Have Italy's art restorers cleaned up their act?

Piero della Francesca's masterpiece, The Legend of the True Cross, has re-emerged after more than a decade under wraps. So has Italy managed to restore faith in its conservation policy after the uproar over the cleaning of the Sistine Chapel?

They say that if all the economists in the world were laid end to end, they would fail to reach a conclusion; and much the same is true of specialists discussing the way to restore frescoes. While economists look into the future to anticipate the unpredictable, art restorers do battle with the past, laboriously attempting to return the work of art to its original purity and freshness. But to do so without damage or even destruction is no easy task, and debates over how best to proceed are often long and bitter.

They say that if all the economists in the world were laid end to end, they would fail to reach a conclusion; and much the same is true of specialists discussing the way to restore frescoes. While economists look into the future to anticipate the unpredictable, art restorers do battle with the past, laboriously attempting to return the work of art to its original purity and freshness. But to do so without damage or even destruction is no easy task, and debates over how best to proceed are often long and bitter.

Over the last 30 years, the Italian government, with the help of private sponsors, has undertaken a programme of radical cleaning and restoration of some of the most famous frescoes of the Renaissance. Apart from carrying out the essential work of cleaning, repairing structural damage, and protecting the frescoes from damp, restorers have also used the latest technology to try to determine the exact nature of the original painting; and have used that analysis to offer a definitive image of the work for future generations.

This is a more controversial process than it might appear to be at first sight. It is one thing to perform Bach's music on period instruments and to record the performance on CD (thereby producing a sound that is both technically pure and historically authentic); unfortunately it is simply not possible to do something similar with works of art that have been continually modified by history ever since they were created.

Take, for example, Piero della Francesca's Madonna del Parto, one of the most sublimely mysterious works of the Renaissance. At some point in the past the fresco was damaged, and the top quarter (containing the top of the tent which frames the Madonna, a simple but essential element of the overall composition) was repainted. As part of the "restoration" this portion was removed, and is now placed alongside the rest of the work. As a result the integrity of the original is respected, but part of the painting's meaning is needlessly lost.

Even when frescoes have not been altered or damaged in any way, it is often hard to be sure that cleaning does not also remove part of the painting.

In theory, all fresco painting was done while the plaster was wet: a composition was divided into giornate, each of which corresponded to the area that could be covered in one day; plaster was then applied to that section, and painting began; as the plaster dried the paint was sealed into the wall, and could not be reworked. It was a very demanding technique, which left no room for errors and gave the painter little time in which to build up modelling, or to explore the more complex aspects of his art. Small wonder, therefore, that artists were tempted to add to the painting once the plaster was dry - and that part of the work, being neither protected by varnish nor sealed into the wall, is clearly vulnerable to cleaning abrasives.

There seems little doubt that the ceiling of the Sistine Chapel was in part painted a secco (that is, once the plaster was dry), but the restorers none the less decided that radical cleaning was necessary, given the amount of dirt that had accumulated (in particular from candle smoke). As a result the ceiling now has a curiously washed-out look, with pretty but flavourless colouring - an effect quite unlike that of Michelangelo's intensely sensual sculpture.

The debate over the Sistine Chapel restorations was particularly acrimonious; at the same time an argument dragged on concerning another work of equal importance to the Italians, Leonardo's Last Supper. Here the problems were largely of the artist's own making: Leonardo chose to work with oil as the medium for pigment (rather than tempera, egg yolk and water, as was usual for frescoes), and the experiment proved disastrous: the painting soon began to deteriorate and required re-painting and repair at regular intervals over the centuries.

All this over-painting was removed during the Eighties. Once done, it became clear that little of the original remained intact; so the restorers got out their watercolours, and not only filled in the gaps but also filled out the meagre remains of Leonardo's painting. The result is more of a fiasco than a fresco (Christ's head, which Vasari tells us was left deliberately unfinished, now looks as though it was painted by a rather uninspired art student) - but no matter, the world has a painting which it can think of as Leonardo's, and the sponsors get a return on their investment.

Luckily not all operations have been so controversial. Signorelli's Last Judgement at Orvieto Cathedral, which was restored to public view a few years ago, met with universal approval, while the re-opening of Piero della Francesca's frescoes of The Legend of the True Cross at Arezzo in April this year surpassed all expectations.

At a technical level the situation here was extremely complex and difficult to resolve, yet the restorers have succeeded magnificently in giving the work a new lease of life, while respecting the integrity of the original: for example, small gaps in the fresco have been filled in with watercolour, but no paint has been added to the work itself. Thus the composition has a unity which it lacked before the restoration, while the freshness and luminosity of the colouring enables the spectator to respond to the work as if it had been finished yesterday.

Such a spectacular effect says as much about the painter as it does about the skills of the restorers: like Masaccio and Filippo Lippi, whose frescoes in the Cappella Brancacci in Florence have been so beautifully restored, Piero understood and mastered completely the art of fresco painting. Leonardo, on the other hand, made a mess (technically speaking) of his commission, while Michelangelo was a sculptor who looked down on painting and never wanted to paint the Sistine Chapel. In the final analysis, the restored work of art can never be better than the original work allows it to be.

Renaissance frescoes were designed as public works of art (their prime function was to recount stories and events from the Bible to a largely illiterate population), and it has never been easy to protect them from natural or man-made disasters. Leonardo's Last Supper, for example, was vandalised by Napoleon's soldiers, and bombed during the Second World War, while an earthquake almost destroyed the Madonna del Parto in 1917. And who knows what the future will bring? Just three years ago an earthquake damaged Giotto's frescoes at Assisi; repair work is now in full swing...

However sophisticated the technology used, fresco restoration can never pretend to be definitive nor faultless. The work just completed at Arezzo shows the very best that can be done; and it seems fitting that Piero, who was a profoundly religious man, and whose extraordinary Resurrection can be seen at Sansepolcro, should now, thanks to 15 years of hard work, find his own masterpiece resurrected, reborn.

'The Legend of the True Cross', restored by the Banca Popolare dell'Etruria e del Lazio, is in the Basilica di San Francesco, Arezzo and is open Mon-Fri 9-7. Sat, 9-6.15; Sundays and holidays, 1-6. Visits are twice hourly, last 25 minutes and must be booked in advance by phone, at 06-32810, or 0575-900404, daily 9-9; or bought at the church. All the other frescoes referred to in this article are open to the public. Opening times vary