The Restoration of Siena's Duomo Window

Duomo, Siena Detail depicting Sant' Ansano in Duccio's Rose Window,1287-88 (following conservation 1996-2003)

Monumental stained glass, common in northern Europe, is exceedingly rare in Italy. A glowing exception is the glorious rose window showing the Virgin, saints and evangelists of the choir of Santa Maria Assunta, Siena's Duomo.

The window was commissioned by the Comune in 1287-88, but surviving documents do not name the artist. Only in 1946 did the art historian Enzo Carli prove convincingly that this was the work of Duccio di Buoninsegna, the outstanding Sienese painter of the era, and the Italian artist who most influenced the development of what came to be called the International Gothic style.

The deterioration of the leading supporting the window, which is 6 meters in diameter, has been a source of anxiety for some time. This summer the entire window was removed in a series of sections and taken across the piazza to Santa Maria della Scala, the medieval hospital complex that is presently being transformed into a cultural center, in order to undergo a painstaking conservation programme scheduled to last about three years.

Restoration generally has become a sensitive issue. The team cleaning the Sistine chapel ceiling almost certainly accidentally removed subsequent retouching by Michelangelo himself, and the restorer of Jacopo della Quercia's 'Monument of Ilaria Caretto' at the Duomo in Lucca unsuccessfully tried to sue the American art historian James Beck for declaring that afterwards the marble looked as though it had been scrubbed 'with Spic & Span and polished with Johnson's Wax' leaving the figure with the appearance of plastic - to cite but two of the most publicized recent cases.

Awareness that the eyes of the art world will be upon them has been one reason why chief restorer Camillo Tarozzi has installed a plate glass screen at the end of his workshop so that every stage of the operation can be monitored by the outside world. This arrangement will allow the Senese and visitors to see the restorers at work and the opportunity to compare 'before and after' sections of the window as the task progresses.

'Much of the leading is not original, dating back to previous restorations over the centuries, and is in very poor shape and will have to be replaced,' said Tarozzi. 'But nearly all the glass is authentic. The big challenge is the grisaille, the brownish paint the artist used to paint the facial details of the figures and so on.

'The grisaille would have been applied to the glass and then the pieces rebaked to fix it. Unfortunately, calculations of temperatures then were pretty hit and miss. Too high a heat would have cracked the glass, and so in some parts the fixing was more permanent than in others. Some of the missing grisaille is probably due to natural decay, but other parts have been rubbed off in the past by over-zealous cleaning.

'We are aware, above all, that we are dealing essentially with a painting, even if it is made of glass, and our whole approach to its conservation is conditioned by this,' said Tarozzi.

Echoing this theme, the director of the restoration, Dr Alessandro Bagnoli of the Province of Siena's Cultural Heritage Superintendency, said: 'Unlike many stained-glass windows in northern Europe, whose power often lies in the kaleidoscopic effect of their huge range of bright colors, an effect that is pursued even to the extent that the figures are not always immediately decipherable, the Siena window lets a lot of light into the building and strives to display with the greatest possible clarity the scenes it depicts.

'And the restricted use of colors - ruby red, purple, sky blue, yellow, emerald green - perfectly correspond to the palette Duccio used when painting his wood panels.'

Duccio, whose existence is first documented in 1278 and who died in 1318/19, was in many ways to the Sienese Renaissance what Giotto (his somewhat younger contemporary) was to that of Florence. The fact that Duccio is less of a household name is due not so much to his lesser skills and influence on his successors, as to the archrivalry of Siena and Florence (even if, despite being constantly at war with one another, artistically there was very considerable interchange between the cities.)

Early art historical writing was dominated by Florentines, and it is characteristic that Vasari should have attributed the famous Rucellai Madonna from the Santa Maria Novella in Florence (now in the Uffizi) to his fellow citizen Cimabue, while subsequent local luminaries detected the hand of a shadowy 'Master of the Rucellai Madonna', described initially as 'a follower of Duccio under the influence of Cimabue', then as 'a follower of Cimabue under the influence of Duccio', whereas there is now no doubt that the painting is actually by Duccio.

In 1308 Duccio was offered the unheard of sum of 3,000 gold florins to execute an extraordinarily complex, multi-panelled altarpiece for Siena's Duomo. It took him 32 months, and when it was carried in solemn procession accompanied by ringing church bells, drums and trumpets to the cathedral, it was described by a chronicler as 'the most beautiful picture ever made or seen.'

Unhappily, this masterpiece was dismantled in 1771 and though parts are in the Duomo's museum, other sections have been lost and others still scattered as far and wide as the National Galleries of London and Washington and the Frick Collection in New York. Consequently, Duccio's rose window is now his most important work remaining in the Duomo.

When restoration work is completed a special exhibition is to be organized to display the whole window before it is hoisted back into place again. This will not only be the last chance for a very long time to admire the work at close hand, but also the occasion for a timely reassessment of a great artist about whom there is still much left to learn.

First published: International Herald Tribune

© Roderick Conway Morris 1975-2023