Trimming is shaving excess clay from a thrown pot once it is leather hard, usually upside down on the wheel, to refine its shape, even out the walls and carve a foot ring. In Britain it is also called turning.
What Is Trimming?
When you throw, you leave extra clay in the base so the pot can be lifted and handled. Trimming removes that clay. The pot is centred upside down on the wheel, held in place with small lumps of clay or a trimming chuck, and a sharp loop or trimming tool shaves away curls of clay as the wheel turns.
The right stage is medium leather hard: firm enough to hold its shape when pressed, soft enough to cut cleanly. Too wet and the clay smears and distorts; too dry and it chatters and is hard work. Tapping the base and listening for a hollow sound tells you when the base is thin enough.
Good trimming makes the outside follow the curve of the inside, so the wall is even all the way down. That makes pieces lighter, look more refined, and dry and fire more evenly, reducing cracks.
Many potters find trimming relaxing once they are comfortable with it, and it is where much of a pot’s character is set.
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.