During the years of the war, he struck up what was to be a lifelong friendship with Argentine artist Emilio Pettoruti, then a young man living in Italy and associated with the futurists. Also around that time, he began to pay more attention to painting, first with watercolor (which would always remain his main medium as a painter), although he gradually began working in tempera and – very occasionally — oils. He also adopted the pen-name of Xul Solar. His first major exhibition of his art was in 1920 in Milan, together with sculptor Arturo Martini.