What Are the Stages of Clay?

By Nina Hughes ; Updated September 15, 2017
Clay goes through many forms before it is used for sculpting.

Clay is formed by dirt particles that get wet and stick together near mountains and riverbanks. It is used to construct decorative pieces such as pots, vases and sculptures and then fired in a kiln to fully harden. It goes through several stages before it is ready to be fired and then painted or glazed for decorating.

Raw

Clay is in a reddish raw form to begin with. It is mostly found in mountain areas near rivers where the dirt is pulled to the ground by gravity. Small particles of dirt become soaked and absorb together, turning into a soft pliable substance known as clay. This is in its rawest form. Raw clay can also have a purple, black or gray look to it.

Slip

Raw clay that has water added to it turns into what's known as slip. It takes on a wet, mud-like texture and is very soft. It is similar to the feeling of toothpaste. Slip can be used like a glue substance in sculpting to add appliques and clay embellishments to already dried out clay. It is also used to create the glaze painted on over clay art after it has been in the kiln.

Plastic

The plastic stage of clay is the most known. This is where artists play with the clay to form, mold and sculpt pottery and artistic pieces. It is easily workable and can be recycled if the sculpture is not desirable. This is also the stage it is used on a pottery wheel. Artists use pinching, coiling and slab techniques to sculpt the clay into pots and sculpture designs.

Leather-Hard

When the clay ages and dries out after sculpting is done, it is known as leather-hard. It feels like hard cheese in this stage. This is when artists can carve designs in their clay work and add features and decorations to the outside of the sculpted clay. It is sturdy enough to withstand pressure without collapsing. It can also be made into plastic again if it is soaked in water for a few days.

Bone Dry

This is the most delicate stage as the clay is extremely dry and all the water has fully evaporated out of it. Not handling clay art carefully can result in it breaking. Bone dry clay is also known as greenware since it turns a greenish color as it dries. The reddish hue fades from the clay the more it dries out. It can still be recycled by soaking it a long time in water to regain its moisture.

Bisque

Clay is in the bisque, or bisqueware, stage after it has been fired in a kiln once. It is still porous, but cannot become soft again if water is added to it. No additional clay pieces are able to be added to the design after it's been fired once. The firing of the kiln fully hardens the clay and this is the time when the sculpture can be glazed.

Fired

This is the final stage when the clay is put in the kiln again. The glaze is painted on the pot or sculpture to add a shine over the art. The second firing in the kiln hardens it and completes the art. At this last stage, it is also known as stoneware. It is not able to be softened again or recycled back to plastic form.