Some of the ribbons and bars so rhythmically meshed in Number 20 are recognizable as letters of the alphabet (E, X, or Z), but these and their more abstract neighbors evoke calligraphy without constituting it. Like the circles and crosses in the painting, they can be traced to the Surrealist interest in universal images—immediately legible images that nevertheless escape facile interpretation by the conscious mind. Tomlin had made repeated visits to the exhibition Fantastic Art Dada Surrealism at The Museum of Modern Art in 1936-37, and he shared the wide interest in Surrealism among the artists of the New York School. (This interest was encouraged when World War II drove a number of European Surrealist artists to emigrate to New York.)
His work of the 1930s, however, had been Cubist in inspiration, and the background of shifting rectangles in Number 20 ultimately derives from the structural grid of Cubism; the work's limited color range also recalls the reduced palette of Cubist paintings of 1911-12. The result is a painting that combines decorative elegance with an austere sobriety of spirit.
from The Museum of Modern Art, MoMA Highlights, New York: The Museum of Modern Art, revised 2004, originally published 1999, p. 201