© 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.
The green ware, dry, but still fragile clay, once bisque-fired, becomes durable ceramic. It is then cooled slowly to prevent cracking or shattering, and is subsequently decorated and coated with glazes of various formulations that vary to create specific finishes and colors. When re-heated carefully one or more times for applications of one or more glazes, the surfaces melt completely, leaving the surface flawless, glassy, waterproof, and extremely durable.
Utilitarian tiles of all descriptions and industrial parts, fittings, nozzles, and accessories of all kinds can similarly be manufactured from clay and other materials using a kiln.
Ceramic items whether high-grade porcelain, stoneware, or lowly earthenware, are highly durable and can last for centuries –all because of a kiln. That’s why K is for Kiln.
Is that Incoming I hear?
1. Photo: A Paragon electric kiln
2. Photo: Greenware by author