A kiln is the heating chamber in which clay is "fired" - or heated - to irreversible hardness. The chemical reaction that turns the clay into a hard material requires a temperature of 1900 degrees and more. Usually tiles are fired twice. The first, a "bisque" (short for 'biscuit') firing, hardens the tile. The second, a glaze firing, melts and fuses the glaze onto the tile surface, resulting in a smooth, glassy coating. When a decorative effect is desired, glazes are hand painted onto the tile after either the bisque or the glaze firing, and the tile is then fired again. This firing can take up to 24 hours, including the cooling period. The temperature in the kiln must be decreased very gradually to ensure the integrity of the finished tiles.
Each mural may be fired up to 3 or 4 times before complete.
I have three kilns, ranging from very small to very large. My smallest kiln is perfect for firing just a few tiles, while the largest can handle 12 square feet of tiles, ideal for large murals. Bigger murals may require several individual firings.
After I have painted the mural onto the tiles with glazes, I load each tile into my kiln. The mural is then fired to approximately 1900 degrees Fahrenheit, resulting in a rich, visceral, permanent piece of fine art. When the mural has reached my satisfaction, it is carefully packed up and shipped directly to the client. Each tile is marked on the back to ensure ease in putting it back together correctly.
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