Leather hard is the drying stage when clay has firmed up enough to hold its shape and be handled, but still has enough moisture to carve, trim and join. It feels cool and firm, like hard cheese or leather.
What Is Leather Hard?
Clay passes through leather hard on the way from soft and plastic to bone dry. It is the stage for trimming foot rings, attaching handles, joining slabs, carving and burnishing, because the clay won’t distort when you press on it but still cuts cleanly and bonds with slip.
Potters sometimes split it into soft, medium and hard leather hard. Soft leather hard suits joining and bending slabs, medium suits trimming, and hard suits crisp carving and sgraffito. The stage doesn’t last long in warm, dry weather, so wrapping pieces loosely in plastic buys more time.
Joining parts that are at different stages, such as a soft handle on a firm mug, is a common cause of cracks, because they shrink by different amounts as they finish drying. Covering pieces and checking them often helps keep everything at the same stage. The colour lightens slightly as clay reaches leather hard, and the surface loses its wet shine.
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.