A recent discovery for artists, these paints depend on acrylic resins only produced commercially since the 1930s. Methyl methacrylate in mineral spirits forms a pigment medium, directly applied or thinned with turpentine. Polymerized, it produces a milky emulsion used in polymer colours, which are thinned with water, drying quickly to an insoluble finish, and colour of great brilliance. Both types have become popular; David Hockney is one artist who has effectively exploited their special qualities.