<Li> Drying wood for use as firewood </Li> <Li> Heating wood to the point of pyrolysis to produce charcoal </Li> <P> Kilns are an essential part of the manufacture of all 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 electrical control systems to firing regime, although pyrometric devices are often also used . </P> <P> 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 predominantly consists of silicon and aluminium oxides . </P>

Kiln-fired clay works of sculpture or pottery are called