DETAIL OF AN INSTALLATION / Coal, iron, stoneware / Lunds Konsthall / Lund, Sweden / 2000
THE ARTIST FEEDING THE KILN WITH COAL / Each burning process lasts about 24 hours
THE ARTIST LOOKS THROUGH THE FLAME / To identify the correct temperature during firing
BURNING PROCESS
GLAZE / DETAIL
GLAZE / DETAIL
PLATE / Stoneware / 60 cm / Collection National museum / Stockholm, Sweden /1974
PLATE / Stoneware / 60 cm / Collection National museum / Stockholm, Sweden /1974
SPHERE / Stoneware /110 cm /1996
LARS FREDRIK PETTER ÖSTBERG / Gustav Kraitz / Bronze / 1960
IN OPEN FLAMES
GUSTAV KRAITZ’S
ACCOUNT
OF CERAMIC TECHNIQUES
by Jon JohanssonWe - a painter and a sculptor - were searching for the perfect material for our joint creative work. We chose ceramics. Ceramics with a Chinese glaze. We made our decision when we saw a small medallion with fish in Nils Palmgren’s book, Sung Sherds. They were glazed with a thick, lovely celadon glaze. The sculpture and glaze interacted in a way that was completely new to us. It was 1963. People often ask why we fire in this primitive way when there are modern technological options (gas, oil or electric kilns). The answer is simple. No technology can match the beauty of glaze produced by a large flame kiln. We have tried all types of kilns over the past thirty years and have chosen probably the most difficult yet the most rewarding method. The kiln has a net space of approximately eight cubic metres. But that does not mean that all firing cycles yield the same amount of finished material.
We accept about 20 percent, and the rest we re-fire two, three and four times. A work can be improved, but it can also be completely destroyed. We increase the de- grees of difficulty with the reburnings.
A stone object sintered at 130 C°, which can weigh up to 100 kg, is subjected to such high stresses that it will crack or, in the worst case, be destroyed. Working with ceramic sculpture requires you to develop a system that should never be abandoned. Firing large-scale sculpture is very different from firing turned objects that have their own laws. If you follow those laws, you will get an almost 100 percent result after a period of practice. But burning sculpture is a constant, tension-fueled adventure.
As long as you can analyse the errors that occur again and again, you can move on. The possibilities are endless. We fire with wood and coal. The first step is to prepare the kiln for firing. The sculptures must be placed in a kiln that has reached the correct temperature, which is between 60 and 80 C°. (The Chinese used a small fire in the oven to keep it dry). We use liquified petroleum gas to preheat. Once the kiln is packed and bricked up, it is heated to175C° for two days. The whole oven must then be thoroughly heated - including the draught system.
Then we fire it with wood. This stage of the firing is equally difficult every time. Through three firing holes, it is easy to get the temperature up to 500 C°, it can be done in half an hour. However, if the temperature rises by more than 70-80 C° per hour, larger objects will crack.
At around 700 C°, you switch to coal, where the calorific value should be 5-7800 and the slag melting point is below 1280 C°. Why fire with coal and not wood in this phase? Using wood is an option, but it would require an enormous amount of labour and is not suitable for two people like us. The emissions of harmful substances will be minimal anyway, as almost everything is burnt within the furnace chamber at the high temperatures involved. To give some examples of how we attain our colours: a dark cobalt blue glaze is never finished with one firing. It must be fired at least three times. Or the Song-type celadon glazes achieved by using feldspar that becomes matt at lower temperatures but acquires a glassy surface at higher temperatures. They are completely free of colour additives and dyes. When re-fired in a reducing furnace atmosphere, they take on a light green colour from the iron naturally present in the clay.
We use different types of wood for burning. Dry apple or pear wood will give you the best results. The fly ash entering the kiln with the flames is the most effective way of producing the beautiful green celadon glazes. Firing with alder wood will result in all the objects in the kiln turning a buttery yellow. We quickly learned just how much the type of wood used affects the colour of the finished object when we used surface wood from the slipper factory in Troentorp to fire with. The wood gave all the goods a yellow colour. The colour variations depend on how much you stir the hearth during firing. You can also cover objects so that only some of the surfaces are exposed to the ash.
You must test and develop your glazes yourself. A single basic glaze can create a multitude of variations when it is fired with different fuel types. The glazes that work in my kiln will not necessarily work in another. Each kiln is like an individual who requires special treatment. Given the wealth of research on Chinese ceramics, it is surprising that there are no useful technical descriptions on manufacturing methods and kilns.
The only thing available are picture books based on original Chinese paintings, but the authors have not provided much information beyond what the reader can already guess.
Let me give you an example of just how exciting an adventure this artform is. In the mid 1970s, I placed a large dish at the bottom of my kiln. It was a built-in system, and I had to leave it in for four firings. But when I finally removed it, I discovered a shimmering green celadon dish, in a hue I had never seen before. It was a masterpiece of the finest Chinese Song. I must admit that it was a happy accident. I attempted to repeat the process and put in four objects of the same type with the same glaze. I fired them once, twice, three times and came close to achieving what I was looking for.
Then, I put them in for the fourth firing. I was extremely excited to see if I had succeeded. The kiln was opened. All four items were destroyed. The firing had taken place in foggy weather and I had not preheated the kiln. There was just no circulation and all the smoke settled on my already fine green dishes.
Everything turned brown. After that, I did not attempt the same experiment for many years. I burned hundreds of times, but only succeeded with that process again in 1992. Happiness can be experienced in many ways. To me, nothing compares to the happiness you get from burning in the spring when the beech forest bursts forth. After a long burn, you get tired. But then, at three in the morning, when the blackbirds start their morning song in the clear air and nature suddenly wakes up, I sit in the old armchair by the stove that breathes heavily and rhythmically and listen to the birds’ fantastic concert. Slowly, the beech forest, which has suddenly begun to turn green, starts to brighten. Spring has arrived. I finish the burning. The whole thing is like a liturgical event. I know the burning has gone well but I will only see the results in a week. I experience a feeling of joy that few people are privileged to feel. Working in this way makes you experience the creative process in its entirety.
This, for me, is art.