The process of heating a ceramic body in a kiln to harden it, fuse the components, and to melt the applied glaze so that it vitrifies to the surface. It can take several firings at different temperatures to complete the process. An initial biscuit firing transforms the clay mixture to a hard object, both physically and chemically. The temperature varies depending on the type of clay or paste: 700–1200 degrees celsius for earthenware, 1200–1350 degrees celsius for stoneware, and 1250–1450 degrees celsius for porcelain. A further glost firing fuses the glaze to the body. Enamel colours, used to decorate the body over the glaze, are then applied and the piece is fired again at a lower temperature in a muffle kiln, usually between 700 and 900 degrees celsius. A final firing takes place, at a lower temperature still, if gilding is required.