Kiln Number One.
I had not seen a wood fired kiln, other than in photographs, before I built one. My friend, Peter Watson who got me started with potting, kindly lent me books and magazines. One book, "The Craft Of The Potter" by Michael Casson, had a plan in it for building a small wood fired kiln that could be used for raku or small earthenware pots. I bought some second hand fire bricks from a demolition yard, and made my first kiln, largely based on the plan in Michael Casson's book.
I had no idea if it would work, and was concerned that it might be too smoky, so I built it almost out of sight between the back of our house and the shed where it was screened from the main road and from neighbours. I fired it once to 1100 degrees Centigrade in little over 2 and a half hours. The clay that I put the cones in exploded and scattered bits of cone and clay over some of the pots and glaze test tiles that I put in, but I was really excited by the apparent ease of achieving a useful temperature and demolished the kiln so that I could use the bricks as part of something much bigger!
Kiln Number Two.
Kiln number two was a round up draft kiln. The chamber had a beautiful chequered floor that I gleaned from Michael Cardew's "Pioneer Pottery". Some other ideas were gathered from a book on making kilns by Ian Gregory. I also had ideas of my own, notably an attempt at a modified Bourry firebox. In its favour, the kiln did look very sculptural, and rather pretty in some lights, and there was opposition from Laura to the idea of pulling it down, but the fact of the matter was that the kiln didn't work!
Kiln Number Three.
(The photo above shows my friend and teacher, Peter Watson, and myself examining the results of a firing of kiln number three.)
I added a chimney to kiln number two where the firebox had been and converted it from an up draft to down draft kiln. I removed the top of the chamber and made a roof for it with an old kiln door. I made a new firebox on the same side as the kiln door. The firebox was of greater area than on the previous kiln, but was shorter and squarer. The firebox had to be partly demolished to enable the kiln to be loaded and unloaded, which was annoying. The firebox was also horribly low which meant that a day's stoking was really hard on the back and the knees. I did managed to nurse the kiln to around 1060 degrees Centigrade after a stoke of 8 or 9 hours, and fired some rather under done earthenware pots. I demolished all but the chimney of this kiln after one firing and designed something that would be easier to stoke.
Kiln Number Four.
Kiln Number Four was the first kiln that really worked. With the knowledge gained from the first three attempts I went back to the drawing board. I wanted a kiln that would be easy to stoke, and that would give a strong flame flashing effect on the pots. I put the firebox crosswise, and, dispensing with a bag wall, fed the flame in near the top of the chamber, and zigzagged it downwards to be collected at the bottom of the chamber below the lowest kiln shelf. On the way to the chimney was a second small chamber that had room for one or two pots. I used an old kiln door for the roof of the chamber, and recycled fire bricks for the main kiln construction with an outer layer of ordinary red house bricks for insulation. I had a really successful, and enjoyable firing of my first earthenware watering cans and some other smaller pots. The work was fired raw, and I found the firebox a pleasure to stoke, and the temperature rise easy to control.
The top of the chamber fired hotter than the bottom, this was as I predicted. More importantly, the top of the chamber had really good flame flashing, and the pots that were on the top shelf toasted up beautifully.
It was with real sadness that I later demolished this kiln and made way for kiln number five, as kiln four had real potential. The main problem was the small chamber. Also, the strong flame flashing suited unglazed work, but would have been a problem for glazed pots.
Kiln Number Five.
Kiln Number Five, a round up draft kiln, does work quite well. The firings take about 5 to 6 hours to get to 1200 degrees centigrade in the lower part of the chamber. The kiln is quick to cool down, and can be unloaded the day after firing it. The kiln has three levels of triangular kiln shelves that are arranged around a central prop like segments of an orange. Little gaps in between the shelves allow for the heat and flame from the firebox to rise through the chamber. The lowest part of the chamber is much hotter than the top, but I can rely on about 1200 degrees on the bottom shelf, around 1150 on the middle, and about 1060 on the top shelf. Glazed pots can turn out well in this kiln, and pots can also get strong flame flashing on the lower shelf. It is possible to fire too quickly with this kiln (in excess of 400 degrees centigrade per hour gain), or to loose heat fast if not fired with care. Above 800 degrees centigrade, the kiln is also likely to go into strong reduction if too much wood is put on at a time.
I still have this kiln, but have made kiln number six, an even firing down draft design, to get to stoneware temperatures.
Kiln Number Six.
Kiln Number Six is my production kiln. I mostly fire it to cone 11 to 12 in about 12 to 13 hours, although it could get there much quicker. The kiln was built mostly with new fire bricks. There is a layer of hard brick within the chamber that is backed up with K23 insulating fire brick. K26 insulating bricks form the arch. The kiln was inspired by a much smaller gable arched wood kiln designed by Jim Schuld that I saw in a Ceramics Monthly magazine. My kiln differed quite a bit from his design, but I liked his fresh ideas and his use of unusual materials, and the article was a great help in getting me started. I will write an article about my kiln, with some diagrams, so won't go on at length here.
Kiln Number Seven.
(Top photo shows my friend, Dave Sharp, casting his expert eye over one of the raku pots. Dave is an enthusiastic raku potter.)
Kiln Number Seven, is a small raku kiln. It is capable of reaching 1000 degrees centigrade in about two and a half to three hours. Whilst taking out a load of pots the temperature in the chamber drops to about 600 degrees, but is back up to 1000 degrees in 20 to 25 minutes. I use a cross draft firebox, and, because of its short length, the front part of the chamber is fairly oxidizing and the back part tends towards reduction.