I obtain clay to make my work directly from the earth. These clays are prospected throughout Montana using geological survey maps, word of mouth, and a lot of curiosity. Each clay is unique, and its working and firing characteristics a product of the compounded geologic processes that formed it. Some are smooth, unctuous, and plastic as found while others are shale and mudstone and do not exhibit clay like properties until ground into powder.
All the clays I use require preparation. They are laid out on sheets to dry and I crush them down to a gravel with my feet or with a hammer. Then I remove large rocks and plant matter by hand. Once it is bone dry and sorted It is often ground in a hammer mill into a course powder, while others are slaked and blunged and then sieved to remove limestone or other problematic impurities. This is a very important step, one in which I am trying to find a balance between preserving the natural character of the clay and the need to refine it enough to be able to use it with some measure of confidence.
I blend various clays with one another to achieve a pleasant character in both making and firing. Course refractory clays are often blended with smooth plastic ones that have a low firing temperature resulting in clay bodies that are strong when fired at the temperatures reached in the wood kiln. By mixing it with enough water for it to flow like a liquid various clays can blend together more easily and homogeneously. This important step further improves the working properties and helps to prevent warping and cracking in the firing. The resulting slip is then poured into sheets and laid out to dry until it is stiff enough to form.
I use various forming techniques to make my work. The large pieces are coil and paddled in the manner of ancient traditions Korean and Thai jars, while the smaller vessels are either formed by throwing on the wheel or by pressing soft clay into plaster molds. Once the clay is stiff the form is often refined by scraping and carving. After each pot is done it is slowly and carefully dried so it does not warp or crack as it shrinks.
5. Wood Firing
As trees grow they absorb various elements from the earth as they grow and each species has different concentrations of such elements. These are released as ash and vapor as the wood burns. The draft created by the chimney pulls the ash and vapor along with the flame through the kiln and is deposited on the ware in the paths the flame travels. I use beetle kill pine and Cottonwood as these produce desired surfaces and are readily available in Montana.
Interesting surfaces are developed through time and temperature with each firing taking about 50 hours and four cords of wood, reaching temperatures of 2200 degrees F. This is the most strenuous part of the process in that all of the wood must be cut, split , and stacked, and the fire must be regularly stoked throughout the duration of the firing. It is also the most stressful time since the rise in temperature must be slow and steady or large pieces will crack.