High-fire refers to a range of temperatures between cone 8 and 13, but is collectively referred to as “cone 10.” Stoneware vitrifies nicely at these temperatures making it an excellent choice for functional work, but be aware that it takes considerably more (usually fossil) fuel to reach these higher temperatures, therefore increasing the economic and environmental cost of the firing. On the flip side, many beautiful high-fire glazes can be made from the most economical of ceramic ingredients, which defrays some of that additional cost. Also, if you are interested in wood or salt firing, high fire is the place to look. Although you can fire a salt or wood kiln to a lower cone, these are most often fired to cone 9 or above. Salt and wood firing offer a unique aesthetic and culture for the clay artist to explore.

TYPES OF REDUCTION

A kiln that uses combustion to heat can create a variety of different atmospheres. A live flame requires oxygen to continue to combust. If plenty of oxygen is flowing into the kiln, an oxidizing atmosphere can be maintained, similar to that in an electric kiln. However, if the damper of the kiln is pushed in to reduce air intake, you get incomplete burning and the result is carbon monoxide rather than carbon dioxide. This is called a reduction atmosphere. Carbon monoxide wants to become the more stable carbon dioxide and finds oxygen molecules wherever possible. Coloring oxides such as iron oxide or copper oxide readily give up oxygen and in doing so change states giving different color responses. The same copper oxide glaze that gave you blue-green in oxidation can give you sang de boeuf red in reduction. To control the volatile process, some potters will use an oxyprobe to assess the atmosphere inside the kiln. Because these cost around $1,000 (€730), many potters instead rely on visual cues, trial and error, and maintaining detailed kiln logs to gain control.

For most of our students, a “light” reduction is equivalent to a complete failure on the part of the kiln tech, as copper reds look salmon colored, Shinos are less dynamic, and the color of the clay body is too light (see image at right). Sometimes you’ll hear, “Oh, it was a bad firing. Completely under-reduced,” accompanied by a groan of disgust. There is often great pressure on kiln techs to fire work beautifully for everyone, so please be kind in the case of a less than desirable firing unless you are willing to learn the ropes and take on this responsibility yourself!

As with the previous chapter, for each glaze, I dipped each of the tiles for a two-second count in the same glaze. I then inverted the piece and dipped the top one-quarter of the tile in a different glaze.

For the three or more glaze combination tests, I dipped the entire tile in the first glaze for two seconds and let it dry. I then inverted the piece and dipped it into a second glaze for one second. The pieces were then given several hours to dry under a fan, at which point a third glaze was applied by inverting the pieces and glazing the top one-quarter of the tile for one second. Finally, for certain combinations, a fourth glaze was applied at the very lip of the pot by inverting the piece and dipping it in glaze for one second.

Though high-fire gas kilns, salt kilns, and wood-fire kilns are less common than their electric counterparts, these types of kilns create community around them. Often larger in size, ranging from 8 to as much as 300 cubic feet (0.2 to 8.5 m³) or more, these kilns can require long hours—and in some cases, teams of people working in groups—to manage a firing. An overnight shift on a wood kiln is a bonding experience, and many friendships have been forged through the common goal of bringing a fire-breathing dragon to life in order to vitrify clay and melt glaze. Firing these kilns can be demanding. It is hot, exhausting, and requires constant mindfulness of the flame and the body’s relationship to it. Here, the term “high on fire” comes to mind. For the fire potter, this is where she feels most alive.

The Odyssey Salt Kiln is one such kiln. The Old Salt Kiln, designed by a former Odyssey resident, stood for nearly a decade and saw more than 135 firings. Slowly the buildup of salt and soda on the interior walls of the kiln created a tension that caused the arch of the kiln to begin to sag, and for safety reasons it had to be dismantled. This is the natural life of a salt kiln, eventually falling in on itself. As a beloved but temperamental kiln, the bricks from the Old Salt Kiln now create the wall of our studio flower and herb garden (see photo above).

We began plans to rebuild immediately. We commissioned a new kiln design from master kiln builder Shane Mickey, who also advised us on the project. Over the course of the spring of 2019, we first raised the funds to buy the raw materials, including new burners. Then, on a series of successive Sundays, a volunteer crew of eight potters and resident artists poured the concrete slab, bricked the chimney and walls, installed new irons, and rebuilt a beautiful new arch. Building a kiln is an empowering experience and an excellent opportunity if you get the chance. You’ll get a deeper insight into the physics of firing, not to mention the connective human experience of building an arch. The first time you do it you feel as if your brain has expanded, as you participate in part of the evolution of our species and culture.

The kiln can take as few as several hours to load, or as much as three days in the case of the largest kilns! The door must be bricked up every time, and the firing involves the spraying of a soda ash solution directly into the hot kiln. Salt (and soda) firing is a dynamic process that must be treated with an eye on safety. You are working with a live flame, adding materials to that kiln that are both vaporizing and corrosive. The result from all this work, however, is an effect that cannot be achieved otherwise: that gorgeous orange peel texture on the raw clay (see photo at right). I have also always loved salt kiln glazed work, when the vaporized salt or soda has landed on the molten glaze in an atmospheric chemical interaction that changes the look of the glaze by giving it more depth.

Similarly, wood-fired pots have a certain mystical quality to them, having spent days in the path of an active flame, with wood ash traveling though the atmosphere of the kiln and landing on the surface of the pots to color them. Wood ash contains a high percentage of calcium oxide and also potassium oxide and trace elements of iron, manganese, zinc and copper oxides, all capable of affecting color and flux on the surface of your work. Pots placed unglazed in the wood kiln emerge colored like tobacco, bourbon, leather, or stone. It is as if these pieces had been excavated from an ancient archaeological site (see photo shown here).

Wood firing connects us with the history of ceramics, and where we came from as potters. Just as electric kilns and their computerized technology inform the final product, so too does salt and wood fire in their own unique ways. I hope you will have a chance to try all of these different firing methods in your travels. Though you may decide that you prefer one style of firing over another, this experimentation will help you orient yourself within the field.

Gillan Doty Grabs the Dragon by the Tail

>Articulate, intellectual, and physically inexhaustible, Gillan Doty and his strongly thrown wood-fired vessels burst onto the Asheville ceramics scene in late 2017. Although you’ll often see him studying the history of ancient kilns, you’ll also find Gillan jogging up the steep hills outside of town. Gillan’s intellectual curiosity combined with the stamina gained from these aerobic excursions makes him a perfect personality to engage the quest of the modern wood-fire potter. Part ceramic historian and part endurance athlete, Gillan embodies the history and culture of wood firing. Honing his skills assisting the great Akira Satake and working on his own line of pots at Odyssey, Gillan strikes me as a medieval knight on a quest. Sworn to uphold and protect an ancient tradition, but seeking to tame rather than slay the dragon, Gillan operates in an interesting sphere between history and modernity.

Gillan’s work is all about maintaining control of the materials throughout his process. Gillan’s pots start with a clay body he mixes himself. He throws some very large, graceful pieces and assembles them on the wheel, but I also enjoy his slab-built plates, which I regularly use at lunch. The majority of his work is decorated with slips when leather hard and placed in the kiln unglazed to be decorated by the fire, but he also uses a traditional white Nuka glaze to great effect.

Wood firing is a labor of love and splinters, requiring endless hours of splitting, carrying, and stacking wood. The kiln itself can take several days to load before creating a fire inside it, carefully and attentively stoked, to maintain a rate of climb neither too fast nor too slow for 72 to 120 hours or more. Extreme care and coordination within the firing team is required for a successful firing. Once you unload the kiln, there remains much work to do, such as cleaning and sanding down the pots to an acceptable smoothness, followed by the dirty work of grinding kiln shelves and vacuuming wood ash out of the kiln. Another challenge is that the general public usually remains uneducated regarding wood firing. To the untrained eye, the subtly nuanced surfaces of the flame-kissed pots may simply seem to look “brown” or “old.”

So why would one undertake wood firing as a primary means for finishing one’s work? Perhaps for the same reason that Gillan runs up Town Mountain: while it takes work to get there, the view from the top is incredible. Wood-fired pottery, thankfully, has a dedicated community of collectors who understand the enormous effort required to work in this manner, and who are willing to spend more money for pots finished this way. Kiln openings in North Carolina are eventful, often starting early in the morning with a line of cars already waiting to take a look at the new wares. The most ardent collectors jockey for position to make sure they have a chance at their first choices. You’ll be served hot coffee and donuts in the morning and barbeque or something in season from the farmers’ markets for lunch. Pickers sit in a circle and improvise on blue-grass rhythms, and if you are lucky, someone with a double bass will show up to round out the sound. And in that moment, all of the hard work, the long nights of stoking, and even the splinters make perfect sense.