The nature of the medium determines the qualities and appearance of the paint.
Modern paints are more complex.
The media contain synthetic resins, of which a variety are now available. The development of water-soluble media gave rise to emulsion paints. Modern paints also contain extenders - salts, such as calcium and barium sulphate, which have little covering power but are used to supplement expensive pigments and to improve the brushability of the paint and the mechanical strength of the dried film. New solvent-free paints currently under development contain no hydrocarbons, which cause air pollution . Instead a free-flowing binder, such as Vernonia oil, is used.