His father was a barber. He studied at the Royal Academy in Amsterdam in 1940-43. Appel sought to develop an impulsive formal language based on life, in reaction to geometric academicism. He even founded with others an experimental group. In Paris in 1949, he focused on mastering creative power and did canvases that "look like they were done in a rage". An action painter, Appel gives full rein to his violent expressionism in numerous mural compositions and in stained glass windows.