It describes more than 2000 trade names, chemicals, and materials that serve the primary function of lowering the overall cost of the end products to which they are added.
These ingredients are often selected based on secondary, property-enhancing functions. In the paper industry they are used to improve brightness, increase opacity, and reduce porosity. In paints, often referred to as inerts, extenders, and supplemental pigments, they are used to increase color, hiding power, weatherability and control viscosity. Fillers in plastics and polymers impart impact strength, lubricity, electrical and thermal properties. Diluents, besides supplying bulk to detergents, cosmetics, and pharmaceuticals, act to adjust dose or concentration.