Minimalism is a term that describes simple, geometric art that is often impersonal and made with a new set of materials, including aluminum, Plexiglas, plywood, and steel. Minimalist artists attempted to distill their work into a pure form, editing any reference to personality, feelings, symbolism, or story. The style became popular during the mid-1960s, though many art critics at the time accused minimalism of being too cold, and questioned whether art could, or should, be produced by industrial means. The term “minimalism” has been used to describe the art of many artists, from Ad Reinhardt to Yves Klein, Frank Stella to Robert Rauschenberg. The work of artist Donald Judd (1928–1994) is a good example of minimalism. Judd explored the difference between painting and sculpture with his series of wall structures. Judd’s wall structures are composed of a series of machine-made rectangular forms that protrude from the wall, forms that he called “specific objects.” The work of artist Anne Truitt (1921–2004) occasionally blurred the line between minimalism and color-field painting; however, her minimalist sculpture Grant (1963)—a long wooden beam, painted in acrylic—was a pure, impersonal, geometric form.