Feature Article on Dunbar Pottery & Anagama Kiln
Main Article: 1209 Words
Philip Revell is a man of multiple talents. As a research student of engineering (a profession that he went on to work in for a number of years ) at Warwick University in the ‘80s, he met David Jones. Jones, who now lectures at Wolverhampton University and is author a number of works on raku and firing techniques, had set up a pottery studio on a farm on the edge of the Warwick campus. It was here that Revell got his first taste of potting: “I found working with my hands and with clay to be an intensely therapeutic antidote to academic research and became hooked,” he says.
Philip came to engineering through an interest in the ‘Small is Beautiful’ philosophy as espoused by E.F. Schumacher. After returning from working with peasant farmers in Zimbabwe, Philip worked at the Centre for Alternative Technology in mid-Wales. It was here that he set up his first pottery workshop.
Since 1990 Philip has operated his pottery from the basement of an elegant Georgian townhouse in Dunbar, near Edinburgh. The flagstone floor, range, pantries and other original fittings somehow seem an appropriate place for such a venture. The sprays of elemental clay, the kick-wheels and kiln, chime with the simplicity, harmony and solidity of the surroundings.
Near the beginning of the new millennium, Philip began organising a number of projects at Pishwanton Wood , an experimental bio-dynamic land management centre based on Goethean principles - that nature is a seamless whole, that our inner life is part of the outer world - in the Lammermuir Hills. These included the building of a wood-fired, two-chamber, noborigama stepclimbing kiln, so-called because they are traditionally built on slopes with each chamber higher than the one before. After leaving Pishwanton to set up the environmental organisation Sustaining Dunbar, Philip began to develop the idea of building a kiln nearer to his pottery. Eventually he found a site at the wonderfully-named Phantassie, an organic farm, ideally placed only a few miles away - and with a ready supply of firewood from the farm.
Philip used the recycled materials from his Pishwanton kiln to construct a simpler anagama kiln. The term comes from the Japanese “穴窯” meaning ‘cave kiln’ and probably alludes to how the first types of the structure were created. In this instance, because of the vagaries of the Scottish climate, Philip began by building a simple, open wooden shelter under which the anagama kiln was assembled. Starting with cement slabs on a hard-core base, Philip used high alumina firebrick, HTI (insulating brick) and a mixture of locally dug clay, sand and sawdust for insulation to complete the elongated, curving structure.
Philip’s kiln, which he built in his spare time in the evenings and at weekends, took about a year to complete. It was built to his own design with a firebox in the front, and extra stoke holes along its 3-metre length, which allow for the creation of additional fly-ash. Inspiration for the design came from photographs and drawings of other kilns, especially those of potters John Butler, Svend Bayer and the late Patrick Sargent. Philip explains, “I was getting a little bored …. and was keen to build a new kiln with the potential for more 'extreme' wood-fire effects on the fired pots, i.e. a design that encouraged more ash to fly through the kiln during firing.”
To date the kiln has yielded some impressive results. Philip’s pots have clean lines and a no-nonsense, functional aesthetic. His mugs often curve inward from the base and then outward towards the rim. The handles are broad and roomy, allowing the thumb to rest comfortably and afford easy tipping while drinking. These are complemented by capacious, but elegant teapots, which are balanced and pour well with the aid of handles that have space for three fingers while allowing the thumb to sit on top. Philip’s plates have a similar, well-made solidity with broad bases and a shallow lip. He also makes jugs, bowls, pitchers and larger garden pottery, such as plant-holders.
“As a largely self-taught potter, I find the attempt to master the many facets of this exacting and technical craft to be an ongoing challenge, which is what keeps me at it. Apart from the physical challenge of throwing and manipulating clay, there is also the need to develop an appreciation of form, to understand the raw materials that can make up a clay body or create a glaze, to experience how these materials interact and are transformed by fire,” he comments.
The process of loading the kiln is, in itself, a time-consuming and skillful business. Space is at premium and care must be taken to allow the flames to seek out all areas of the kiln, unimpeded. Philip uses a series of spyholes through which he can check on a series of cones which indicate appropriate temperatures. The optimum firing temperature for the kiln, stoked with softwood, is around 1340°c. The entire process of loading, firing, cooling and unloading takes several days and the potter must be present for much of this.
Philip fires his kiln based on the reduction principle. This means that the oxygen supply is restricted, by blocking up the intakes with bricks resulting in a saturation of ‘free carbons’ in the atmosphere, mostly in the form of carbon monoxide and carbon dioxide. Because the fire needs oxygen to burn, the flames seek oxygen within the clay and glaze. Reduction firing can bring out some wonderful colours - ‘shino’ and ‘copper red’ are typical of high-fire glazes.
The fire-box is situated at the front end of the kiln with the chimney at the far end. The forced draught from the chimney creates a current, of hot gases which move between the pots, carrying a quantity of fly ash from the wood-fire with them. It is the current of burning gases and fly ash, heated to full temperature and settling on the pots, which forms the patterning on the pottery.
Philip uses glazes on the areas that are least likely to be affected by fly-ash and ‘flashing’ or flare-ups. He uses ‘celadon’ and ‘nuka’ wood-ash glazes - the former comprises wood-ash, felspar and clay in a 4:2:1 ratio. The 'nuka' mimics a straw-ash glaze by adding quartz to a wood-ash/felspar glaze, with clay, in a 3:3:3:1 ratio. The ‘nuka’ gives a glossy white glaze - with a tinge of blue where it works well. Philip also uses a simple 'shino' glaze, made up of ten parts nepheline syenite to four parts clay.
Perhaps the most nerve-wracking part of any potter’s business is the process of opening and unloading the kiln. With Philip’s anagama kiln, the anticipation is augmented by the experimental nature of the undertaking. As the bricks are removed to reveal the firebox, the first pieces are removed, still very hot and with the use of gloves. On one of the first pots removed from the front of the kiln there is clearly a line of blue-ish glaze along the rim of the bowl. On the left area there are clear signs of 'burning' caused by the current of flame, smoke and gases - one of the effects of reduction. The bowl is therefore a witness not only to the potter’s hand and eye, but also to the complex chemistry and physics within the kiln itself. Flames and gases have created patterning and tonality, dictated by their passage around the contours of the vessel. An ancient technology is still able to provide unpredictable, beautiful and unexpected results while still keeping some of its secrets intact.
Firing schedule for the Phantassie Anagama Kiln:
· pre-heat, 10 hours or so, to get the front of the kiln up to about 300 °c and ensure everything thoroughly dry.
· gently raise the temperature to about 900°c at the front over the next 12 hours, then start side-stoking to raise the temperature at the back of the kiln
· gradually raise the temperature to about 1000°c over the next 3 to 4 hours
· start stoking more frequently and restrict the air inlets as necessary to ensure heavy reduction as the temperature is gradually raised to 1340°c over the next 12 hours, side-stoking at intervals to bring the back of the kiln up to temperature (in practice the kiln will move in and out of reduction continuously each time wood is stoked and the pyrometer readings are not a particularly accurate indication of actual temperature)
· continue stoking and side-stoking to maintain the kiln at this temperature for 14 hours or so, maintaining a light reduction for as much of the time as possible and aiming for cone 11 to be completely over at all five spy holes - top, bottom, front and back.
· start reduction cooling - close the chimney damper and air inlets completely and occasionally stoke with very green wood and spray water into the firebox as necessary to maintain reduction as the kiln cools to about 1050°c. This takes about four hours. (The water reacts with the charcoal in the firebox in the water gas reaction to create carbon monoxide and hydrogen, creating a strongly reducing atmosphere).
· open the chimney damper slightly and crash cool in oxidation to about 900°c
· close damper and all air inlets and leave to cool naturally