to Clay Konro Grills
Everything above is about diatomaceous earth grills — the Kinka Okunoto and Mikawa ranges.
Donabe-style konro grills are made of glazed clay, and cracks in the clay body are not normal. If the body of a clay grill cracks, stop using it and contact us. The only part of a donabe konro where crazing is expected is the diatomite trivet that sits under the pot.
- Konro grill user guide — setting up, lighting, cooking and shutting down.
- Japanese konro grills — the full range, diatomaceous earth and stainless steel.
About the Author
Written by our specialist Kai, with Melbourne chef Roger Young. For any questions, email hello@mycookware.com.au or use the chat box on this page.
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