The Da Vinci Question

La Bella Principessa

Is this portrait the work of Leonardo da Vinci? Image courtesy Science Television Workshop.

In 1482 the 30-year-old Leonardo da Vinci offered his military services to Ludovico Sforza, the duke of Milan. Leonardo, an expert on machines of war and industry, as well as one of the world’s greatest artists, spent the next 17 years under the patronage of the ruling Milanese duke. His studies during this time included flying machines, anatomical studies, war engines, submarines, architecture, and about six completed works of art, including The Last Supper, which revolutionized art in Renaissance Europe.

Fast forward to the 21st century and an August 2008 article in the New York Times that introduced readers to an obscure work of art. Now known as La Bella Principessa, the small portrait is of a young woman in profile, about 14 years old, drawn with chalk, ink, and dye on sheepskin and mounted on an old oak board. While its exquisite beauty is undeniable, of far greater interest was the question of the unknown painter. Was it or wasn’t it the work of Leonardo da Vinci?

The first official mention of this portrait appears at a 1998 Christie’s auction. The buyer, New York art dealer Kate Ganz, purchased the piece, which was listed as an early 19th-century German Romantic portrait, for $19,000. In 2007 Canadian-born collector Peter Silverman purchased it from her on behalf of an anonymous Swiss collector for $21,850. The close profile view and line strokes suggested an earlier provenance, so Silverman asked Renaissance scholars to look at the portrait. Soon the “L” word was buzzing around the art world. Could it be? Various Leonardo scholars suggested it just might be. But first science would have to meet art in a scholarly dance of authentication.

Giammarco Cappuzzo, an art consultant and a friend of Silverman’s, sent a tiny slice of the sheepskin to the physics department at the University of Zurich’s Institute for Particle Physics for carbon-14 dating. The results conclusively dated the vellum to between 1449 and 1656 (Leonardo died in 1519). Yet while the date might fit, the material did not. Leonardo left behind many beautiful drawings and some paintings, but this particular artwork was an anomaly: a formal portrait on vellum, or sheepskin, a material used for manuscripts and one that Leonardo had never been known to use for his formal portraits.

As a professor teaching a course on Leonardo and a producer of a PBS limited-edition series—Science+Art—exploring the intersection of science and art, I wanted to know more. What better way to illustrate the meeting place of science and art than through the authentication (or not) of a possible Leonardo. Either way, I knew the footage would be compelling. I asked my series adviser Martin Kemp, an Oxford art historian and one of the foremost Leonardo scholars, if we should look into this. Kemp had already done preliminary research and had even been asked to examine the real thing, but had refused to act as a paid authenticator, a role that ethically would have placed him in an awkward position. But now, with the Science+Art project underwriting all of Kemp’s expenses, he agreed. The October after the New York Times article appeared, I gathered my director of photography, Vic Losick, and Kemp—and set off for France to see scans of the artwork firsthand.

Simulacrum of a Young Lady

Our first stop was the office of Lumiére Technology, located in a lovely interior courtyard along Paris’s Left Bank. There we met Pascal Cotte, the company’s chief technical officer and cofounder. Cotte, an optical engineer by trade, invented the first 13-band multispectral camera, which can scan and digitize images to an extraordinary resolution of 420 million pixels. Contemporary professional cameras have a resolution of 16 million pixels. In addition, the multispectral portion of Cotte’s camera allows for scanning beyond the capabilities of the human eye—from ultraviolet to infrared. These scans above and below the visible spectrum reveal the normally invisible layers of sketches behind the painting and in much greater detail than can an X-ray. With the ultraviolet scans a conservator can also differentiate original work from subsequent restorations on that work. Conservators can not only see how a painter built up his painting from an initial sketch; they can also isolate the chemical components of the paints and pigments used, thus helping date a painting. The scans take only a few hours at most, as opposed to other methods of digitizing art in detail, which can take days, turning this multispectral camera into a powerful tool for conservators of art and for museums.