October 25, 2013

Clay on the Wild Side: Processing Locally Mined Clay

For the past month, I’ve been slowly mining and processing local clay. I try to tell myself that by using local materials I not only save money but help keep the planet green by not ordering clay that is machinery mined elsewhere then shipped. But in fact I am really fascinated by the process of foraging for raw materials in nature and making things entirely from scratch. The clay that I processed above is in slightly different hues depending upon what part of the clay vein it was mined from. It is clay from the wilds. Collecting it feels like harvesting wild berries or acorns for food.

Every one of these lovely lumps of clay is a natural color except for the large cone shaped piece. That one wasn’t quite dark enough so I added some red and yellow ochre pigments that came from Italy and Southern France. So that piece is an international clay body. Actually all the clays have some additions to them to strengthen them or make them more plastic. My intention with these wild clays is to pit fire them unglazed so that the natural clay color can shine through.

In processing the clay by hand I soon learned just how tedious this could be - mostly because I had been doing it the hard way by letting the clay dry out, then pulverizing it and sifting. It took forever. After doing some reading and with the help of an expert on Etsy, I learned that the wet method of processing the clay is by far superior, cleaner and faster.

The first step is to wash off the surface debris from the clay then break it into smaller pieces. These pieces are then softened under water in a large bowl or bucket - about half clay to water. After softening a few days the clay is then mixed to a smooth and creamy finish. I used an old blender to do this. In the blender, I add a small amount of volcanic ash for clay strengthening and a small amount of ball clay for plasticity. My colleague on Etsy uses a drill that is fitted with a mixing tool (found in the paint section of Lowes) which probably goes faster and would be much easier to clean. The resultant slip is then left to settle. After siphoning off water from the top, the thickened middle part of the slip is run through screen that is 80 mesh or higher. I use a very fine mesh that not only removes sticks and stones but heavier sand as well. The slip is usually a little too thick to just run through on its own so I squeeze it through the screen with a stiff paint brush.

I let the sieved clay slip settle again for a few days, then siphon off the water that accumulates at the top. The slip is then spread out onto thick plaster bats to dry. (These can be easily made by pouring plaster of paris into old aluminum casserole trays or in larger plastic trays - but be certain to grease them first so that the hardened plaster can release. ) Sometimes I hasten the drying process along a bit by leaving the slip on the plaster to dry out in the sun. Depending upon whether the drying slip is indoors or outdoors and the humidity, it can take one to two days for it to become ready to roll up and wedge. That’s the fun part, when it finally feels like Free clay, despite the time to gather and process the stuff.

The final step is to wrap the clay in plastic bags - supermarket bags will suffice. For extra caution against drying out I put the plastic wrapped balls of clay into a large plastic bucket with a lid. The lid is marked “Wild Clay.” But before packing it up I like to meditate on it for a short time, envisioning the sculpture and vessels that will be produced from it. I pack those visions up with the clay - letting both season a while.

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