A bright white, insoluble powder (chemical formula TiO2) added to paper pulp as a filler or applied as a coating pigment, and is the most efficient means of increasing paper brightness and opacity. Of the three primary optical brighteners, it is more effective than clay, or calcium carbonate, but is also the most expensive. Titanium dioxide is an oxide of the metal titanium, and is used widely in the manufacture of other materials, such as plastics, leathers, face powders, linoleum, and paints. (See also Fillers.)
Titanium dioxide is also used as a white pigment in printing inks, and has the highest degree of opacity of any white pigment. It accounts for 80% of all the white pigments in use. It is extremely fast-to-light, and resistant to nearly all substances. There are two major grades of titanium dioxide: anatase (bluer, harder, and more opaque) and rutile (less opaque and softer). Various coatings of aluminum, silicon, or zinc oxides can also be added to obtain a variety of desired properties. Titanium dioxide is used in every type of printing ink manufactured. When used in printing ink, titanium dioxide is also called cover white. (See also White Pigments.)
('CI Pigment White 6 No. 77891'.)