Abstract Expressionism of the 1940s and 50s was gestural—muscular brushwork on primed canvases. In the 1960s, however, a movement of avant-garde painters changed everything by questioning the practice of seeing ground and figure as separate. They soaked, poured and spattered unprimed canvases. Color took on the control that formerly belonged to the brush. In an exhibition that examines the various styles within this movement, works by Morris Louis, Kenneth Noland, Jules Olitski, and Helen Frankenthaler are on display. —E.C.