Coning is pushing centred clay up into a tall cone on the spinning wheel and then pressing it back down, once or several times, to even out the clay, work out lumps and air, and help it run true before you open it.
What Is Coning?
To cone up, you squeeze the base of the clay inwards with both hands so it rises into a cone, then use one hand on top to press it back down into a low mound. The spiralling movement of the clay mixes it, a little like wedging on the wheel.
Coning helps clay that is slightly uneven in softness, and many potters find it makes centring easier and more consistent. It also aligns the clay particles in a spiral, which some teachers believe reduces the chance of S-cracks in the base.
Overdoing it can tire out the clay, making it soft and floppy, and some potters skip it entirely when their clay is well wedged. For beginners it is a useful exercise in controlling clay on the wheel, even before the piece itself is thrown. Two or three cones are usually plenty, and a little water on your hands keeps the clay from dragging as it rises and falls.
This pottery glossary entry from Le Studio Art Space is general educational content. Always follow the clay, glaze and kiln makers’ data for your own materials and equipment.