Alkyd resin, a complex oil-modified polyester that serves as the film-forming agent in some paints and clear coatings. Developed in the 1920s, alkyd-based enamel p aints were once one of the most important types of surface coating. Owing to their incorporation of volatile organic solvents and to their low durability on exterior surfaces, they have yielded preeminence to newer polymer systems (particularly water-based latex paints). Nevertheless, alkyds are still used in low-performance industrial coatings and in interior paints.