Dancing with the Dragon:  Wood-firing Applied Ash Glazes in a Climbing Kiln
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Heavy ash accumulation and distinct flame markings have been the most recognizable face of American wood-firing for decades.  It is my hope that the perceived scope of wood-firing will widen to include work that takes advantage of other kinds of interactions between flame, clay and glaze that happen in wood burning kilns. 
The climbing kiln is an ancient ceramic technology whose invention was due to attempts by potters to get away from heavy ash deposits on their pots, and control events inside the kiln precisely enough to melt glazes. This innovation in Asian ceramic technology dates back to the end of the first millenium AD in China and the emergence of the Dragon kilns. The Chinese potters had been making and applying glaze to their pots for centuries already, but the ability to control temperatures within a restricted area of the kiln and achieve a narrow window of temperature to successfully melt the applied glazes was a major achievement.
            This climbing kiln design made its way to Western Japan in the mid to late 16th century, and became a mainstay in the ceramics production in the Karatsu area.  It appears to have coincided with the first use of applied glazes in that area.  The most widely seen kiln design of that time was the “split bamboo style kiln” (waritakeshiki noborigama) .  These kilns proliferated around Karatsu and present day Saga prefecture, and sometimes reached 15 or 20 chambers in length.  Shortly after the appearance of the climbing kiln in this part of Japan, there was further upheaval in the Japanese ceramics world, as Korean potters were brought over as prisoners of war and distributed among the daimyo.  These Korean potters brought with them new techniques and know how, that expanded the repertoire of Japanese ceramics considerably.
            The climbing kiln design made its next appearance in the Seto region, with the Motoyashiki climbing kiln, from about 1600.  This was a multi-chambered climbing kiln (renboshiki noborigama), which showed further refinement of design with more clearly defined chambers.  The previously dominant Great Kilns (oogama) continued to be used for some specific items, but the greater fuel efficiency and control attainable with the climbing kilns boosted it into a position of dominance.
            The Seto/Mino area is unusual within Japan for its early use of applied glazes.  The nearby Sanage kilns used applied glaze from  the 8th century AD,  while Seto potters began using glazes as early as the 12th century, and the adjacent Mino kilns took up glaze from the early 15th century.  The abilities of the climbing kiln to control and modulate temperature precisely, as well as its increased fuel efficiency was a valuable advantage for potters wanting to control glaze melting on pots.
            From around 1600, the climbing kiln design and knowledge of how to make and fire applied glazes quickly spread through out Japan.  As regions already involved in pottery production took up the climbing kiln design, local innovations or peculiarities also began to appear.  These regional potteries adjusted the design to suit their resources and needs.
            Many of Japan’s climbing kilns were still used in the 1950’s and 1960’s, but most were subsequently replaced with more technologically advanced kilns using gas, oil or electricity. The determination and resiliency of Japanese ceramic traditions, many of which utilized climbing kilns,  is seen by the numerous climbing kilns still used in some places like Mashiko.

            I set about building my four-chambered climbing kiln in 1987.  I chose the design of Tsuneo Narui’s kiln, a Mashiko style climbing kiln,  a sort of “studio noborigama” because I knew it was a proven design, and I had previous experience both  building and firing such a kiln.  I chose to build a fairly large kiln (initially about 400 cubic feet), with the intention of firing several times a year.  It was a shock to me, how much brick it required to actually construct this kiln, about seven thousand bricks .  There are certainly other designs for climbing kilns that are not such gluttons for construction materials, like Ruggles and Rankin’s kiln design, but the solid mass of a more traditional climbing kiln has several other effects.  It catches more of the ash as it passes through the kiln, and it acts as a heat sponge, slowing both the temperature climb and the cooling down.   Whether you see these as pluses or minuses depends on your aims and intentions in pottery making.
            Daphne Hatcher pointed out in a previous conference, that choosing a kiln is like getting married. My wife has a different idea, and refers to my kiln as “the other woman”, and I sheepishly acknowledge submission to my thirty ton mistress.  In retrospect I can see how once I decided on a kiln and finished construction, it directed my work in so many ways, some which were planned, and some which weren’t.  A potter and his/her kiln are partners, and mutually direct each other, as if in a dance.  It is this exhilarating, exhausting dance which my kiln and I continue, that I would like to describe here.
            Historically, one of the main reasons climbing kilns made sense is the ability to fire a large quantity of work at once, by recycling the heat through linked chambers, while controlling the temperature within each confined chamber to achieve a relatively narrow window of temperature variation.  When these kilns were used in past times, they were generally used by a team of individuals incorporating an impressive division of labor.  In my case, I do almost everything myself, except for firing the kiln which requires the assistance of friends.
            The size of the kiln can create opportunities for making large things.  In fact this may become a necessity, if you have a large kiln with a limited number of kiln shelves, a common dilemna for impecunious potters.  I also feel that making enough pots to fill a large kiln can help in building momentum in my work.  I call it momentum when I feel the repetition of making a certain form allows me to get past fussing with a form, what one Japanese friend of mine calls “too much touching”.
            One of the most daunting aspects of using this kiln, for me, is the gamble I take with each firing, which is holding several months’ potting efforts. If you have a problem with materials being unknowingly contaminated or things just go badly with a firing, you can suffer a huge set back.  Also, if you need to get things made and fired for a deadline, the turn around time is so long that it can be very inconvenient.  For this reason, I have reconstructed the fourth chamber of my kiln to function as a single chamber kiln, with about one hundred cubic feet of stacking space.  These days, I have my standard Spring and Fall firings of the first three chambers, and then subsequent firings of the fourth chamber kiln.
            I feel that wood-firing pottery is about showing how pots came to be what they are, infusing pots with a richness or flavor similar to what cooking on a barbeque does for some food.  But the clay from which pots are made and the glazes used, are just as important to me as the way pots are fired, and carry the responsibility of conveying their own personality and character.
            My clay is a mixture of Hawk Mountain Clay, Hawk Mountain being three miles from my studio, and Stancill’s Clay, from a family run clay mine seventy five miles south of my studio.  By mixing these two clays half and half, I get a sandy, iron rich somewhat temperamental clay body which can me managed on the wheel.  I like the warmth and texture of the clay, and also the way the iron and minerals in the clay effect my glazes.  I use this clay for most of my pots, except my slab plates and large jars, which are easily broken in the fire.  For them, I add about fifty percent of a fireclay based clay body.
            The glazes I use are almost all 40 to 70% ash, with feldspar and a little kaolin and silica.  I use mixed hardwood ash from our wood stove, and corn stalk ash, since our valley is filled with corn fields.  I also use some rice hull ash for a copper glaze.  I have come to find the patterns made by my glazes sliding over my forms more intriguing than patterns I put there myself.
            My early firings of this kiln, I was attempting to use sgraffito decoration on my pots, as I admired Korean pungchong pieces done this way.  I eventually got the feeling I was fighting with my glazes, so I have moved away from drawing on my pots, towards applying slips and glazes to my pots, and trying to capture the feeling of the liquid state of those slips and glazes in the finished pot.  I guess I am obsessed with the way viscous liquids cascade over solid surfaces, the drips of slip that extenuate into long finger-like patterns, and the way thick layers of glaze slowly succumb to gravity in the kiln,  moving downhill to create rivulets and pools of glaze.  I think I have been moving away from decorated pots, towards distinct, simple shapes over which I let the slips and glazes do what they will. 
            With my white slip, which is kaolin based and not particularly interesting, and my creek clay, which comes out of the little creek running directly in front of my kiln, I have tried to come up with patterns that are somewhat calligraphic, while not being entirely controlled or predictable.  Repeated squiggle patterns and a thrown grass-like pattern of the creek clay over the white slip are my favorites.  I usually fire them with a clear ash glaze, or an amber ash/clay glaze,.
            Many of the forms I throw are inspired by the shapes of fruit.  Luscious, plump peaches or pears when harvested with perfect timing, have a wonderful feeling of ripeness,  and I try to get that same sense with a ripeness of form- when a pot seems to be filled almost to bursting with a juicy succulence.
            In the past decade, I have been intrigued by the results from the hottest part of my kiln, the lower area of the first chamber, to fire large clay slabs loaded with layers of ash and creek clay glazes.  This is one of my favorite places in my kiln, and I have been trying to use the way these glazes melt and move into each other, to take on landscape-like configurations.  The Appalachian ridges that surround my home look more like waves rolling into a beach, than western mountains that rise above you in jagged formations.  By pouring swaths of thick corn stalk ash glaze on my clay slabs, and firing them hot for an extended time, the glazes slip and ooze into each other and sometimes form fascinating patterns. I think of them as ceramic Rorschach tests. The climbing kiln design brings with it the certainty of slightly hotter areas to the front of each chamber and cooler areas to the rear.  I like to take advantage of this phenomenon to fire the front of the plate hotter, creating a more melted glaze and appearance of sky or atmosphere, with the rear of the plate staying cooler and looking more like the foreground with hills and fields rolling into each other.
            I have recently been pursuing a continuation of these slab landscapes.  I have been carving patterns in the thick slabs, and firing a single thick corn stalk ash glaze on them hot enough for the glaze to begin sliding, so the glaze pools in the lowest areas and slides away from the highest areas, just as fog and clouds sometimes settle into valleys, and the ridge tops around me are exposed outcroppings of granite boulders.
            With these clay slabs, I am trying to take advantage one of the best known traits of traditional wood burning kilns, the evidence of a front side and a rear side.  Since climbing kilns are inevitably somewhat cross-draft affairs, there will be a hotter side and a cooler side, and it will probably be necessary to use different glazes in the different temperature zones.
            I like to use the differing atmospheres and effects achieved in each chamber of the climbing kiln for different glazes and forms.  The first chamber is best for reduction glazes and copper glazes.  It is not so good for my creamy corn stalk ash glaze, which is best in the upper chambers.  I also like to put the largest pots in the second or third chambers, to avoid cracking due to thermal shock during temperature climb.   I personally, don’t like to try for too many different things happening in the kiln.  I prefer to keep it simple, so I don’t get confused.
            There are also two other things that can happen in climbing kilns that can alter the pots in unique ways.  The alternating atmosphere inside the kiln each time you stoke is a very important characteristic.  In some parts of my kiln and with some glazes it can lead to liquid/liquid phase separation- a sort of oil and water phenomenon that is seen in old tenmoku bowls.  Another important characteristic of some climbing kilns is the slow heating and cooling which can lead to crystal formations in the glaze.
            Many pots coming out of my kiln don’t show ash explicit wood-fired effects. My intention is not to make pots that look deliberately wood-fired, but to make pots that have richness and depth,  not pots that grab you by the eyeballs and proclaim their naked truth,  but rather pots which exude a quiet self confidence, waiting for the viewer to discover the subtle variations and markings that remain from the transformational processes, and reveal their character over time.
            Contemporary wood firing in America has come a long way, but there is still room to discover untapped possibilities within this pursuit.  Just as historic ceramic technology evolved with the climbing kiln as a way to get beyond the heavy ash accumulations of single chamber kilns, I encourage wood firing potters to consider the possibilities of richness and depth in the subtleties of wood-fired glazed work.  We can now choose from a wide variety of ceramic technologies, antique to high tech, and I hope the spectrum of what is known as wood firing will continue to widen, and that those of us who are still young potters despite our actual ages, will continue to stretch our skills and eyes, striving for subtlety and grace in our encounters with clay and fire.  It is indeed like dancing with a dragon.

Willi Singleton
Kempton, PA
October, 2006