The carrier evaporates as the paint dries, leaving the solids behind as a thin surface film that clings to the underlying surface. Both alkyd and latex paints were developed in the 1940s. Latex paints use vinyl binders and a water carrier. Originally latex paints were less durable and did not adhere well. Subsequent improvements, specifically the introduction of acrylic and urethane binders, have improved quality.
Alkyd paint forms an impermeable film through constant surface oxidation.
This process, which goes on for the life of the paint, causes alkyd films to lose their color and become brittle. Acrylic particles draw together as the water evaporates, forming a stable yet flexible film that expands and contracts with the underlying surface. As a result, acrylic paints hold their color longer than alkyds and are less susceptible to cracking. The ingredients of a paint are suspended or dissolved in a base that is either oil or water. New clean-air laws mandate that the amount of volatile organic compounds in paint be lowered.