Clay is hardened traditionally by firing it in a kiln, a special oven that heats clay from all sides at high temperatures simultaneously. However, there are also special formula clays available that self-harden without heat or that can be heated in an oven.
- Identify the style of clay that you are working with
Determine whether you are working with traditional clay that needs to be fired in a kiln, self-hardening air-dried clay, or clay that is designed to be re-sculpted, such as Crayola.
- Prepare the clay for hardening
If you are using traditional clay, it needs to be fired inside of a preformed mold. If you are using self-hardening clay, it should be sculpted prior to drying to achieve the desired form. Reusable clay such as Crayola is not designed to harden and should not be heated.
- Fire or air-dry the clay
Once a mold has been filled with traditional clay, it can be fired in a kiln until it dries out and hardens. Allow self-hardening clay to dry out according to the manufacturer instructions.
- Remove the clay from the mold
Allow the clay to cool and return to a safe temperature before handling the mold to avoid cracking or breaking the dried clay.