In the late 1960s, Christensen, 64, found that the realism of his classical art training was restrictive and began using spray guns to paint colorful stacked loops on canvas, winning him critical acclaim, The New York Times said. Besides the process of painting and experimentation, he was concerned about how color interacted.
Christensen, who initially was inspired by Jackson Pollock, painted until his death. His works are featured in museums such as the Museum of Modern Art, the Fine Arts Museum of San Francisco and the Whitney Museum of American Art.
Christensen, who died Jan 20, is survived by his second wife, Elaine Grove; three sons, two sisters and one brother.