What happens when we open the kiln

Two days of firing, a day of cooling, and ten minutes at the door finding out what worked.

A firing takes about thirty-six hours from the moment we light the burners. For the first twelve the kiln climbs slowly, driving the last water out of the clay. Then it climbs fast, and at around 1,000°C we close the dampers and starve the flame of air, which is what turns iron glazes green and blue instead of brown.

The top of the firing

We watch small cones of clay, called witness cones, through a spy hole in the door. Each one is made to bend at a known temperature. When cone 10 has bent over and touched the shelf, the kiln is at about 1,280°C and we turn it off.

Cooling

Then nothing happens for a day. The kiln cools on its own, and opening it early cracks pots. The hardest part of the job is not opening the door.

The door

When we do open it, it’s still warm. We take everything out shelf by shelf and the pieces that made it go straight to the shop the next morning, after the people on the email list have had a look.