© 2013 Raymond Alexander Kukkee
K is for Kiln. Handy, but especially useful for the crafts-oriented individual, a kiln can be used to make glass, form and cast glass, melt metals, apply melted glazes, and manufacture ceramic and porcelain articles of all types. Yes, you too can make your own unique ceramic coffee mug, pottery, teapots, dishes and decorative ceramic art if you have access to a kiln.
A simple kiln can even be constructed, building an enclosure made of clay or loosely-assembled fire brick. A kiln may be heated with any available fuel source including electric heating coils, wood-fired, natural gas, or coal. Many commercial models of kilns are available.
In operation, kiln temperatures of over 2500 F (1400 C) can be achieved. The temperature is carefully controlled to a specific rate of increase and the final temperature desired is predetermined by the characteristics of the clay or porcelain being used.
Temperatures are controlled with 'kiln sitters' which themselves may be electronically controlled by using 'cones' which melt, at a specific temperature, dropping a mechanical switch and shutting down the kiln heating system when the desired temperature is achieved.
With the temperature carefully controlled, dried clay objects called 'greenware' are bisque-fired, brought to high temperature to bake and cure the clay body. Depending upon the characteristic chemical content of the clay body itself and the temperature achieved in the kiln, components of the clay melt and fuse in a process called vitrification. Vitrification begins at approximately 1450 F (700 C) and carbonaceous materials in the clay body burn off.
Clay bowls - Green ware awaiting firing in the Kiln
Way cool! How big is it? How big an object do you suppose you can place within it?
Hi Glory, these kilns come in various sizes. I have one that will accept 3 or 4 layers of the greenware bowls like those of mine shown in the photo, the kiln is about 28″ deep by 26″ across. You can get much bigger or much smaller kilns. You separate the layers of greenware with ceramic shelves that are coated or washed with “kiln wash” to prevent the bowls or melted glaze from sticking to the shelves. The shelves are separated by vertical ceramic separators. If it’s all hardened, dried greenware, you can stack it for low fire bisque firing without separating by shelves if the pieces are not too delicate. For glazing, the pieces must be separated by shelves and mounted on ‘kiln feet’ so the glaze doesn’t melt from the piece and stick it permanently on other pieces or on the shelf.