The first week of May, 1993, near the frontier town of Gulgong, NSW, Australia, on the Morning View property of potter, Janet Mansfield, an event took place which could be unique in the annals of ceramic history. Nearly 300 potters gathered together at this spot, about half a day’s drive inland from Sydney, for Fire-Up Gulgong. Billed as ‘A Practical Wood Firing Experience’, it was that and much more. To an outsider it must have looked like a cross between a refugee camp and Woodstock (Woodstoke?)—multi-coloured tents, wood fired showers, dunnies with a view, music, dancing, local wine and home made food, convivial campfires—it was as much about camaraderie and mateship as pottery.
But there was no shortage of pottery. Each participant brought upwards of 20 pieces, so there were thousands and thousands of pots. To five existing wood fired kilns, including an anagama and kiln for reduced lustre, glaze (Bourry box) and salt (trolley and Phoenix fast-fire), were added a giant pit kiln, a number of paper kilns, and the kiln which I built and fired twice during the event, The Gulgong Express.
The star of the event was the anagama kiln though, if for no other reason than its size and the effort involved in firing it. Although the technology originated in mainland Asia the term, ‘anagama’ is Japanese, meaning hole kiln, or cave kiln, denoting a single chamber, cross-draft, wood fired kiln, often built into the ground not unlike a small cave. Supplanted by other designs, the anagama was largely forgotten by the early 1600s; its use in modern Japan represents an anachronistic revival that began some time before WWII. While there are variations in size and shape, the most common configuration looks something like a beached whale half buried on a hill. It is an intrinsically inefficient design, requiring tremendous quantities of time and fuel to reach stoneware temperatures. This inefficiency, though, accounts for some remarkable effects. Though the anagama can also be used for firing work with applied glazes, it is most often used for unglazed work. Fired over a period of days (or in extreme cases, weeks), consuming mountains of wood, volatile alkalis and ash produced as by-products of combustion react with the clay being fired to produce naturally glazed surfaces.
My task was to demonstrate to participants of Fire Up Gulgong that it is possible to achieve long wood firing effects without the extravagant outlay of time, fuel and money that the anagama requires. Dubbed by the participants, The Gulgong Express, the kiln we built on the first day of the gathering is but one in a series of similar kilns called variously ‘coffin’ or ‘train’ kilns. In most cases these have been built on minimal budgets of materials scavenged or scrounged, and many of the design features have been suggested or forced by the quantity and character of materials available.
In this case, the entire kiln was made of a local white house brick, roughly equivalent to low grade dense fire brick. The kiln site was cleared and levelled, then covered with a five centimetre layer of builder’s sand. Ten centimetre hollow concrete block topped with three layers of brick formed the base. The main chamber is a rectangular box open at the top with internal dimensions measuring nine bricks (206 cm) long, three bricks (68 cm) wide and eight bricks (183 cm) deep. Both the fire box and the main chamber were roofed with kiln shelves covered with three to four layers of fibre blanket. (Previous versions have used soft brick over one layer of blanket, an arrangement I prefer.)
The firebox is a side stoked down draft (Bourry style) arrangement, three brick square and about 60 cm higher than the main chamber. Primary air enters over the wood, which burns from the bottom side as flames and (this is important) ash are pulled down into the setting. (In a more conventional Bourry box, because flames must go down, then up and over a bagwall, little ash makes it into the setting.) Hobs are positioned at roughly the same level as the top of the main chamber and the stoke hole positioned so as to facilitate stoking on to the full width of the hobs. The stoke hole was closed with a simple suspended door fashioned of mineral board and fibre blanket. At the base of the firebox, a throat arch, 45 cm off the floor of the kiln at the highest point, connects the firebox and the main chamber. The base of the fire box is stepped, inclined toward the floor of the kiln beneath the throat arch, which allows embers to fall toward the throat arch and the setting. Built into the steps are a series of air channels which enable the selective admission of secondary air into the embers.
A series of stoke holes, included in the front wall of the main chamber, allow side stoking, either directly on the pots or between pots, depending on how the kiln is stacked. These double as spy holes, though care is required when stoking in close proximity to cones and draw tiles. Steel angle was used at all the vertical corners, and the entire kiln tied together with fencing wire. Walls throughout the kiln are two bricks thick, with the exception of the chimney above the damper which is only one brick thick. Total height of the chimney was determined by my height, or rather by how high I could stack brick while standing on the kiln shed roof, approximately 3.3 metres above the top of the chamber. The back wall of the kiln and the base of the chimney share a common wall which is chequered to encourage flame to pass through the entire setting. The base of the chimney, which serves as a collection chamber, measures two bricks by three, corbelling down to two and a half by one and a half just above the main chamber of the kiln. A passive damper 23 cm square was built into the base of the stack. This is all the damper necessary during the firing; the active damper above the main chamber is necessary only at the end of the firing when clamming the kiln. Firing took a leisurely eight hours to cone nine, which temperature we held for approximately 24 hours. The greatest difficulty was in keeping the temperature down; the big fire box and the big chimney combination makes for a powerful engine. A combination of stoking into the main firebox and side stoking generated plenty of ash—if anything, too much at the front of the chamber, but there were a number of successful pieces and no small number of satisfied potters.
John Neely is a potter and teacher from Logan, Utah, USA.