Nothing effects the quality and beauty of a pottery vessel more than its body clay. I would dare say that it is even more important than the potter himself for without decent clay what can the potter achieve? Patience has been a hard lesson for me to learn, my inclination from the time I first started in pottery as a teenager was to rush everything. Hurry in selecting clay, hurry in processing the clay, hurry in refining minerals and preparing tempering and building and firing and everything. Obviously the results were not so good and in this way, over time, pottery has taught me to act carefully and deliberately. I have found that the more care taken in the foundation of my work, the careful selection and preparation of materials, the finer the results. It is easy to think of the body clay, (what archaeologists call the paste) as not requiring as fine a quality as the slip or the paint, but that is not the case, quality starts at the very foundation and is built up as slip and paint are added.
Some pottery producers are blessed with naturally fine clay and that is reflected in the quality if their wares. Notable examples of this are Hopi and Mata Ortiz, even going back to prehistoric times in these areas you will notice the exceptionally fine quality if their pottery. Others of us are not so fortunate. Here in Southeast Arizona there is an eclectic variety of clays, both sedimentary and residual, in a wide variety of colors and textures, but finding the finest clay and temper requires a lot of searching and experimenting.
Take the well know “Vail clay” for example. It is easy to access and dig and if you ask people about native clay in the Tucson area someone will invariably mention it. But these things have nothing to do with quality. The Vail clay is quite ordinary, perhaps less than ordinary, it’s best quality is its accessibility, in an evaluation of 20 Tucson area clays for an archeological project, Laurel Thornburg described it as “not promising” and “difficult to work” and yet it remains the most well know and popular of native clays in the area. Consider the ancient lakebed formations in the area around Benson, Arizona, the thick pink clay beds that are highly visible around that area are a known source of clay, but there are dozens of lesser known, smaller and less colorful clay deposits in that region that hardly anyone seems to know about.
It takes a lot of exploration and experimentation to figure out where the truly exceptional clays are located, and once you find a great clay source there is still the question of tempering. Tempering is necessary to keep your clay from cracking, but it effects more than that, the coarseness of your temper is a major factor in the ability to smooth the surface of your vessel. I have tried everything I could get my hands on natively in this area for temper, wash sand, ground stone, ground pottery shreds, always striving for finer and finer texture. I always envied the New Mexico pueblos and their “Pojoaque sand”, volcanic ash, as it creates a body clay with so fine a texture that it can be sanded and carved without leaving chunks of temper standing out or pits where it had been. Even better than Pojoaque sand though is Hopi and Mata Ortiz clays which naturally contain volcanic ash and don’t need anything added. I have experimented with volcanic ash deposits in my area, but none seem to have the correct makeup, generally being difficult to grind and separate the powder from the larger chunks.
Eventually, after much exploration, I discovered a smooth and plastic clay in the Benson area that works very well. So far I haven’t found a source of it near a road, so I have to pack it across a quarter mile of desert on my back, but it’s a small price to pay for good clay and I am hopeful that I can find a deposit near a road eventually and that I will be able to get permission from the land owner to use it when I do. I almost gave up on finding a great source of temper, then I discovered that we had a rare mineral here in Southeast Arizona that might work, a mineral that might even work better than volcanic ash. The San Pedro Valley contains at least a couple of deposits of Diatomite, fossilized remains of diatoms, a type of hard-shelled algae, this mineral is much rarer that volcanic ash so examples of its use as ceramic tempering are few but not unheard of. It is fine grained, easily ground, angular so it grabs the clay well and best of all, it seems to give my clay a smooth, buttery texture.
The quest for the perfect body clay has taken me a long way, over the deserts and mountains of Southeast Arizona, and over many years. But I seem to be making progress and that makes me feel good about it. I have some firing tests coming up which will help me make some determinations about clays and temper, so stay tuned for information on that.