Without getting technical, clay is a type of soil that
Most everyone knows what clay is. You just have to find some. It really is a rather abundant earth material. One will most often easily find clay along stream banks, ponds, and road cuts. If wet when found, a step and time is saved. Just dig back into the vein a bit to get away from the surface debris(that will only have to be removed), and dig it up. If dry, it needs to be re-wetted. Lots of ways to do this.
What most good potters do is to pound/grind up the clay before adding water to allow for better absorption. Add enough water to completely dissolve the particles to make a "slurry" solution. You want it kind of thin, which will allow you to stir the solution well. Let it set for 20-30 seconds to allow the heavier stones etc. to settle and then carefully pour off the thinner, silty clay solution into another container. This can be repeated if necessary. Once amost of the impurities appear to have been removed, the container should be set aside to allow the heavier clay to settle. The lighter water should occasionally be poured off. This can take several days. As the clay begins to thicken, it can be spread out on a smooth surface for drying. When it reaches the right consistency, it is ready to use. If you are in a hurry, you can mix the water and clay, kneading and working it until it's "right", feeling the larger impurities and removing them with your fingers. This is OK for smaller, quickie bowls, but it is believed that the longer the clay sits wet, the better.
For working, the moisture content must be "just right". Too wet and it will be too sticky and will slump, not holding its shape. Too dry and it will crack as you work it. If a little too wet, it can be worked in your hands. This additional working is good for the clay, most notably removing pockets of air. Alternatively, it can be spread out, allowing the sun or wind to dry it. If the clay is just a little bit dry, dipping your hands in water, shaking off the excess and working the clay works well.
Not all clays will work! A good simple test is to roll it pencil thin and tie it into a knot (like a pretzel). If it doesn't break or crack, it's a good candidate. Plasticity is the key. The amount of shrinking during drying is also an important factor. Too much can hurt. The addition of "temper" can sometimes help here. Some clays may have all the outward characteristics of a good clay but blow apart when being firing. If you follow all the instructions and still have firing problems, change clays.
Offered by Steve.
Source: Primitive Wilderness Living & Survival Skills by John & Geri McPherson, $24.95.