Friday, August 7, 2009
Firing the Wood Kiln
My little kiln is made out of very used hard brick. They are AP Green Ozark and Empite bricks. They came from an old boiler that belonged to the Federal Government housing in Whitehorse. A friend of mine got a contract to tear it down and took the bricks for salvage. He had plans to build his own boiler, piled them in his yard and forgot about them for many years. He wanted to clean up all the accumulated 'stuff' so he had a big auction. Luckily for me I bought 1800 bricks for $200. Getting them back to my place 100 km away was a bit of a challenge. They weigh in at 8 lbs each. Got my neighbor's 3 ton Bobcat trailer and one of my 15 year old students and after three trips got them stcked on pallets at my place.
Thanks to Clayart on line pottery forum I found out about Steve Harrison's Laid Back Wood Firing. Bought it from The Potter's Shop and found the design of my dreams! Only took me a week to build. The first set of cone packs was from the front in the very first experimental firing. The pack was 8-9-10-11. All totally melted! Didn't side stoke so the back was between 6 and 8. For the next firing I plugged up some of the upper flues of the checkered flue. After I switched to the Hobs I started to side stoke and carried it through after every fill of the Bourry box. When cone 10 went down in the middle I called it quits. The most interesting thing about side stoking is how the flame in the kiln behaves when you put in a bundle of wood. It causes major turbalance. Instead of the flame flowing like a thivk river, it roars back towards the FRONT and goes in circles.
I have never used the damper while firing. I tried it, but it really causes it to slow down. I am firing by my self. I start at 4:30 am and seem to be finishing around 7 to 9 pm. Last time I didn't bother with a preheat and it went off faster. Go figure. Before I triend the side stoking it took until midnight to get done. Too long for me!
I can hardly wait for it to rain and the fire weather index to go down. I have some neat new pots to fire made from new and diffrent clay.
By the way. I top off my kiln with shelves, a layer of block insulation, a layer of soft brick and top it all off with fibre.