Firing, Part 1
In order to transform a dry, brittle piece of greenware into a hard, durable ceramic object, it must be subjected to enough heat to "mature" the clay; for most clays used in hobby ceramics, the maturing temperature ranges from 1830° to 1940°F, and the firing is done in an oven that is called a "kiln," pronounced with or without the "n."One of man's earliest tools was a kiln, in which to fire his ceramic wares. The first kilns were merely shallow depressions in the earth, into which clay pots were placed and a fire was then built over them - a process still utilized by some of today's primitive peoples. Obviously, such kilns afforded very little control over the intensity of the heat, and firing in them was a chancy procedure, resulting in poorly fired, porous ware and a high percentage of broken pieces. The temperature in these open kilns very rarely exceeded a dull red level (about 1530°F), since there was no way to retain the heat. As the demand for pottery items for utilitarian use - and later for decoration — increased, more efficient kilns were developed.
Most kilns today are fueled with gas, oil or electricity, the gas and oil fired kilns being used for high-fire and commercial work. The majority of hobby ceramists fire their wares in electrically heated kilns, which are a fairly recent addition to the catalog of kilns used over the centuries. Electric kilns did not become practical until the development of lightweight refractories (heat-resistant materials), in the late 1930V Since World War 11, great strides have been made in the manufacture of quality electric kilns at reasonable cost (both to purchase and to operate), so that an electric kiln is now within the reach of almost any ceramist and nothing in ceramics equals the satisfaction and thrill of firing your own creations.
May 19, 2012