How long would it take to clean Rome's Colosseum using toothbrushes?

Archaeologists embarking on the mammoth task of cleaning the Colosseum, the world’s most recognized Roman monument, have hit on a secret weapon: the humble toothbrush.

Toothbrushes – of the sort available in any corner store or pharmacy – are proving the ideal tool for scrubbing away the centuries of grime that coat the exterior of the giant amphitheater.

The simplicity of the tool contrasts sharply with the magnitude of the task of keeping the Colosseum and other architectural icons of Rome clean and intact. But the Colosseum effort, which is being sponsored by a private company, is seen as a model for how the state can protect its cultural treasures – and give them long overdue care.

“This is the first time in the 2,000 year history of the Colosseum that it’s been cleaned,” says Cinzia Conti, an archaeologist and the technical director of the project.

Brushes and water

The technicians, engineers, and archaeologists who make up the restoration team are not relying solely on toothbrushes, of course. But their other tools are equally basic. “It’s really a very simple system that we are using, and it is economical," says Ms. Conti.

Larger scrubbing brushes are also being used to remove the caked-on dirt from the huge blocks of travertine marble that were used to build the monument nearly 2,000 years ago. And the thick black calcium deposits that encrust much of the amphitheater are first softened up with water, which is sprayed in a fine mist through nozzles attached to yellow pipes. The water is unheated and contains no detergents.

“It’s an environmentally friendly way of cleaning. The only thing that flows away is dirty water but there are no chemicals in it,” says Conti. “Under the layers of dirt, chemical reactions can take place – chalky deposits form, as well as algae. That eats away at the stone. It’s like a cancer and we need to cure it.”

For the most stubborn bits of calcium and entrenched grime, the technicians use delicate drills, of the type wielded by dentists on nervous patients.

The drills enable them to scour away at the travertine marble inch by grimy inch, returning it to its original color – not blinding white, but a soft, creamy ivory.

Occasionally small chunks of stone fall off, clattering onto the multiple layers of scaffolding that have been erected around the amphitheater. They are carefully numbered and laid out on benches, from where they will be reattached with a specialized type of glue consisting of water and marble dust.

A new model for preservation?

The project, which is expected to be completed in October 2016, is costing 25 million euros ($35 million) and has been sponsored by Tod’s, an Italian shoe and luxury goods company.

It took years for Rome to accept the offer made by Tod’s owner, the billionaire businessman Diego Della Valle,, after it became embroiled in bureaucracy and squabbling between officials.

The revolving-door nature of Italian politics hardly helped. “Since we started discussing the project three years ago, we have had to deal with five different cultural heritage ministers,” says Mariacristina Modonesi, the director of communications for Tod’s.

Italy has struggled for decades to maintain its huge number of historically important sites, ranging from Pompeii, the Roman city buried by the eruption of Mt. Vesuvius, to Renaissance palaces.

The state just does not have the money to pay for the preservation of so many gems. The fact that the cleaning of the Colosseum is being paid for by a corporation is being seen as a blue print for the future.

It has already inspired several similar projects, with the fashion house Fendi financing a $2.8 million restoration of the Trevi Fountain in Rome, famed as a setting for the film "La Dolce Vita," and an Italian clothing company, Diesel, paying for the cleaning of Venice’s historic Rialto Bridge.

The experts hope that the clean-up will not have to be repeated for a long time to come, particularly if Rome city council makes good on promises to close to vehicle traffic the Via dei Fori Imperiali, the broad avenue that runs just a few yards from the Colosseum.

“If they can get rid of the cars, then all the work we are doing here will be preserved,” says Conti. “With more low emission cars in the future and less pollution, the restoration could last for 200 years or more.”

'Marks of the past'

Standing on the scaffolding, one is able to see the tiny scratch marks made by the iron chisels which the Romans used to shape and refine the blocks of stone.

Construction of the Colosseum started around 72 AD under the Emperor Vespasian and was completed a decade later by his son, Emperor Titus. The giant arena was used to stage fights between gladiators, wild animal hunts, and public executions.

The restoration has revealed new details about the monument – for instance, the extent of a devastating fire that swept through the building in the third century AD and the repairs that had to be carried out afterwards. “There are stones which still bear the scars of the fire,” says Conti.

As the restorers strip away the thick black crust and streaks of green algae that cling to the monument, they reveal a pinkish patina that has formed naturally on the travertine stone.  

The patina, a type of oxidization, does no harm to the surface of the stone and in fact protects it from urban pollution, so it is left intact.

“The Colosseum is like an old person with lines and wrinkles. We don’t want to do a facelift, just a cleaning,” says Rossella Rea, the director of the Colosseum. "It’s important to retain the marks of the past – they are part of its history."