The history of the restoration is fascinating, not just “because of the information it will provide about Leonardo da Vinci’s working methods, of which we are lacking data,” says Ana González Mozo, author of the technical study, but also for some of the conclusions obtained. The most fundamental of these, of which Prado restorers are evidently proud, is the relative simultaneity between the Leonardo original and the copy. “The work has highlighted that the painting was made in parallel with the original portrait,” says the report. This is the first time there has been proof, say gallery restorers, that a copy of the Mona Lisa was made “live.”

To carry out the four-month restoration, Almudena Sánchez cleared away the oxidized varnish, did away with the horrendous black paint covering the background landscape (added in the 18th century, according to the report) and the veil and hair of subject Lisa Gherardini on the left side of the portrait, and finally reinstated the colors that returned the copy to its original state. “It opened a window that had been closed for two centuries,” she says.