It is not uncommon that an illustrator is excellent at black and white OR colour, but not both to the same extent. Oscar Cahén, however, showed equal proficiency at both. His technique varied from tightly rendered to loosely scrawled, in pen or with brush. Sometimes he used a scratchy tool, perhaps a bamboo pen, for a more textured line. Other times, a thick crayon was applied to rough paper for a grainy look.