|Titanium white pot fired in reduction.|
|This was a copper green pot, now copper red through the oil drip reduction firing.|
It is all about atmosphere! Sunshine, wind, fog, darkness, make us feel different moods, from bliss to terror! In the kiln, atmosphere can dramatically change the appearance of a pot. Give it oxygen, and the colours will probably be brighter and clearer. Starve the kiln of oxygen, and introduce some carbon monoxide, and the pots will have an entirely different mood and may turn dramatically different colours!
|The two front pots were pale green and ivory white before reduction firing, and the two at the back share the same glaze. The white one is oxidized, and other is fired in a reduced atmosphere!|
In a wood fired kiln or gas kiln, it is possible to control the atmosphere whilst firing. Just adding a little more fuel than can be easily burnt will deplete the kiln of oxygen. An electric kiln normally doesn't offer that choice. You switch the thing on, the elements glow, and the kiln atmosphere will be mostly neutral to oxidizing, depending what you have in it. Of course some of us like to experiment. Potters have done all sorts of things, including firing gas or oil burners into electric kilns, or dropping in moth balls, sugar cubes, or thin sticks of wood. In a regular electric kiln this can be hazardous, hard on the kiln elements, and not always reliable.
|Rutile glaze, first an ivory white in oxidation, now soft green and purple in reduction.|
I have been playing with re-firing crystalline glazed pots in reduction atmospheres (reduction refers to reduced oxygen). My first experiments were with a small wood fired kiln that I made for the job. Some of the pots from these firings were lovely, others were not, but it was an interesting and exciting way of working. See my post "Crystals in the smoke!" for some photos of wood fired crystalline pots. A few days ago I did my first cooking oil drip reduction firing in an electric kiln with some crystalline glazed pots, and the results were very successful.
|What happens when an artist's easel, a lawnmower petrol tank, a short length of tubing and a kiln get together in a confined space!|
|Oil drip reduction fired copper glazed pot from the top.|
The firing was quite simple, just a question of taking the kiln up to about 800 Celsius (1472 Fahrenheit) , switching it off, then adjusting my cooking oil drip apparatus to give approximately one drip of oil per second through the tube into the kiln, and keeping that going until the kiln had cooled to about 600 Celsius (1112 F).
|Copper glazed pot. The mild looking reduction was sufficient to turn this not just red, but also quite metallic looking.|
I did undertake the exercise with considerable care as I have only read about this procedure and have not seen it done. I changed out of the polyester jacket I was wearing and put on cotton overalls, and I kept not one, but two small fire extinguishers within easy reach just outside the shed door. Some of you will know from cooking, just how dramatic a cooking oil fire can be, and I wanted to be able to make sure that it was possible to keep one under control if something went horribly wrong.
|I was tempted to give this a reduction firing, but like it too much as it is. This pot reminds me of the recent snow that we have had here.|
As a wood firer, I was intrigued to see just how little visible smoke was seeping from the top bung of the kiln, and I did wonder if the oil drip would be sufficient, but I am happy to say that the results were dramatic!
|Here is a close up of the pot with the rutile glaze fired in reduction.|
In the first firing I kept up the oil drip for three hours. In the firing that I am doing as I write this, the drop in temperature is much faster, and I will be shutting off the oil drip after two hours. It will be interesting to see if there is any noticeable difference in the way the pots look.