Saving the Frescoes of San Gimignano

From a distance, San Gimignano looks less like a town than a diagram of medieval ambition — a hilltop in Tuscany bristling with stone towers, fourteen of them still standing of the seventy-odd that once made the skyline a forest of competing egos. Tourists come for the towers, and for the postcard view, and increasingly for the gelato. Far fewer climb the steps of the Collegiata, the town’s great Romanesque church, and fewer still understand that the walls inside hold one of the most important and most endangered fresco cycles in Italy, and that keeping them on those walls has been the work of generations.

I went to San Gimignano to write about the towers and stayed for the frescoes, because the story of how a painting survives seven centuries on a damp stone wall is, it turns out, far stranger and more contested than the story of any tower.

What is on the walls

The Collegiata — properly the Collegiate Church of Santa Maria Assunta — is, from the outside, almost severe. Inside, it erupts. The side walls are covered, nearly floor to vault, in fresco cycles painted across the fourteenth century: scenes from the Old Testament along one wall, scenes from the life of Christ along the other, a vast and terrible Last Judgement at the entrance, and, in a side chapel, a celebrated cycle of the life of Saint Fina by Domenico Ghirlandaio. The names attached to the work include Bartolo di Fredi and Lippo Memmi, painters of the Sienese school whose luminous, narrative style fills the church with a sequence of images that functioned, for a largely illiterate congregation, as scripture made visible.

To stand in the nave is to be surrounded on every side by paint that is older than most nations. And that is precisely the problem the conservators have spent their careers confronting: paint that old, on walls that old, in a climate that swings between Tuscan summer heat and winter damp, does not want to stay where it is.

How a fresco dies

A fresco is not a painting hung on a wall; it is part of the wall. The technique — buon fresco — involves applying pigment to wet lime plaster so that, as the plaster dries, a chemical reaction binds the colour into the surface of the wall itself. This is what gives true fresco its extraordinary durability and its luminous, matte depth. It is also what makes it so vulnerable, because anything that attacks the wall attacks the painting.

The great enemy is water, and specifically salt. Moisture rising through the masonry, or seeping in through a failing roof, carries dissolved salts to the surface, where they crystallise as the water evaporates. The growing crystals lift the paint layer off the plaster from behind, a process conservators call detachment, and the surface begins to flake away in a fine powder. There is also the slower violence of light, of pollution, of earlier restorations applied with good intentions and the wrong chemistry — the nineteenth and early twentieth centuries are littered with frescoes “saved” by varnishes and overpainting that sealed in the damp and accelerated the decay.

The science of intervention

Modern fresco conservation, as practised at San Gimignano and codified in part by the great Italian restoration institutes, is governed by a principle that sounds simple and is anything but: do as little as possible, and make everything you do reversible. The era of confident repainting is over. Today’s conservator is closer to a surgeon than an artist, and the work proceeds at the pace of surgery.

A detaching fresco is consolidated by injecting fine lime-based grouts behind the paint layer to re-attach it to the wall — a slow, millimetre-by-millimetre process. Surfaces are cleaned not with solvents but increasingly with precisely calibrated tools: gels that lift grime without touching pigment, lasers tuned to vaporise a layer of dirt while leaving the paint beneath untouched. Where paint is genuinely lost, the modern ethic forbids inventing what was there. Instead conservators use techniques like tratteggio — fine vertical hatching in neutral tones that fills a loss at a distance but is plainly visible as restoration up close, so that no one mistakes the restorer’s hand for the master’s. The salts are tackled at the source, by controlling the building’s microclimate: managing humidity, repairing roofs and drainage, monitoring the walls with sensors that would have astonished the painters.

This is patient, invisible work, and it shares something with the disciplines this magazine returns to again and again — the reduction of the composer Arvo Pärt to the fewest possible notes, the refusal of the filmmaker Pedro Costa to cut away before a thing is fully seen. The conservator, too, succeeds by restraint. The best restoration is the one you cannot find.

The ethics and the politics

The reversibility principle is not a technicality; it is a confession of humility. It assumes that future conservators will know more than we do, will have better tools and better judgement, and that our job is therefore not to fix the fresco forever but to hand it on intact and unprejudiced to the people who come after. Every intervention is a loan against a future we cannot see.

But conservation is also, inescapably, politics and money. San Gimignano draws several million visitors a year, and those visitors are both the economic engine that funds the work and a source of the very damage it repairs — the heat and moisture of crowded bodies, the wear of footfall, the pressure to keep the church open and accessible against the conservator’s wish to close it and control its climate. The town that the UNESCO World Heritage listing was meant to protect is the same town whose protection depends on the tourism that listing encourages. Every World Heritage site in Italy lives inside this contradiction, and San Gimignano lives inside it more acutely than most, because its small medieval core cannot expand to absorb the numbers that come to admire it.

Going to see them

If you go — and you should — climb to the Collegiata di Santa Maria Assunta early, before the day-trippers arrive, when the church is quiet and the low light rakes across the walls. Buy the ticket that includes the Saint Fina chapel. Stand in the centre of the nave and let your eye travel up the cycles the way a fourteenth-century pilgrim’s would have, scene by scene, and try to hold in your mind the fact that almost every figure you are looking at has been, at some point in the last seventy years, lifted, cleaned, consolidated, or quietly held in place by a conservator whose name you will never learn.

That is the real subject of fresco restoration: not the painting alone, but the long, anonymous chain of hands that keeps the painting in the present tense. The painters of San Gimignano have been dead for seven hundred years. Their work is still wet enough, still alive enough, to be losing and recovering itself on the wall — and that it is still there at all is not an accident of survival but a continuous, deliberate act of care.

FAQ

Q: What makes the frescoes of San Gimignano important? A: The Collegiata di Santa Maria Assunta holds one of the most complete medieval fresco cycles in Tuscany — Old and New Testament scenes, a monumental Last Judgement, and Domenico Ghirlandaio’s celebrated chapel of Saint Fina — painted in the fourteenth and fifteenth centuries by masters of the Sienese and Florentine schools. Together they form a near-encyclopaedic record of late-medieval narrative painting, which is part of why San Gimignano is a UNESCO World Heritage site.

Q: Why are old frescoes so difficult to preserve? A: A fresco is bonded chemically into the plaster of the wall itself, so any damage to the wall damages the painting. The main threat is moisture carrying dissolved salts, which crystallise near the surface and lift the paint layer off the plaster, causing it to flake away. Light, pollution, crowds, and poorly chosen past restorations all accelerate the decay.

Q: What techniques do conservators use today? A: Modern fresco conservation follows two governing principles: minimal intervention and full reversibility. Conservators re-attach lifting paint with lime-based grouts, clean surfaces with gels or precisely tuned lasers rather than harsh solvents, and fill losses with visible techniques like tratteggio hatching so restoration is never confused with original work. They also control the building’s humidity and repair its structure to stop damage at the source.

Q: Can visitors see the frescoes, and how should they plan a visit? A: Yes — the Collegiata is open to visitors, with a combined ticket that includes the Saint Fina chapel. Arriving early in the day, before the heaviest tourist crowds, gives the best light and the quietest conditions. Visitor numbers are carefully managed because crowds raise the humidity and heat that threaten the paintings.