Restorers using ultra-violet rays have rediscovered rich original details of Giotto's paintings in the Peruzzi chapel in Florence's Santa Croce church that have been hidden for centuries.
"We have uncovered a secret Giotto," said Isabella Lapi Ballerini, head of Florence's Opificio delle Pietre Dure, one of the world's most prestigious art restoration laboratories.
Last year, more than a dozen restorers and researchers began an ambitious project of "non-invasive diagnostics" to ascertain the condition of the 12-metre-high chapel, which Giotto painted in about 1320.
The aim of the study, partly funded by a grant from the Getty Foundation in Los Angeles, was to gather information on the 170 square metre chapel to use as a road map and "hospital chart" for a future restoration.
During the project, which lasted four months, restorers working on three stories of steel scaffolding noted that while viewing the paintings under ultra-violet light, they were able see amazing details not visible to the naked eye.
"It was something really astonishing," said Cecilia Frosinini, co-ordinator of the project that studied the scenes in the lives of John the Baptist and John the Evangelist.
"We knew we could get some very interesting results from our scientific diagnostics but when we looked under ultra-violet light, all of a sudden all these very faint paintings that were ruined by old restorations took on a new life," she said, pointing to one scene while donning protective eye wear.
Giotto's paintings in the lance-shaped chapel are believed to have had a major influence on Michelangelo, who was born nearly 140 years after Giotto died and who painted the Sistine Chapel in the early 1500s.
Today's restorers are seeing the details Michelangelo saw when he admired the paintings by Giotto, considered one of the artists who sowed the seeds for the Italian Renaissance.
"The scenes are again three dimensional... we were able to see all the chiaroscuro effects," she said. "There were bodies under the garments... they became three dimensional, you could see the folds of the garments, the expressions of the faces."
The Peruzzi chapel was immortalised in E.M. Forster's Room with a View, in the scene where the young Lucy Honeychurch is shown the Giottos by George Emerson, her future husband.
"It is the Giottos that I want to see, if you kindly tell me where they are," Lucy says. Forster continues: "The son nodded. With a look of somber satisfaction, he led the way to the Peruzzi chapel."
Commissioned by the noble Peruzzi family, it was whitewashed in the early 1700s to make way for a new chapel design.
But when restorers removed the white paint in 1840, they weren't exactly delicate. They used the techniques of their times, including harsh solvents and steel wool pads that blunted and homogenized the paintings, leaving them looking traumatised.
The 19th century "restorers" painted the parts of the Giottos that had been damaged, adding their own brushstrokes to highlight what was no longer visible from the ground.
In 1958, a restoration removed what the 19th century restorers added, leaving what remained of the original Giottos and what visitors to the church see today with their naked eyes.
Even though they are often referred to as frescoes, the Peruzzi scenes were actually painted a secco, or on dry plaster, unlike his famous frescos in the Bardi chapel, which is also in Santa Croce, or his works in St Francis in Assisi.
He painted the Peruzzi chapel toward the end of his life and some experts believe he was striving for a different effect than he achieved with the fresco technique, in which the painting is done while the plaster is still wet.
"It allowed him to obtain something more rich in terms of colours, of decorations," Ms Frosinini said. "But over time, dry painting is very fragile," she said.
Even after the 1958 restoration removed the "non-Giotto" parts added by 19th century "restorers," the paintings were left faint and anemic, like a patient who had never fully-healed.
But they come to life under ultra-violet light.
In the scene where God is accepting John the Evangelist into heaven, the wrinkles in John's forehead, the threads of his beard, the whites of his eyes and God's welcoming gaze appear like fleeting but powerful visions.
Unfortunately, they will remain fleeting forever.
The lush details are only visible when they are bathed in ultra-violet light and subjecting them to such constant bombardment would be not only impractical but harmful.
The only way to share the discovery with the public would be with a massive - and expensive - project to allow visitors to enjoy a virtual chapel on computer screens.
"I am fully aware that it is impossible to share the same kind of surprise and emotional feeling that we have when we are here in the dark and all of a sudden these images come back to life," Ms Frosinini said.
"So I just hope we can find enough funds to have a complete ultra-violet mapping of the whole chapel in order to build some kind of virtual software to share all that we have discovered with the general public," she said.