Peter Voulkos, one of the most influential ceramists of the twentieth century, rejected the limitations of traditional pottery in favor of an expressive, nonfunctional art form, ushering in a “clay revolution” in American ceramics. Among his most innovative forms are the “stack” vessels, towering assemblages of wheel-thrown clay rings heaped into upright, chimney-like forms that recall the wood-burning kilns they were produced in. Drawing on the action paintings of the Abstract Expressionists he admired, Voulkos aggressively manipulated the surfaces of his pieces, often slicing and puncturing them with a knife.