In the early 1970s, Serra’s drawings primarily involved a number of traditional mediums such as charcoal, ink, and lithographic crayon on paper—to the mid-1970s when he turned to black paintstick, a crayon comprised of a mixture of pigment, oil, and wax. He has since used paintstick or oilstick extensively in its various forms, making heavily textured gestural drawings, often creating large-scale thick black surfaces highlighting his interest in process and weight. Serra sees black as not a color, but rather, a material that has weight and responds to the laws of gravity.