Group of American painters based in Washington, DC, who from the mid-1950s responded to Abstract Expressionism by producing non-gestural, totally abstract canvases that stressed the optical effects created by the interrelationships of various colours. Named retrospectively in a survey exhibition held in 1965, they worked in a number of different styles including those loosely referred to as Post-Pinterly Abstraction, Hard-Edge Painting, and Colour Field Painting, but all used acrylic paints. One of the most influential of the painters, Morris Louis, moved in 1952 from his native Baltimore to Washington, DC, where he met several like-minded artists at the Washington Workshop for the Arts, founded by local painter Leon Berkowitz (1915–87). Following the example of Helen Frankenthaler, Louis began in the early 1950s to pour extremely thin acrylic paints directly on to unprimed canvases to produce ‘stains’ of overlapping, translucent colours. The work of most of his colleagues, however, and particularly that of Kenneth Noland, was characterized by hard-edged, geometric abstract forms and especially by repeating patterns, such as concentric circles and chevrons, from which Noland produced series of works. The third principal group member was Gene Davis (1920–85), a native of Washington, who began painting in 1958 and quickly developed his signature approach of narrow, vertical stripes of colour that covered the entire canvas surface from edge to edge.