Jo Baer was a key figure among the celebrated protagonists of Minimalist painting in New York in the 1960s and first half of the '70s. It was during that period that she executed her series of different-sized squares as well as vertical and horizontal rectangles in the hard-edge style, works she later expanded into multipartite arrangements as diptychs and triptychs.
The most prominent feature of her paintings of that era is her composition of white or grey central areas encircled by a very thin band of colour which in turn is surrounded by a considerably thicker band of black. In these works it was important to not consider the black paint as a frame nor the white as the centre. Both white and black were the frames for the colour - black functioning to enclose it on one side and white on the other, white pushing colour far enough apart to work as it did. Baer used the perceptual principle of Mach Bands: while the eye sees a band of darkness within a black area and of lightness within the light area, the contrast is accentuated. The sharper the border between contrasting areas, the more pronounced are the bands (= the negative of the the second derivative, i.e. the rate of change of the rate of change). Mach Bands are perceptual illusions, but exact and measurable, objective ones.
Baer describes her early ambition to make "poetic objects that would be discrete yet coherent, legible yet dense, subtle yet clear." The artist produced what she called a radical redefinition of painting by arguing that the root of painting was neither flatness, nor colour, nor shape. She placed the emphasis entirely on light.
While other painters composed their paintings part by part, Baer created her paintings as units that had to be arranged in enormous calculable numbers of variation (factor x!) At the height of her fame Jo Baer turned away from Minimalism. In 1975 she left New York, went to Ireland, later to London and then to Amsterdam where she introduced images to her painting. In her well-known article "I am no longer an Abstract Artist" published in the magazine Art in America in 1983 she explained her new approach to "radical figuration" as a means of leaving the formal self-centredness of Minimal Art behind and granting the subject and its reality a place in the painterly illusion.