Kiln

Kiln, oven or furnace usually designed for “firing” earthy materials to make bricks, pottery, or quicklime. Limestone for quicklime is often roasted in a shaft kiln, being heated by hot gases flowing upward as it falls through the shaft. Clay and limestone, used to make cement, are usually burned in a rotary kiln, a long tube (up to 610 ft/186 m) that rotates slowly. The materials are heated as they shift gradually along it. Bricks and pottery, stacked on small cars, may be fired continuously in a tunnelkiln. The clay is prewarmed and hardened as it approaches the center firing zone and gradually cools as it leaves. Clayware is also fired in batches in periodic kilns. Ware is stacked, heated, and allowed to cool before repeating the process.

See also: Pottery and porcelain.