UNTIL recently the city of Florence could still be enjoyed as one of the western world's greatest open-air sculpture collections. Here, accessibly and free of charge, one could see the masterpieces of Ghiberti, Donatello, Cellini and Giambologna in the spaces and monumental settings which gave them civic meaning and political resonance.

This outdoor gallery is gradually being emptied of original works. Tourists are harangued by their guides in front of a gleaming replica of Ghiberti's Gates of Paradise; a modern cast of Donatello's Judith stares balefully down from her plinth. Most confusing of all is the present state of the church of Orsanmichele - the monument whose transformation from granary to oratory to Gesamtkunstwerk epitomises the flowering of corporate patronage in early renaissance Florence (see p.812). Here many of the external niches stand empty, and Donatello's St Mark has been replaced by a reproduction in artificial stone.

At first sight disconcerting, these developments signal a welcome decision on the part of the authorities to face up to the degeneration of outdoor sculpture exposed to atmos- pheric pollution - a degeneration pointed out in the strongest terms in these pages fifteen years ago.' Nonetheless they have aroused controversy, and the issues they raise are of general importance. Should sculptures be wrested from their context? Should they be replaced with copies? Where and how should the restored originals be displayed?

The neo-Ruskinian view, which has now (after the excesses of architectural restoration in the 1950s and 1960s) a greater following in Italy than in its country of origin, views the detachment of sculpture from its setting with dismay. It is argued that the building is an organic whole: special treatment for sculpture not only scars the monument, but can distract attention from the need to address the underlying causes of decay. Moreover, replicas run up against the abhorrence for the falso, instilled in the present generation by the founding fathers of the Carta di Restauro.

A comparison of Donatello's St George, which left Orsan- michele in 1892, with St Mark, removed only in 1977, should be enough to convince the last romantics. Though St George's nose was repaired after a blow in 1858, his marble skin is otherwise intact, while St Mark's sharp edges have been crumbling for decades. Since his cleaning, three other of the Orsanmichele marbles have been treated with excellent results, and Verrocchio's bronze group of Christ and St Thomas will be finished by next year. Regardless of the rights and wrongs of replicas, it is essential that this campaign of safeguarding external sculpture by re- moval continue, and that it is extended to other vulnerable works, such as Cellini's Perseus and the groups by Rustici and Vincenzo Danti at the Baptistery.

No copy can ever be an aesthetically satisfactory substitute for the original, but the cast of St Mark, made from a silicone mould taken from the cleaned marble, has proved remarkably successful. Although the cast is exact, no attempt has been made to reproduce the traces of original gilding or to 'age' the surface artificially. There seems no reason why similar copies should not be made of the other Orsanmichele statues - though their status should be made clear to the public by a plaque on the building.

More urgent than decisions about copies is the provision of access to the originals. (After all, it took forty years before Michelangelo's David was replaced by a marble copy in the Piazza della Signoria). Fortunately, in the case of the Orsanmichele sculptures, suitable spaces are readily available: the saloni above the oratory, which were destined for exhibition use in the 1970s, but fell foul of the more stringent fire regulations enforced after the disastrous fire at Todi. If the niche sculptures were installed here - as has been advocated for decades - it is believed that public access, in groups of limited numbers, could be guaranteed. If so, it would be desirable to see Donatello's St Louis and St George (now in the S. Croce museum and the Bargello respectively) rejoining their original companions. One hopes that outrageously high admissions charges will not be levied: Italy's state museums are now so expensive (with no reductions allowed for foreign students) as to be seriously offputting to research on Italian art.

Removing the sculpture and treating the symptoms of its sickness does nothing, however, to cure the chronic disease of the monument. While the free-standing sculptures at Orsanmichele can be and are detached, their niches continue to decay in situ (Donatello's St Louis niche is the most conspicuous example). And even were the niches to be removed, the sandstone fagades behind would go on crumbling: few visitors realise that the scaffoldings sur- rounding so many Florentine buildings are not evidence of intent to restore, but parasassi to protect the passer-by from falling masonry. Only one carved capital remains on the piano nobile windows of the Palazzo Rucellai: the rest have been rubbed out in the last twenty years. The Palazzo Uguccioni in Piazza Signoria, recently uncovered after a scrupulously Ruskinian restoration, is scarcely distinguishable from a Roman ruin. So long as a proper traffic plan for the city remains a political football, and until the government is prepared to take effective measures against pollution, the carved surfaces of Florence will continue to disappear with terrifying rapidity.

In the face of the vast patrimony of sculpture in mortal peril out of doors all over the world, controversies about methods of cleaning sculpture housed inside seem somewhat overblown. Art historians are inclined to confuse dirt with patina (see p.844), or the relics of old restorations with the artist's final touch. This is not to deny the worth of 'natural' methods: the recent cleaning of Michelangelo's New Sacristy sculptures has been exemplary. But there are other pressing tasks ahead. Sometimes one wishes that Ruskin had spent less time rhapsodising over Ilaria del Carretto ('As a wave of summer sea', etc.) and more on rescuing the Fonte Gaia sculptures in Siena, which were brought inside long after it was too late.