Porcelain is a hard translucent material of which an important ingredient is china clay (kaolin), with various other materials added according to type, and fired to a high temperature in a potter's kiln. Most porcelain clock cases are of hard-paste porelain and are of French or German manufacture. The material is adaptable to the making of ornamental cases combining modelled figures, flowers or other decorative features, and it can be coloured by painting and firing enamels on its urface. Individual decorative figures, or sometimes complete cases, are made in biscuit (unglazed) porcelain, and such cases are normally protected from dirt by glass domes or shades. Porcelain, like all ceramic materials, shrinks and is inclined to distort during firing, and for this reason clock movements are fitted to porcelain cases with screws from loosely fitting rings at the back.