Rising to prominence in the 1960s and 1970s, process art incorporated the act of making as a vital part of the final work of art. The Abstract Expressionist movement served as an important antecedent for process artists—the paintings of Jackson Pollock, a leader of that movement, made the very act of painting and the movements of the artist visible on their surfaces. Indeed, the energetic action of Pollock’s painting could be said to be the subject of his abstract drip paintings. Process artists, including Robert Morris, Lynda Benglis, and Eva Hesse, gave precedence to the means by which art was made, and the properties of the materials they selected. Morris allowed the force of gravity to shape his large works made of cut industrial felt. Benglis created a series of “pour pieces,” in which she poured brightly colored liquid latex on the floor. The material took on the shape of the space around it, serving as a document of the performative act of the work being made. The organic, random forms served as a rebuttal to the rigidity of Minimalism. Hesse experimented with unconventional materials like fiberglass, wax, and rubber, embracing the innate, sometimes unstable, properties of these substances. Other artists associated with the Process Art movement include Richard Serra, Bruce Nauman, Robert Smithson, and Keith Sonnier.