Coming after the dominance of Abstract Expressionism during the immediate postwar era, by the 1960s artists sought to create a different kind of art that was not premised on self-expression or subjectivity. Described as Minimalists, many figures of this generation embraced an aesthetic of reduction as a way of countering painterly illusionism. Often this took the form of sculpture, as in the work of Donald Judd and Robert Morris, who strove to create geometric sculptures that referred to nothing outside of the objects themselves. Jo Baer addressed similar concerns on canvas and came to be recognized as among the most radical abstract painters of the time.
Horizontals Flanking, Large, Green Line (1966) is one of a group of paired canvases with similar visual elements that differ in color and orientation. Here, the title indicates two panels with a landscape orientation (thus “Horizontals”), which are hung next to one another (hence “Flanking”). The work features an expansive white field bounded on the edges by a black line and a green line. Baer built up the white ground with oil and acrylic to achieve a flat, even surface, and created the bands around the edges with oil paint using tapes and rulers, finishing them with a small brush by hand.
Baer was keenly interested in the optical processes of perception. In 1970, she published “Art and Vision: Mach Bands” in the multimedia arts magazine Aspen. The article uses scientific research to discuss the power of borders and contrast in visual perception, and urges artists to take advantage of the mechanics of vision. The term “Mach bands” specifically refers to the physicist Ernst Mach’s observation that where a dark field meets a light field, the viewer perceives the illusion of two bands—a light band in the dark field and a dark band in the light field. In Horizontals Flanking, Large, Green Line, the slim strip of green dividing the black band from the white field exaggerates this effect. Baer’s essay also discusses contrast enhancement, in which a color will appear brighter at its border if bounded by white or black—hence the intensity of the green in this case. Perceptual effects also contribute to the painting’s curious play between infinite space and finite space: if the viewer alternates his or her focus, the white ground shifts between appearing like unbounded space behind the painted frame or a concentrated field bounded by its border.
When the Guggenheim Museum acquired Baer’s painting in 1968, it was the first major purchase of her work by a museum. Similar work by Baer had been included in Lawrence Alloway’s landmark Systemic Painting show at the Guggenheim in 1966.