Mangold’s early work consisted largely of monochromatic free-standing constructions displayed against the wall, such as "Grey Window Wall" (1964). In 1968 he began employing acrylic instead of oil paint, rolling rather than spraying it on Masonite or plywood grounds. Within the year, he moved from these more industrially oriented supports to canvas. In 1970 he began working with shaped canvases and within the year began brushing rather than spraying paint onto canvas. By the mid-1970s, Mangold moved on to overlapping shapes whose contours are formed by combinations of canvas edges and both drawn and implied lines. "A Rectangle and a Circle within a Square" from 1975, in the collection of the Honolulu Museum of Art is an example of these subtle geometric relationships.