What materials did M.C. Escher use on the eye 1946?

M.C. Escher's lithograph "Eye" (1946) was created using the lithography technique, which involves drawing on a flat stone or metal plate with a greasy medium. He primarily used ink and paper to produce the final prints. Escher's intricate designs and meticulous attention to detail are characteristic of his style, showcasing his ability to blend realism with abstract concepts.