Chamberlain's work achieved critical acclaim in the early 1960s, gaining him a reputation as a three-dimensional Abstract Expressionist. His sculpture was included in The Art of Assemblage at the Museum of Modern Art, New York, in 1961, the same year he participated in the São Paulo Biennial. From 1962, Chamberlain showed frequently at the Leo Castelli Gallery, New York, and in 1964 his work was exhibited at the Venice Biennale. While he continued to make sculpture from auto parts, Chamberlain also experimented with other materials. From 1963 to 1965, he made geometric paintings with sprayed automobile paint. In 1966, the same year he received the first of two fellowships from the John Simon Guggenheim Memorial Foundation, he began a series of sculptures with urethane foam, which he rolled, folded, cut, and tied. He then applied methods of crushing and compression to galvanized steel and paper bags. These were followed in 1970 by sculptures of heat-crumpled Plexiglas. During this period he also made the film The Secret Life of Hernando Cortez (1968), starring Andy Warhol's superstars Taylor Mead and Ultra Violet. Chamberlain's work was presented in a retrospective at the Guggenheim Museum, New York, in 1971. Small examples of his newest engagement with aluminum foil were exhibited for the first time.