Ceramic Tunnel Kiln
Kilns are an essential part of the manufacture of all ceramics, which require heat treatment, often at high temperatures. During this process, chemical and physical reactions occur that 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, by the temperature at which it is fired, and by the glazes that may be used. Although modern kilns often have sophisticated electrical systems to control the firing temperatures, pyrometric devices are also frequently 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. Part of 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. This crystalline material is predominantly silicon and aluminium oxides, and is very hard and strong.