How to Fire Ceramic Greenware

Ceramic greenware must be kiln-fired to preserve its form.

There are several key steps to creating finished ceramic works. First the ceramic piece is either hand-built or cast in a mold. When the ceramic piece is finished, it is called greenware. It is cleaned, allowed ample drying time and cooked in a high temp oven called a kiln. When the ceramics finish the first firing, they are hard, dry and strong. This stage is called bisque. At this stage, the ceramic piece is either painted with acrylic paint or glazed. If it is glazed, it goes through a second firing in the kiln.

Things You'll Need

• Greenware
• Kiln
• Cones

Instructions

1. Clean up any rough edges before putting the ceramic greenware in the kiln. Allow the piece to dry for several days. If the ceramics were made by pouring ceramic slip into a mold, wait 4 days. Slip made for casting dries faster than regular clay. Hand-built ceramics take longer to dry--up to several weeks for larger pieces. Feel the ceramics to determine if it is ready to be fired. When the greenware feels warm and dry to the touch, it's ready for firing. If you fire it while it is still damp, it could blow up in the kiln, damaging the kiln itself as well as other pieces being fired.

2. Place dry greenware in the kiln. Do not stack greenware on top of other pieces of greenware. It needs the air to circulate, and heat everything evenly.

3. Place a cone in the kiln's sitter according to the manufacturer's instructions. Every kiln is a little different, so consult your manual. Make sure you put the correct number cone in the sitter. If your clay calls for an 06 cone, don't put in a 6. The 06 is for low fire, and 6 is for porcelain. Improperly fired clay can melt and damage the kiln.

4. Fill the kiln 3/4 full, and close the lid. Turn the kiln on the lowest setting, and let it cook for 3 hours. This will slowly dry out the clay. Turn the kiln to medium for 1 hour, and then turn it on high. Let it stay on high until the cone breaks, and it shuts off the kiln. If your kiln is manual, turn it off when you see the cone break through the peep hole. Don't get too close to the hot kiln.

5. Let the greenware sit in the kiln for several hours, or overnight. Prop the kiln open in the morning, and let it sit open for a few hours before removing the items. Use pot holders or other protection when removing the ceramic items, as they may still be quite hot.

References

• Orton: Firing Tips, Loading a Kiln for Best Results
• Orton: Firing Tips, Firing Ceramic Bodies
• Minnesota Ceramic Supply: Loading and Firing Low-Fire Greenware