Back in 1998 a meeting was held by members of the Auckland Studio Potters who were interested in wood-firing. The purpose was to build a wood kiln and, realising that the ASP didn't have the resources for the project, we decided to put up the money ourselves to buy the bricks and other stuff necessary for the kiln. We built the kiln at the ASP as we wanted to encourage other members and students to get involved. So an account was started, bricks purchased, location found and construction started.
The design of the kiln came down to two options, a Bourry box style kiln, or a relative of the Olsen Fast Fire called a Phoenix Kiln. We decided on the Phoenix as it seemed a useful looking kiln (and by this time I had already built and fired a few times a bourry box style kiln at UNITEC, and I wanted to try a different style of kiln as well).
The basic plan was for a large firebox directly underneath the kiln and a chamber size of around 30 cuft - large enough for the 18 or so members to put work into for the group firings, but not too large that we'd never fill it. The grate was originally metal fire-bars but we ended up going through a number of various grate options as we learnt how to fire the kiln. The most successful version was a Dutch oven style grate made of brick which is slightly higher than halfway up the firebox. This solved most of the problems of ember build up and choking the firebox and has lasted very well.
Other tweaking we did with the kiln after the first firing was to build the chimney higher by about 3 feet as it was obvious we didn't have enough suck for that size of firebox. We also tried different door systems in-front of the firebox opening - it is a hot kiln to fire and a series of hinged flaps or iron shields were experimented with before realising that the most successful firings were ones that just left the firebox open and piled in the wood. It does make for an exhausting last 6 hours of firing - but as most of the firings now take only 12 hours or less, it's not too bad (unless you fire in shorts and jandals!).
The wood we've used over the years has changed, starting off with broken up pallet timber, delivered by container truck. This worked well, but filled the car park with nails, then a source of mill slab was found, and that was excellent to use. But problems of seasoning the wood and storage made the odd firing a disaster. Now the mill slab has stopped it's pallet timber again.
Apart from the fun and games with the grate and the firebox doors the only repair work done on the kiln is to re-build the throat of the kiln. This was necessary as the part of the firebox arch nearest the throat was slowly creeping into the gap, which slowly lengthened each firing. Early in 2005 we smashed out that part of the arch and chamber floor, made up a wooden former and recast that section, including more bracing to stop it happening again. So now after 11 years and numerous firings the Phoenix kiln is going strong.
Currently I use Phoenix kiln that was built by the members of the Waikato Society of Potters in their central city studios. It is a beautiful kiln to fire and reaches temperature in about 9 hours with pallet timber. We have to be very careful of the smoke produced as we're 2 blocks from down town Hamilton. It has a taller firebox than the ASP kiln and we have much of it bricked up during the firing, making it considerably more pleasant to fire - it is also a little taller. When adding soda to the kiln I now only spray in two places in the kiln once cone 6 has dropped and use about 1.5kg of soda ash. So it is a little soda and reactive slips that work for me now. |
