Firing the First Wood Fired Kiln

Our first experience in firing a wood kiln was at Mitraniketan’s pottery unit. It’s something we really wanted to do and hopefully do much more of because we intend to eventually build a kiln of our own and wood fire our own things.

The kiln happens to be huge: with a chamber that can fit up to 400 of the compost pots and possessing not one but two fire boxes. We aptly named her Mama Beast. We were in for a treat.

Mama Beast is a downward draft kiln, meaning the air cycles through the chamber inside. The heat rises from the two fireboxes, moves down through the chamber and gets sucked into the chimney opening which is located at the bottom rear end. The advantage in this type of kiln is a higher fuel efficiency due to the circulation: heat is retained in the kiln for a longer period before escaping through the chimney. However, because the two fireboxes are separated from the chamber by a wall (in this case with holes), it requires considerable time before the separation walls themselves are hot enough. Kiln advantages and disadvantages are circumstantial: what one considers a disadvantage, another considers an advantage!

The kiln had been painstakingly loaded the day before and its chamber opening sealed with bricks and a wet mixture of sandy mud. There were roughly 400 pots stacked inside. At 8 am we commenced the firing with a little kiln spirits ceremony of lighting incense sticks and placing a banana leaf with a little sweet at the chamber opening. Then began the 3-hour “smoking” of the kiln, a slow warm up, for which coconut husks (true Kerala style) were used to ignite the fire. Only a few logs are kept burning at the front end of the fireboxes. While the kiln was smoking, we began to stack the wood which would be needed throughout the day, roughly 1.5t, from the store house.

In India wood is a cheaper commodity than gas or electricity so many traditional potters choose to wood fire. Gas is more commonly used by studio potters in the cities. Electricity is as unreliable with its frequent power cuts as it as it is expensive. Divya from Talking Clay Studio runs a skutt kiln and must frequently restart her firing and accept the damages of a power cut in the middle of her firing cycle.

During the 4-hour “slow firing” phase the fire is contained in the front half of the fireboxes. The logs are tossed in half way and the mouths of the fireboxes remain open, so this was the appropriate time to learn how to throw the wood into the tunnel. We observed him diligently as he tossed the logs in with careful measure. You should aim and use just enough force to ensure that the log lands in the middle segment of the tunnel without hitting the walls: we practiced this art of log tossing for a while.

Finally, the kiln is pushed into a 5-hour phase of “full firing”. We made ourselves comfortable with snacks and chairs on the green. We no longer had the time to wander too far from the kiln. Every 40 minutes the fireboxes were fed with wood: the entire length of the tunnel is filled with wood. Every now and then Anil checked the state of the pots and chamber through the peepholes in the front. The last peephole is the bottom one: when the pots down there began glowing a nice red the heat had spread throughout the whole chamber and we were almost done with firing. It was roughly 900°C in there. No more wood was needed. We waited till the remaining wood had burnt to then stir the coal with a long pole. Then the fireboxes were shut with metal plates and bricks were placed in front of the ash pits.

The red glow of the kiln looked beautiful against the night and we felt satisfied having worked around the kiln for the whole day.

Two days after the firing the sealed kiln door was opened. The pots were still too hot to touch and a few more days were needed before unloading could begin. The pots looked great and we could see a slight colour difference from top to bottom caused by temperature difference. Five days later the kiln was cool enough to unload. It took a little time to unload 400 some pots. Anil made sure to check the sound of each pot to hear for a crack. It’s interesting to observe that the pots on top are lighter in colour and have a higher sound than those on the bottom that are also darker in colour. It was a hugely successful firing: from the 400 or so pots, only 6 were damaged. Everyone was pleased. Wood firing isn’t a dull job; it’s labour intensive team work. And we like it already. This was a rich learning experience.

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