The Screwarch Bridge etchings are among the most important in Oldenburg's oeuvre. They not only document a proposed bridge in the form of two arched screws designed to span a river in Rotterdam, but also the artist's experimentation with, and mastery of, etching. The series begins with State I, which serves as a blueprint for the bridge. Oldenburg achieved this precise model by using a needle to cut around cardboard templates directly through a hard ground applied to a copper plate. With State II, the artist begins to add subtle details to the bridge by using aquatint plates in varying shades of grey, and introducing the river, landscape and sky. For State III, his fully realized vision, Oldenburg used the same plates from State II, now inked in color. Before the printing of each impression he added hand-painted details directly onto the plates for the trees, cars, boats and landscape. As a result, each of the 25 impressions have unique features and subtly varying imagery.