A significant figure in the development of color field painting, Helen Frankenthaler was best known for her innovative staining technique, which initially involved pouring turpentine-thinned oil paint onto unprimed canvas. In 1963 Frankenthaler started working with acrylic paint—which didn’t leave residual, halo-like marks of oil—using it to flood the surface rather than stain it.

The result is evident in Red Frame, a Sheldon treasure. Blue, green, and yellow forms are surrounded by the eponymous red frame, which functions to reinforce both the shape of the canvas and its status as an object on the wall.