On a building site in Switzerland, in the summer of 1955, a young engineer named Heinz Isler walked past a piece of wet burlap that had been draped over a mesh of steel reinforcement to keep it from drying in the sun. He stopped. He looked. He understood that if you took the shape the cloth had assumed under its own weight - a curve in pure tension - and inverted it, you would have a shape in pure compression. Cast that shape in concrete and you would have a shell that carried its own weight in pure compression, with almost no material at all.
From that morning Isler spent the rest of his working life building shells. Between 1954 and 2009 he designed and built more than fourteen hundred of them, which makes him, by the reckoning of the gta archive at ETH Zürich that now holds his models, the most prolific shell builder in the world. He found their shapes by hanging cloth, by inflating membranes, by freezing wet fabric outdoors in a Swiss winter and measuring what the ice had made. Physics as pencil.
Almost none of them were built for anyone famous. The shapes went up over petrol pumps, garden centres, tennis courts and factory floors, in a country that never made much noise about them. That is the Isler question, and it is the subject of this post: what happens when one of the most rigorous form-finding methods of the twentieth century is spent almost entirely on ordinary commercial buildings.
The man
Heinz Isler was born on 26 July 1926 in Zollikon, on the eastern shore of the Zürichsee. He studied civil engineering at the ETH Zürich and graduated in 1950.