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How does a tunnel kiln fire large quantities of traditional ceramic products?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
Stages in the slip casting of a thin-walled whiteware container. Clay powder is mixed in water together with a dispersing agent, which keeps the clay particles suspended evenly throughout the clay-water slurry, or slip. The slip is poured into a plaster mold, where water is drawn out by capillary action and a cast is formed by the deposition of clay particles on the inner surfaces of the mold. The remaining slip is drained, and the cast is allowed to dry partially before the drain hole is plugged and the mold separated. The unfinished ware is given a final drying in an oven before it is fired into a finished product.
traditional ceramics Stages in the slip casting of a thin-walled whiteware container. Clay powder is mixed in water together with a dispersing agent, which keeps the clay particles suspended evenly throughout the clay-water slurry, or slip. The slip is poured into a plaster mold, where water is drawn out by capillary action and a cast is formed by the deposition of clay particles on the inner surfaces of the mold. The remaining slip is drained, and the cast is allowed to dry partially before the drain hole is plugged and the mold separated. The unfinished ware is given a final drying in an oven before it is fired into a finished product.

A tunnel kiln is the most efficient method for firing mass-produced traditional ceramics because it operates as a continuous process rather than a batch cycle.12

The system functions through the following mechanism:

  • Continuous Movement: Ceramic ware is loaded onto a conveyor belt or railcars that move slowly and steadily through a long, narrow chamber.13
  • Temperature Gradient: The kiln is designed with a specific thermal profile. As the ware traverses the tunnel, it gradually heats up from room temperature as it enters, reaches maximum heat in the central "hot zone," and then cools down gradually as it approaches the exit.12
  • Efficiency: Unlike intermittent kilns, which require cooling before they can be emptied and reloaded, tunnel kilns maintain a constant temperature in the center, significantly reducing fuel waste and labor.2

To ensure quality control during this traverse, pyrometric cones are often placed alongside the products to monitor that the ware reaches the required peak temperature.1