How to Fire Pottery in a Kiln
You've put in some hard work, dealt with some trial and error, and now your pottery masterpieces are ready for the next phase. The pottery-making process usually requires two different stages of kiln firing: bisque and glaze.
Things You'll Need
- Green pottery pieces
- Kiln support posts
Allow the pieces to dry completely after construction. Any trimming and moderation should be performed when the clay is in the leather hard stage. Afterward, it should be placed on an open surface and left alone for at least two days. The actual length of time will vary according to the size of the piece and the thickness of the clay.
Section your fully dried pieces together by height for bisque firing (which will take place in an electric kiln). Place the initial support posts inside the kiln. They should be a fraction higher than the tallest piece of pottery in the first layer.
Place your initial pottery pieces in the electric kiln, around the supports. After the first layer of pots are in place, shelves are put on top of the supports for the next layer of pottery. Repeat these steps until the kiln is adequately filled.
Set the appropriate firing time and temperature on the kiln. For the bisque firing process, the general temperature will be about 1750 degrees, also known as cone 07. This term refers to the clay test cones placed in kilns which melt at various temperatures. Allow the pieces to bake in the kiln for roughly 18 hours.
Remove the pieces from the kiln (once they are at a temperature which allows safe handling). Allow the pieces to sit undisturbed until they have cooled completely.
Wipe each of the pieces with a damp sponge before glazing to ensure that dust and debris have been removed.
Glaze your pottery and allow to dry undisturbed on a shelf, counter, etc. Since glaze firing is a long and precarious process, it is recommended that the final firing wait until there is enough glazed pieces to substantially fill the glaze kiln.
Load the glazed pieces carefully into a glaze kiln (typically outdoor or gas-powered). Unlike the bisque kiln, the glazed pieces cannot be touching in the glaze kiln (as the pieces may stick if the glaze runs). Some people prefer placing the glazed pieces on small planks to protect the shelves of the kiln. Pay attention to the temp. requirements of each glaze, as it will determine where the pieces should be placed (the bottom of the kiln is hotter than the top levels).
Begin firing the kiln at an average temperature of 2300 degrees. Too much variance can cause a variety of damage to the pottery (too cold and the glaze won't melt properly; too hot and the glaze will run too much). Fire the pieces for an average of 18 hours.
Allow the kiln to cool for 2-3 days before removing the finished pieces.
- Do not open the glaze kiln door during the firing process! Even opening the door a crack can cause a change in temperature severe enough to destroy much of the pottery within.