How to Harden Pottery Clay

Harden a piece of pottery clay in a kiln.

Pottery clay is used to make items such as mugs, plates, pots and wall decorations. The clay itself is harvested from the earth and processed to remove debris such as rocks and twigs. An item made with pottery clay dries to a greenware state than is hardened in a kiln. The greenware state removes the moisture from the clay and makes it very fragile. Heating the clay to an optimum heat will remove the remaining moisture and create a piece of bisqueware. Bisqueware is hard and ready for glaze or paint.

Things You'll Need

• Completed pottery clay item
• Kiln
• Paint
• Glaze

Instructions

1. Place the completed pottery clay item on a shelf to dry. Check the clay periodically by placing the clay against your cheek. The clay is cold during the drying process. It will be room temperature when completely dry. The pottery item is now called greenware.

2. Place the greenware into the kiln and close the kiln.

3. Set the kiln to the appropriate cone level to harden the clay. Each clay body has a different cone number. A general firing that is good for most clay is Cone 6 which is a medium fire range. The temperature ranges between 2165 and 2269 degrees Fahrenheit.

4. Allow the kiln to cycle through the firing process and cool completely.

5. Remove the fired pottery clay item from the kiln and process with either paint or glaze.

Tips & Warnings

• For individuals without a kiln, pottery clay may be fired in an open fire pit. The pottery item is placed in the center of the pit and surrounded by stone. The top must also be covered by stone. The fire must remain very hot for a minimum of six hours. This is a time consuming process and requires an extreme amount of wood, but is possible.

References

• Big Ceramic Store: Cone Chart