Susan Mulroy Ceramics, Ceramics and clay workshops


Raku Kiln Building

Living with Clay

What gives people inspiration for life? What motivates us to get out of bed in the morning? After dropping out of college at 19 I spent a few directionless years until I discovered the malleability, the sensitivity, the memory of clay. Clay is of the earth, it takes us back to our roots. The squishing and squashing, wet clay oozing through fingers, evokes memories of preschool fun, of mud baths in granny's backyard, times of freedom, when responsibility was light on our shoulders. Clay, in contrast to a lot of other art mediums, releases its inspirations at the slightest touch, as if it is impatient to become interesting, even the preparation of clay has its own beauty, each rhythmic movement leaving its own melody on the clay. I was motivated to make pots, to give them personality, to permeate them with my creative pleasure so that they might pass on that sense when long gone from my hands. I love the permanence of clay as much as it's flexibility. Whether you're a complete beginner or the most skilled potter in the world, there is an amazing feeling of accomplishment and satisfaction to be found in working with clay. I was besotted.

Making pottery takes you into a world apart, people from all walks of life - artistic, scientific and therapeutic - have been bitten with the bug of working with clay. It is accessible, there are no fine art boundaries to clay work. The pliability and immediacy of the medium transports the user into another land and the would-be ceramicist enters a fantastic world of form, surface and pattern, where the skills of construction must be mastered and the potential of surfaces is glimpsed. Finally each piece is subjected to the metamorphic ravages of fire. The results can be unexpectedly magical, or painfully disappointing - discovering that the fruits of your long labours have been reduced to a pile of shards is not easy.

My first experiments with glazes were a complete failure . During those first few months of working with clay I had to develop an entirely new set of skills than the ones I had acquired from my scientific education. These were skills of intuition, creativity and instinct. To connect with my new gifts I had to let go of some of my old concepts, feel the rhythm of the medium I had chosen and give my confidence the chance to grow. The process reminded me of cooking. Each ingredient of a glaze has an individual and combined effect on every other. Add to that the impurities that are a natural part of the raw materials, then consider the various effects of temperature, fuel, kiln atmosphere, weather and suddenly the complexity of the process is clear. The gripping nature of the clay bug becomes clear too - it is a never ending learning experience, in ten lifetimes there would still be more to learn. Recently I heard of a Japanese potter who fires in a traditional wood-fired Anagama kiln. His work demonstrates a precision developed from generations of experience. He is layering ash to create his glazes, but these ashes are fed into the kiln as wood fuel, and he must carefully balance temperature, atmosphere, and fuel over many days to get the fly ash to ride the flame through the kiln and to achieve the desired results. This is a pinnacle of firing control beyond my wildest dreams.

This year, in a new venture, I returned to making things from the earth using clay. I decided to move away from my old wood ash and salt glaze high-fired roots, and venture into the low-fired world of Raku:

"Raku, a firing technique that involves taking a hot pot from the kiln and manipulating its environment to obtain exciting glaze surfaces"

Making that metamorphic transformation from the malleable, transient medium of clay to the stone-like, permanent structure of ceramic only requires temperatures achievable in a hot bonfire. The colours and surfaces that can be achieved at these low temperatures are stunning, but the finished pots are much softer and more porous, and, inevitably, less functional than higher fired work. This meant a fundamental change in the character of the pots I make - my work was originally dictated to by function. Suddenly the restrictions had disappeared and my work had no such constraints. I was about to fly with no safety net!

One advantage of making Raku is that kilns can be constructed to a much lower specification than for higher fired work. A very basic raku kiln can be assembled using a burner, a metal bucket and some ceramic fibre insulation. I began to research the possibilities, looking at potential insulation materials, considering the benefits of various frames. Many kiln frames can be constructed of found or waste materials like an old oil drum or open metal mesh. Raku kilns only need a support for the insulation, the relatively low temperatures that need to be achieved make a more robust structure unnecessary. Armed with a basic knowledge of kiln building, and a lot of information gleaned from books, I began to search for my materials.

Size does matter when it comes to kilns, and is the first decision that needs to be made. I had to think, 'what do I need from my kiln?' I knew that although I had a good knowledge of different firing techniques and the principles behind them, my Raku firing experience was very sketchy and a small kiln would enable me to fire frequently and get lots of feedback. Also, I wanted to take the kiln out to workshops so others could be inspired by the flame and smoke of raku so it had to be portable. The final consideration was ease of use - although a raku firing can be a great social occasion, I live alone, and need to be able to fire alone, and so my plan was to build a small, portable, user friendly kiln. It would restrict my ability to make larger pieces, but there would always be another day to build again.

Once the size had been sorted, shape was next . Square or round? Instinctively I felt that curves would help the flame move through the kiln, but had heard great reports about a square mobile kiln designed by Ian Gregory. It consists of a wire mesh frame lined with strong aluminium cooking foil, held together with strong crocodile clips. It's very portable, and much more easily packed than an equivalent oil drum kiln. Additionally, it is possible to remove both a side and the lid to allow easy access during firing. I considered creating a hybrid kiln, using the mesh frame in a cylindrical structure but I had an old metal drum handy, and, being a recycler by nature, I decided to use what was at hand. Rather than making a separate lid I built a top hat construction so that the whole kiln is lifted away from the base when temperature is reached. I cut the burner port and flue using an angle grinder, attached handles and made holes in case buttons were needed to support the fibre. Finally a couple of hours graft saw the old paint removed and a fresh coat of stove paint applied.

Insulation came next. The obvious choice for a small, portable kiln like this is ceramic fibre blanket, which created a revolution in kiln design when it was used by potters in the 60's and 70's. One inch of fibre gives the equivalent insulation of 4.5 inches of high temperature insulation brick. Unfortunately, after being freely used for many years, it was found to be carcenogenic as well as a skin irritant. A new body-soluble fibre is now available, which has fibres small enough to be dissolved in the lungs. This is a great improvement, although still needs to be handled with gloves and mask and treated with respect. The surface of the fibre can be treated with a rigidiser, sodium silicate solution, to make it less likely to lose fibres during the firing, so I did some research, and found a local refractory company that were willing to give me some sodium silicate impregnated ceramic fibre. I hadn't seen any evidence of this material being used for a Raku kiln before, but I'm not shy of experimenting, sometimes to my detriment, and this is part of the wonder of kiln building, my kiln, my choice of materials, and inevitably, my mistakes!

Working with this material was like trying to make a snowman out of powder snow. It was wet and much more fragile than other blanket I'd used previously. It needed "setting" with a blow torch between layers and the layers were only ¼ inch thick. Because it was soaked with rigidiser it was self supporting once set, but keeping it in the right place until I could get the blowtorch on it was an art - definitely easier as a two person job! After 5 layers I ran out of blanket, I'd have preferred to have used 6 or 8 layers but that had to do. The kiln was beautiful, the blanket still looked like snow, as if a brilliant white drift had settled inside my kiln.

All that was needed now was a heat source. I already use an old propane gas kiln built by Ben Casson so I had gas bottles and a store in my yard, I just needed to swap one of my 47kg bottles for a smaller, portable version. Although I had some AMAL gas burners from an old salt kiln, they were anything but portable, and the stoneware kiln has lovely pot burners - ideal for a raku kiln but they are fixed and so I decided to make a whole new unit for the raku kiln. In retrospect, my self reliance stopped me seeing the best solution. There are now some complete burner and regulator sets available from pottery materials and kiln companies. The saving made by buying the parts was minimal and unless gas plumbing is already a known skill, I would recommend buying a ready made burner unit.

At last, I was ready to fire! First I enlisted the help of Jo Bunberry, a friend with raku experience, and we launched into the adventure. We used some offcuts of cast insulating refractory material as a base for the kiln, but high temperature insulation bricks would have worked just as well. Initially I chipped down an old kiln shelf to use as a shelf above the burner inlet but this impeded the flame flow through the kiln. The learning curve was steep, the first firing was slow, with the heat becoming trapped in the lower part of the kiln below the shelf. We removed the shelf for the second attempt, placing the pots in a spiral ascending up the kiln, and with the insulation now crisp and dry the temperature rose more rapidly.

After removing the pots from the hot kiln with tongs we used straw, sawdust and water to reduce and quench our pots. Overall I was pleased with the performance of the kiln, the results were interesting, and there are endless possibilities for fuming and smoking to manipulate the results. I was a little concerned about the longevity of the impregnated fibre insulation, the rigidiser made the blanket very brittle, so although the new material created less airborne particles of fibre, the lining was very prone to damage with the slightest knock.

The highlight of my year was the second firing in the new raku kiln. Unintentionally alone with the kiln, I persevered in building up my relationship with this new "partner". Darkness fell as I was still struggling to balance heat, atmosphere and fuel, to try and generate the optimum temperature rise. I resorted to using my Christmas lights to illuminate my labours. A flood the previous month had relegated my soft, comfortable sofa to the yard. With real pleasure, I put my feet up and surveyed my new venture. At last, I felt I was tuning in to the subtle nuances of the firing, my back yard empowered by a glowing spaceship of a kiln and the subtle illumination of the string of fairy lights. I felt transported to a world of magic and fire, in touch with my creativity, my life, and the world.


Copyright 2004 Susan Mulroy ©