The word 'kiln' was originally pronounced 'kil' with the 'n' silent, as is referenced in Webster's Dictionary of 1828 and in English Words as Spoken and Written for Upper Grades by James A. Bowen 1900: "The digraph ln, n silent, occurs in kiln. A fall down the kiln can kill you." Bowen was noting that "kill" and "kiln" are homophones.

Pit fired pottery was produced for thousands of years before the earliest known kiln, which dates to around 6000 BCE, and was found at the Yarim Tepe site in modern Iraq. Neolithic kilns were able to produce temperatures greater than 900 °C (1652 °F). Uses include:
• Annealing, fusing and deforming glass, or fusing metallic oxide paints to the surface of glass
• Heat treatment for metallic workpieces
• Ceramics
• Brickworks
• Melting metal for casting
• Calcination of ore in a rotary kiln prior to smelting
• Pyrolysis of chemical materials
• Heating limestone with clay in the manufacture of Portland cement, the cement kiln
• Heating limestone to make quicklime or calcium oxide, the lime kiln
• Heating gypsum to make plaster of Paris
• For cremation (at high temperature)
• Drying of tobacco leaves
• Drying malted barley for brewing and other fermentations
• Drying hops for brewing (known as a hop kiln or oast house)
• Drying corn (grain) before grinding or storage, sometimes called a corn kiln, corn drying kiln
• Drying green lumber so it can be used immediately
• Drying wood for use as firewood
• Heating wood to the point of pyrolysis to produce charcoal
• Extracting pine tar from pine tree logs or roots

Kilns are an essential part of the manufacture of almost all types of ceramics. Ceramics require high temperatures so chemical and physical reactions will occur to permanently alter the unfired body. In the case of pottery, clay materials are shaped, dried and then fired in a kiln. The final characteristics are determined by the composition and preparation of the clay body and the temperature at which it is fired. After a first firing, glazes may be used and the ware is fired a second time to fuse the glaze into the body. A third firing at a lower temperature may be required to fix overglaze decoration. Modern kilns often have sophisticated electronic control systems, although pyrometric devices are often also used.

Clay consists of fine-grained particles that are relatively weak and porous. Clay is combined with other minerals to create a workable clay body. The firing process includes sintering. This heats the clay until the particles partially melt and flow together, creating a strong, single mass, composed of a glassy phase interspersed with pores and crystalline material. Through firing, the pores are reduced in size, causing the material to shrink slightly.

In the broadest terms, there are two types of kilns: intermittent and continuous, both being an insulated box with a controlled inner temperature and atmosphere.

A continuous kiln, sometimes called a tunnel kiln, is long with only the central portion directly heated. From the cool entrance, ware is slowly moved through the kiln, and its temperature is increased steadily as it approaches the central, hottest part of the kiln. As it continues through the kiln, the temperature is reduced until the ware exits the kiln nearly at room temperature. A continuous kiln is energy-efficient, because heat given off during cooling is recycled to pre-heat the incoming ware. In some designs, the ware is left in one place, while the heating zone moves across it. Kilns in this type include:
• Hoffmann kiln
• Bull's Trench kiln
• Habla (Zig-Zag) kiln
• Roller kiln: A special type of kiln, common in tableware and tile manufacture, is the roller-hearth kiln, in which wares placed on bats are carried through the kiln on rollers.
In the intermittent kiln, the ware is placed inside the kiln, the kiln is closed, and the internal temperature is increased according to a schedule. After the firing is completed, both the kiln and the ware are cooled. The ware is removed, the kiln is cleaned and the next cycle begins. Kilns in this type include:
• Clamp kiln
• Skove kiln

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