Coating improves the opacity, lightness, surface smoothness, lustre and colour-absorption ability of paper. It meets exacting quality demands regarding surface smoothness. Coating means that a layer is applied to the paper, either directly in the papermaking machine or separately. Varieties of coated paper range from pigmented to cast-coated. The coat consists of a mix of pigments, extenders such as china clay and chalk, and binders such as starch or latex. In addition, various chemicals are added to give the paper the desired characteristics.