A new study on the Mona Lisa has revealed evidence of a charcoal underdrawing, suggesting for the first time that Leonardo da Vinci used a preparatory sketch to create the famous portrait.
The underdrawing, detected by multispectral analysis, was likely created using the spolvero technique, a method for transferring a sketch to canvas in which holes are pricked along the outline of an image and dusted with charcoal.
The study was conducted over a 15-year period by scientist Pascal Cotte, who published the findings with Lionel Simonot in the Journal of Cultural Heritage. In 2004, Cotte was invited by the Louvre to digitize the Mona Lisa with his pioneering Lumiere Technology camera, a high-resolution multispectral camera, which is capable of detecting light reflected over 13 wavelengths. The Lumiere technology also employed modern infrared reflectography, which is used for detecting charcoal underdrawings through faint light reflected on the charcoal’s surface.
Cotte detected the spolvero marks in the Mona Lisa’s hand and hairline—the lighter areas of the painting—which revealed that Leonardo shifted her pose, turning her head to stare more directly at the viewer. The analysis noted too what appears to be a hairpin, which only invites more questions as the accessory was not in vogue in Florence at the time of the portrait’s creation. In an interview with the Express, Cotte said that the detail may have been allegorical, as the hairstyle was used more typically in depictions of goddesses or the Virgin Mary.
The study also stated that the drawing may have been used to create more replicas of the painting, such as the one displayed in the Prado in Madrid, which owns the earliest known studio copy of the Mona Lisa.
“These discoveries increase and increase the mystery of its creation, in 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,” Cotte said.