During World War I, Arp made the first works with curvilinear shapes. Around 1917 he began creating wood reliefs made of flat, irregular pieces of wood, which he mounted on top and next to each other. Arp used these works to explore abstract biomorphic art inspired by, but not imitating, nature.
He began creating three-dimensional standing sculpture in the mid-1920s, but also continued making reliefs, some of which he also had cast in bronze. Towards the end of the 1920s he first created many of his works in plaster himself, whereas the earlier works made of wood had been made by a carpenter. He either built up the form or he would work on a piece of plaster he already had in the studio. This was a meditative work for him, rasping and sanding away the plaster until the piece took on the shape he intended it to have.
