In 1947, Ib Geertsen co-founded the exhibition association Linien II, which in the following years became the focal point for concrete art and its practitioners in Denmark. He participated in the group's first exhibition in 1947 and continued until 1951. Geertsen's art underwent great development through the 1950s. The circle and teardrop form emerged as recurring themes in flat, cosmos-like compositions, where the shapes revolve around each other. At the beginning of the 50s, Geertsen's self-proclaimed work with the “contrasting relationship between curved and straight lines” was intensified. Most iconic is the “drop” shape, which Geertsen repeatedly emphasized had nothing to do with a drop in its natural form. In the early works, the drop appears in several different, often slightly crooked versions, but is sharpened into an almost form-like signature. A signature that takes on a new kinetic dimension and spatiality in Ib Geertsen's sculptural works, including the mobiles. With these, Geertsen reached even further in his efforts to fulfill one of the basic objectives of constructivism and concrete art; to break the boundaries between painting, architecture and interior design.