Herk Van Tongeren based his sculpture on history, philosophy, and other cultures. Once he had mastered the techniques of working with traditional bronze, he experimented with more modern materials like steel I‑beams, wooden boxes, and found objects. In the 1970s he took everyday objects and juxtaposed them with words to create nonsensical collages. Later, Van Tongeren returned to bronze, because he liked the tension between this classical medium and his modern style. He had a lifelong interest in metaphysics and alchemy and in 1979 began his Serie Metafisica. These bronze sculptures grew out of the surreal works of Giorgio de Chirico and Alberto Giacometti.