Reinforced concrete shells frequently constitute the most visible element of a building envelope. They dominate the architectural expression, yet the three-dimensional form is generally determined by the engineer according to its structural efficiency, rather than by the architect according to aesthetical considerations. This raises the question “Who is the author of the design?” The design philosophy of recognised shell designers is introduced, specifically that of Swiss shell designer and “structural artist” Heinz Isler, who is considered to have had particular sensitivity to the aesthetics of his shells, rooted in his admiration of the natural world and derived by natural laws. The Sicli Factory shell, 1968, is taken as a case study and is used to compare Isler’s design method with contemporary digital form-finding using the particle spring method. It is concluded that there are advantages and disadvantages to both physical and digital modelling methods. Designers should be encouraged to explore with various approaches.