In the footsteps of Michelangelo

At his studio fringed by the mountains of Klosters, Swiss sculptor Christian Bolt is feverishly cooking up recipes to re-create terra secca, a material used in Renaissance Italy, not only to expand his own artistic horizons, but to help save the planet

- Carla Passino

ATORSO by Michelangelo baffled Swiss sculptor Christian Bolt. He had stumbled upon it at the Accademia delle Arti del Disegno in Florence, Italy, where he is a professor. The institution, which protects the cultural inheritance of the Italian Renaissance, was looking after the maquette for an aristocratic Florentine family and Prof Bolt was mesmerised by the material of which it was made: ‘This was not terracotta, marble or bronze—this was something beyond,’ he recalls. That's how he discovered terra secca, ‘a very old technique from the Renaissance’. His interest piqued, he toured Florentine museums and found, at the Bargello, several terra-secca maquettes by Giambologna, as well as Michelangelo: ‘I [became] very, very fascinated by the expression and the language that comes forth through this material.’

Where better-known terracotta is made by firing clay, terra secca is air dried and held together with natural bindings. It had been widely used in 16th-century Italy, particularly for bozzetti (maquettes), although, says Prof Bolt, Giambologna combined it with stone when he was sculpting his 36ft-high Apennine colossus. As artists progressively embraced terracotta and other materials, however, knowledge of how to make terra secca became lost. This prompted Prof Bolt, who is based in Klosters, in the Swiss canton of Graubünden, to get in touch with ETH Zurich, a university that specialises in science, technology and engineering—and, much to his surprise, he learnt that some scientists there were also looking to revive a similar material: ‘They are researching alternatives to concrete, because it’s not sustainable, so they're very, very interested in Roman cement [a concrete mix that sometimes included volcanic ash].’

He has since joined forces with ETH to try to recreate