A private collection of around 20 works is going on sale as part of Ketterer’s two-day jubilee auction on 6 and 7 June, celebrating the firm’s 60th anniversary. All proceeds from this part of the auction will go to a foundation that supports molecular-biological research at the American Mayo Clinic. A highlight of the private collection is Alexander Calder’s Yellow Crinkly, 1963, an eye-catching standing mobile made of steel sheets and wire, estimated at €300,000 to €400,000. The American-born sculptor invented motor-driven “mobiles”, a term coined by Duchamp, and unmotorised “stabiles”, conceived by Arp, which Calder later combined to create his “standing mobiles”. The kinetic sculpture’s colourful, hovering forms balance on a firm stand providing an ever-changing abstract composition, which is never out of balance. Through integrating form, motion and colour, Calder created some of his most sought-after works. Peggy Guggenheim was an enthusiastic follower, as was the international art market.