Rothko called his paintings from 1948 to 1949 "multiforms" because of the proliferation of patches of color, By 1949–50, he had replaced the multiple areas of color and intimate scale with large horizontal expanses of bounded color on mural-sized canvases.
In No. 13, Rothko used thin sponges, rags, and cloth to build up veils of color. The layers of paint have bled into their support, all but eliminating surface texture and evidence of the artist's gesture. Hazy blocks of color dispersed throughout the painting are activated by intermittent opaque strokes of purple and red paint. The soft, uneven segments seem to float on the support. Rothko eliminated perspectival illusionism, but the relationships of color create a sense of depth in the flat composition. The solid orange block at the lower left, for example, pushes forward, while the neighboring purple pulls back. Using abstract form to make an immediate and, to his mind, universal artistic statement, Rothko's simplified visual vocabulary was intended to evoke elemental human emotions and to prompt contemplation.
Text by Phoebe Wolfskill, from Krannert Art Museum: Selected Works, 2008