Why tenmoku is fired twice

The first firing, around 800 °C, turns clay into a body that can take wet glaze without dissolving. The second, at 1,300 °C in a reduction atmosphere, melts the iron glaze and lets it run.

Skip the first firing and the glaze crawls; fire the second too fast and the crystals never form. A tenmoku cup that looks calm has usually been through a slow climb and a slower cooling.

We fire in a gas kiln in Jianyang. Each firing takes three days: two to climb, one to cool.