Some time ago I promised my little group of students a session with my Raku kiln. Unfortunately the weather did its best to rain on the days that we arranged to fire the kiln, so things were put off for a while. On Monday, things were fine here, so I did a test firing of the kiln in the afternoon, and one of my group came to watch the latter part of the proceedings. On Tuesday afternoon we were able to muster two of the three students, and so we fired some work. Toasted marshmallows were a feature of the afternoon, and the two cooks had their own thoughts as to what made a perfect toasted marshmallow. One preferred charred to perfection, and probably on fire, whilst the other took a more subtle approach, going for a light brown crust concealing a soggy interior.
Fire drill was practiced after the firing. Well, the stirrup pump did need to be emptied!
Today, Thursday, I did a firing of my own work. I was impressed with the results of the firings on Monday and Tuesday, and have to send some new work to a gallery tomorrow, so... I thought the Raku kiln might add a bit of magic.
Light to moderate rain actually proved pleasant to work in, and gave atmosphere to some of the photography. Laura took most of the photos of the event.
Very occasionally I managed a brief sit down, but firing a Raku kiln is demanding, and most of the time I was feeding wood into the firebox, and watching the temperature go up, drop, then climb again. Every new piece of wood gave a noticeable dip in temperature, before climbing away.
Our alarm clock kept a watching eye over events. I find it very helpful to mark the temperature on graph paper every quarter of an hour, to measure progress. This kiln will get to just over 1000 degrees Centigrade in just under two hours. I fired to 1050 C for this firing.
I fired quite a lot of the time in reduction, that is a somewhat oxygen starved state. I hoped to add carbon to the unglazed clay, and to turn copper greens red. The flame coming out of the spy hole shows a reduction atmosphere. That poor flame is hungry for oxygen and will get what it can outside the kiln if it can't find enough to satisfy it inside.
At the start of the firing I build up a fire in the ash pit. As temperature builds I establish a fire on the grate.
At 1050 degrees Centigrade I open the chamber door. You can see the bright river of fire rushing from left to right. There appear to be several phoenix birds in the kiln!
I take out each object from the kiln.
Each pot is placed on a square of newspaper, and a tin with some shredded newspaper in it is placed over the top. After about 30 seconds the tin is slightly lifted to admit some air. The paper immediately ignites, and, when it is burning fiercely, the tin is pushed down firmly to cut off the air. The flame uses up all the air in the tin and the fire goes out. Meanwhile back at the kiln, a new load of pots that has been warming over the firebox is put into the still very hot kiln chamber. The door is shut, the kiln stoked, and the kiln quickly bounces back to 1050 degrees C.
When the pots have cooled down a lot, I remove the cans and I put the pots in a bucket of water, one at a time. You have to be careful with bottles, if they are very hot, water flowing into them can flash immediately into steam and eject boiling water with great force. Once the cans are free, they can be primed with shredded newspaper and be ready to cover the next load of pots from the kiln.
After the pots have cooled, they can be gently cleaned with a wire pad and Brasso, or some other brass cleaner.
In some cases, the oxygen starved atmosphere in the tin managed to turn the copper in the glaze, into a thin layer of copper metal. Where the reduction atmosphere was less severe, various shades of copper red were produced. Where there was plenty of oxygen, the glaze was green.
You can see from the varied colours how different parts of these birds received greater or lesser amounts of oxygen.
The underside of these little bowls shows the carbon impregnated unglazed clay around the foot of the bowl, and the shades of green, red, and copper are visible.
A new bird was seen in our garden today!
Here are most of the bowls and birds that came out of the firing.
Ginger found all this hard work quite exhausting, and rightly chose to go to bed!
*The word Raku is a Japanese word meaning pleasure or enjoyment.
**Raku -according to Wikipedia