The sculpture has been digitally mapped to find cracks and blemishes
A dispute over how to clean Michelangelo's famous David statue in time for its 500th birthday next year has caused a stir in the art world.
The row centres on whether the statue should be cleaned using water to restore it to its original state or by a dry cleaning method which would be less radical and only remove the worst grime.
A petition has been signed by 39 international art experts to stop Florence's Galleria dell'Accademia using their planned wet technique and demanding that an independent commission should decide on the best method.
Restorer Agnese Parronchi, who was employed to carry out the project, resigned in April, saying that only hair brushes should be used to clean David.
The restoration is expected to take six months
The statue was partly what time and grime had made it and that the Academy's preferred technique would make its surface too uniform, hiding the natural colours and veins of the marble, she told the UK's Independent newspaper.
But director of the gallery, Franca Falletti, said the brushing method would only remove dust and a wet clean would make David appear closer to the icon of eternal youth that Michelangelo intended.
Celebrities including Sting and Mel Gibson are considering donating as much as £500,000 to the project, which has been largely funded so far by a Dutch philanthropist.
The Italian Government has also backed Ms Falleti's argument and given the go-ahead for the restoration to begin in September.
"The final decision on cleaning the David masterpiece rests with the superintendent of Florentine art. He has been known to heed international protest on similar sensitive issues, so he could yet change his mind," Brian Barron, the BBC's Rome correspondent said.
He also said there had been complaints that restoration of some of Michelangelo's painting had made the colours brighter than they had originally been intended.
In response to the art experts' petition, Antonio Paolucci, superintendent for arts in Florence, said the Italians, "didn't need to be told what to do by anyone".
"We are the best, on an international level, in the field of restoration. There is no need to dramatise what is just a light dusting, under supervision," he said.
More than 1.2 million people see the statue every year
The big clean has been painstakingly planned over the past 11 years, involving every inch of the masterpiece being digitally mapped for cracks or blemishes.
The restoration work is due to be carried out outside visiting hours over a six-month period.
Michelangelo's statue spent more than 300 years in the Piazza della Signoria before moving to the Galleria dell'Academia in 1873.
Since then, an average of 1.2 million visitors have seen the sculpture each year.