As the quality and permanence of consumer and industrial products continue to improve, so do the demands on their appearance and durability. Therefore there is a steadily increasing requirement for more durable pigments to colour products such as paints, plastics, building materials and ceramics. As a consequence, the mixed metal oxides are of increasing importance to formulators.

These products can satisfy the most stringent requirements for heat stability and chemical inertness, as well as weather- and light-fastness, while taking account of the environmental requirements of the end product. To date, mixed metal oxides are the most stable pigments yet developed.

• Cobalt blue pigments with the spinel crystal structure vary from a reddish shade to a greenish shade as the trivalent cobalt content increases, this is accompanied by increasing strength : cobalt titanate greens have an inverse spinel structure.

  Use of these pigments eliminates warpage in polyolefins.

• Nickel and chromium titanates are based on the rutile structure of titanium dioxide. They offer high strength and hiding power, together with excellent light- and weather-fastness. They are available in a wide variety of shades and can be custom-formulated where the demand is sufficient.

  Use of these Heucodur pigments with organics gives improved light-fastness compared to mixtures using titanium dioxide.

• Iron chromite browns produce colours varying from a warm chocolate brown (HD 855) to a dark, blue shade (HD 869).

• The two blacks HD 920 and HD 940 are spinels which absorb visible light but reflect wavelengths in the near infrared. They are used in applications where heat buildup from absorbed sunlight or IR radiation needs to be prevented. The other blacks are based on copper and cobalt and absorb in the infrared.