Christian Bolt won't stop until he can revive the Renaissance sculpture technique of terra secca

A torso 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 Christian 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 Christian, 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 Christian, 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 re-create terra secca, a project that will run for the next three years. In a way, this, too, marks a return to the Renaissance, when artists and scientists worked closely together or were, in the case of Leonardo da Vinci, one and the same: ‘I personally believe there is great potential in this collaboration.’ Scientific analysis, explains Christian, can identify the individual components of terra secca, but not the process with which it was made, so he has been ‘cooking up’ different recipes from a small selection of ingredients: natural clays from the Graubünden region, a pinch of river sand, a dollop of marble powder, a handful of ground bricks. Complicating the issue is that terra secca changes over time. ‘The scientists told me we need to wait at least a half a year to see the final result of each recipe.’

It has been a rollercoaster of high thrills and abject failures: ‘When I came home after discovering terra secca in Florence, I immediately wanted to find out: “Christian, is this possible or do you need to forget it?” I tried to form a little figure, but I needed to find another way of doing the armature, because you cannot use iron or wood.’ Inspiration struck and he turned to tow: ‘It worked so well,’ he exclaims — only for the finished statue to become about one-third smaller than he had anticipated. ‘Even if it shrank, I’m very proud of it.’

He has since worked out, with help from ETH researchers, that he can cut up the tow into small pieces, which he mixes with clay to form the armature, but is now facing a fresh challenge. ‘It makes cracks,’ he says of the latest recipe he has tried, which includes burnt limestone as a binder. ‘When humidity comes out, it shrinks: we need to find out how to stabilise the material, so that it will remain the same volume.’

True to Galileo’s scientific method, he tested the formula with a small amount of limestone and again with a much larger quantity — ‘and what was really frustrating is that I got the same result — always the cracks. Maybe I used the limestone too hot, maybe I used it too cold, maybe I’ve added too much water. Nobody knows’. His next step is enlisting the help of some limestone specialists to see whether they can help him figure out what might be going wrong.

Even when things go pear shaped, Christian never loses the sense of excitement that comes from making new discoveries. His eyes dance and he can’t contain his smile when he says: ‘This is something no professor has ever taught me. This is something I need to do by myself, with all the trials and successes — it becomes very personal.’ An artist used to working with bronze, wood or marble (two examples of the latter are in Sir Elton John’s collection), he is also intrigued to see how his own style will evolve in response to terra secca: ‘If the material changes, your artistic language will do so, too, because the working process is different.’

For example, he explains, modelling terra secca takes much longer than standard clay. ‘With this technique, you do some work, then you need to let it dry a little bit before you can continue — it goes on for weeks, but this allows you to use different tools, which you could not have used on wet regular clay.’ He has only completed half a dozen terra-secca pieces to date, but, he says, ‘there is an art historian who knows me very well and he told me: “I could already tell the change in your way of modelling”’. The terra-secca work will be on show, together with the raw clay used to make it, in his atelier, where he’s also hosting an exhibition of paintings by Swiss artist Patrick Devonas during Klosters Music 2025, the village’s annual classical-concert festival.

Christian’s ultimate ambition is to create a life-size terra-secca statue, as well as reliefs: ‘It will take time to get to this point, but, yes, I’m very positive.’ For him, however, the project is more than ‘just’ finding a great new material. Fittingly for a man who works in the mountains — his old studio, which he has now outgrown, is a converted Alpine barn in a glade dotted with flower-embroidered chalets and fringed by forbidding peaks — this is also about the environmental crisis we face and how we approach it.

‘I was at [Europe’s] biggest open-air sculpture exhibition, the Triennale in Bad Ragatz, and more than 50% of the statues were made of plastic. I thought: “This is not possible. This is not the culture I would like to support.”’ He notes that, when artists do engage with ecological issues, it is often to raise alarm, which is of course important, but can also be demoralising.

Instead, he wants to give people hope: ‘If the recipes for terra secca work out well, the good thing is that, in time, the pieces we make with it will improve. And this message, I think, is philosophically and intellectually vital. Through culture and art, we can create a new world that will be better than today.’

Klosters Music takes place in Klosters, Switzerland, from July 26–August 3

This article originally appeared in the July 16 issue of Country Life.