Arnold earned bachelor's and master's degrees in art at Oberlin. He later earned a master's of fine art at the University of Minnesota.
He taught in Oberlin in 1941, joined the Army the next year and spent 1944 to 1946 in China with the Office of Strategic Services. He became a captain and earned a Bronze Star. Back at Oberlin, Arnold was asked to teach printmaking and became a leader in the field. He studied woodblock technique in Japan with the famed Toshi Yoshida. He tried to combine shapes and colors in what he called a "lively, yet disciplined, unity."
