Twentieth-Century Painting and Sculpture in the Philadelphia Museum of Art
Ellsworth Kelly's decisive transformation of line, shape, and color into works that occupy the territory shared by painting, sculpture, and architecture is powerfully evident in Diagonal with Curve III, one of a series of five monochrome paintings that explores the tension between straight lines and curves. Kelly has remarked that the experience of seeing a small group of Juan Gris's paintings at the Philadelphia Museum of Art in the 1950s first led him to conceive of paintings in series that could be thought of as a related whole, especially when exhibited together. His exploration of the expressive potential of simple curved lines and shapes derives from the same period, specifically from his 1952 proposal for a book to be called "Line Form and Plane," which included an elegant linear drawing of a curve isolated against a stark ground.
In making a canvas curve, Kelly defied the orthogonal organization of parallel lines and planes that has for centuries been the framework for painting. He undid many assumptions about the physical reality, conceptual boundaries, and function of pictures on walls. Taking abstraction to a level of simplicity that would have been unthinkable to Constantin Brancusi or Jean Arp—early modern artists from whom Kelly took inspiration—Diagonal with Curve III unsettles definitions of what is painting and what is architecture, as well as what is figure and what is ground. The two parallel edges at the right and left of the canvas establish a contrast with the differently bowed longer sides of the work, with their edges meeting at masterfully orchestrated angles. Using remarkably restricted means, Kelly drew with color and edge—an approach that evokes Henri Matisse's cut-outs—to charge the black matte painted surface with an electrifying energy and to create a soaring, monumental presence. Twentieth Century Painting and Sculpture in the Philadelphia Museum of Art (2000), p. 130.