What is leather hard clay?

Leather hard is a stage in the clay drying process where the clay has lost most of its moisture, but is still slightly flexible and can be carved or trimmed. Leather hard clay is generally stiff and hard enough to handle, yet soft enough to be easily carved or trimmed with a knife or other sharp tool. This stage is important for building complex or delicate structures as it allows one to carve and trim the clay before it fully dries and becomes rigid. After the leather hard stage, clay becomes bone dry and finally fired in a kiln.