Known for her smoky eyes and taunting smile, the Mona Lisa is one of the most famous paintings in the world. Now, after taking a closer look at the beloved Renaissance masterpiece, researchers have found evidence that Leonardo da Vinci actually relied on a charcoal underdrawing to render the sitter’s mysterious features.
As Sarah Cascone reports for artnet News, scientist Pascal Cotte—who detailed his findings in a recent issue of the Journal of Cultural Heritage—started studying the Mona Lisa in 2004, when the Louvre asked him to digitize it with his high-resolution, multispectral Lumiere Technology camera. Colette then used the layer amplification method, which allows scientists to amplify weak infrared signals and reveal new details about paintings, to detect traces of the hidden underdrawing.
Ultimately, Colette captured more than 1,650 photographic scans. He’s spent the past 15 years analyzing this data with the help of co-author Lionel Simonot, a physicist at the University of Poitiers.
“These discoveries increase and increase the mystery of [the Mona Lisa’s] creation,” Cotte tells Express’ Josh Saunders. “[I]n the end we understand that it is the work of a very long ‘creative act’—which spans more than a decade and in several stages.”
The new analysis suggests that Leonardo used a technique called spolvero, which enabled him to transfer sketches from paper to canvas using charcoal dust, to paint the Mona Lisa.
Speaking with artnet News, Cotte says, “The spolvero on the forehead and on the hand betrays a complete underdrawing.”
Leonardo likely created the Mona Lisa between 1503 and 1519, when he was living in Florence, per Encyclopedia Britannica. Though the subject’s exact identity remains unclear, many art historians believe that she is Lisa Gherardini, the wife of a Florentine merchant. Others speculate that the Mona Lisa may be a more allegorical figure. According to Cotte, the presence of what may be a harpin in the sky above the Mona Lisa’s head could indicate that the sitter is an allegory for justice or goodness.
“This hairpin in the sky just to the right of Mona Lisa’s head cannot belong to a portrait of a person because in the city of Florence this was not the fashion at the time. People had to be dressed in certain ways to denote their profession and for nobility respecting the colors,” Cotte tells Express. “It is not possible for Mona Lisa to have hair like this, it was impossible of the time in the city of Florence.”
Art lovers around the world often call attention to the painting’s smoky, dream-like appearance. Leonardo accomplished this effect through a variety of painting techniques, including sfumato, or fine shading that creates seamless transitions between light and shadow.
The Mona Lisa is also known for her arresting stare; her eyes seem to follow viewers as they move across a room. Cotte’s new discovery could help account for this effect: As Tessa Solomon notes for ARTnews, the spolvero marks indicate that Leonardo may have shifted his subject’s pose and made her stare more directly at the viewer.
This isn’t the first time that Cotte has identified hidden features beneath the Mona Lisa’s surface. In 2015, the scientist made headlines by claiming that Leonardo painted the likeness seen today over an earlier portrait of an entirely different woman.
But many critics and scholars objected to this interpretation: Instead, art historian Martin Kemp told BBC News’ Roya Nikkhah, the details revealed by Cotte’s Lumiere Technology are likely a reflection of “a continuous process of evolution.”
The Guardian’s Jonathan Jones echoed Kemp’s assessment, suggesting that Leonardo worked on the painting throughout his life, adding details as his artistic philosophy developed.
“Of course he did not do anything so banal as paint someone else on top of his portrait of a Florentine woman,” Jones argued. “What he did was so much more fascinating. He worked on this portrait until the face of a real person was transformed into a myth.”