Leonardo's Lost Princess (7 page)

We get no other pride than to remain ourselves, innovative, listening to art historians, experts, collectors and players of museum life whose knowledge we seek only to enrich by providing them new evidence, scientifically proven for more certification. We are not art historians. We are experts in scientific imagery for fine arts. Like it or not, these scientific measurements of multispectral paintings open a new area of investigation, in the same way that medical imaging has enabled practitioners to work better. These images should be commented on, analyzed, compared and shared. Deny to Lumiere Technology, inventor of such process, the right to exist and to comment on the images under the pretext that we are not art historians is nonsense. Like radiologists, we provide a checkup, a first observation, and then refine it for other professionals. The only requirement for expertise and study is the use of more efficient tools to search for the truth. The multispectral analysis, as a scientific measurement of the substance of the artwork, seems to be one of the most sophisticated, if not the most successful. It is never too late to recognize a breakthrough and to use it.
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On a spring day in 2008, I rode up to the front entrance of Lumiere Technology on the back of Cappuzzo’s Vespa scooter, clutching the portrait in my arms. (Kathy nearly fainted when she learned about my cavalier means of transporting our priceless lady. I don’t know what I was thinking—perhaps it was a reckless yearning to spit in the face of propriety. Fortunately, we arrived safely!) I carefully dismounted and carried my precious package into the building, where I was greeted by a beaming Pascal Cotte. I liked him immediately. He was vibrating with warmth and enthusiasm. I turned over my treasure, telling him only that it had been attributed to an unknown nineteenth-century artist.

He asked me to be seated while he took a quick preliminary look, and he disappeared with the package. He was back within half an hour, his face flushed and his eyes gleaming. He bounced excitedly on the balls of his feet. “Do you know what you have?” he asked.

I feigned ignorance, not wishing to let him know I knew. I wanted him to form a totally independent opinion.

“On a hunch, I ran a digital scan of your drawing through my database and came up with many similarities that intrigued me,” Cotte said. “I believe this may be a portrait by Leonardo.”

I grinned and admitted my suspicions. “I didn’t want to influence you,” I explained.

Cotte was trying to contain his enthusiasm and view the matter objectively. This was a different challenge than investigating a painting like
Mona Lisa
, which had a proven authorship. Could he also use his technology to
detect
authorship?

With Cappuzzo’s help making arrangements, we sent a tiny sliver of the vellum to be carbon-dated at the Swiss Federal Institute of Technology in Zurich. This was a crucial part of the authentication. If it were determined that the parchment was of a later era, all bets were off. And so the process began.

Carbon-14 dating is a chemical examination based on the way natural elements age, and it can be used to test a material or substance that has a biological origin—such as vellum, cloth, or wood. Carbon is breathed in by animals and plants through the carbon dioxide in the atmosphere. Carbon-14, one of three carbon isotopes, is radioactive and subject to decay over a very long period. Its half-life is 5,730 years, which means that in that period, half of the carbon-14 isotopes will have decayed. By measuring the percentage of carbon-14 that remains in a test sample, it is possible to determine its age to within two hundred years.

The most famous and controversial case of carbon-14 testing involved the Shroud of Turin, the cloth that is alleged to have been the burial shroud of Jesus. In 1988, carbon testing revealed that the age of the cloth was medieval, which means it could not have belonged to Jesus. That might have settled the matter once and for all, but there was so much interest in the Shroud of Turin, and so much passion among true believers about proving its authenticity, that speculation raged about possible explanations for the “false” result.

In 2005, Raymond N. Rogers, a highly respected chemist and a fellow of the Los Alamos National Laboratory, revealed in a scientific journal that the entire cloth was much older than the test sample—at least twice as old, and possibly two thousand years old. The explanation: the corner that was tested had been subject to mending and thus contained newer material. Rogers’s discovery did not stop the controversy, and studies of the Shroud of Turin continue.
13

We knew that carbon-14 testing could not authoritatively establish that our portrait had been created in the fifteenth century, much less in Leonardo’s lifetime. But it
could
contradict the Christie’s attribution of the nineteenth century, and that’s what we were after. The carbon dating of the vellum showed that the drawing had with great probability been done between 1440 and 1650, which was within the perimeters of a fifteenth-century authentication. It was important evidence, although carbon dating alone wasn’t proof. Art forgers were known to use materials from a desired era. For example, Hans van Meegeren, who created phony Vermeers, used canvas from the seventeenth century. Nevertheless, the carbon dating was a first positive result in a long checklist, and Cotte and his technicians began their study in earnest.

Cotte’s scientific method did not ignore the processes of art anthropology; it just made it easier to view the evidence. Much of Cotte’s investigation involved the details of style, fashion, and era as well as a comparative analysis with Leonardo’s other signature works. Science does not replace aesthetic sense, historical study, or any of the other expert means of authenticating works of art. It merely adds another layer of proof.

Cotte began by digitizing the portrait at a resolution of 1,570 pixels per millimeter, an extraordinary level of definition. At this resolution, the slightest nuances and tiniest details––the
craquelure
(network of fine cracks on the surface), the grainy surface texture of chalk or graphite, and even fingerprints––were perfectly visible.

In a single scanning session, which lasted only one hour, the work was measured and captured in thirteen spectral bands, and the multispectral camera recorded and generated approximately 24 gigabytes of digital data. Cotte’s goal was to produce an image that contained additional information: what could be seen beneath the various paint layers, since many pigments that are opaque to ordinary visible light are transparent to infrared. Cotte explained:

The study or analysis of images of such ultra high resolution and high definition gives the researcher a considerable weapon––a trump card, if you will. A few hours spent before a large computer screen, armed with images produced by a multispectral camera, can be invaluable, complementing the evidence obtained in a traditional conservation studio. The high degree of sophistication and extreme precision of multispectral images enable an in-depth study of the object’s physical characteristics, reducing the need for further direct contact, since the work is handled only once in the initial scanning session.
14

The results:

• Perfectly clear, ultra-high-resolution images
  
• Normalized (standardized) colors with a unique level of accuracy
  
• A broad spectral range, with infrared and raking light infrared images extended to 1,050 nanometers (instead of the 850 nanometers possible from film)
  
• Information that is more pertinent and discriminating
  

With this new method of investigation, the colorimetric print was born. Works of art can now be compared on an accurate scientific basis. With digital reconstruction, multiple combinations of data can be explored from different points of view and for different purposes.

Recalling his initial impressions of our portrait, Cotte wrote,

When the portrait was first presented to us, it was described as a watercolor, a colored drawing, or, alternatively, as a drawing in wax crayons, chalk or pastels. No one was exactly sure of its technique. That the technique had not previously been accurately described is almost certainly due to the later restorations, which masked the media of the original drawing . . . the portrait is drawn on the smooth hair side of the vellum rather than the rough side. This provides an important clue, for some techniques can only be carried out on the flesh side, which results in an entirely different appearance.

The multispectral images enabled us to identify accurately the media of the portrait. It is executed in the technique generally termed
à trois crayons
, that is to say, with finely sharpened pieces of natural black, red and white chalks. This mixture was combined with pen and ink, especially in the areas of hatching. Pen and ink was a favorite technique of Leonardo’s, as was red chalk (of which he may have been an early pioneer). Although generally associated with later periods (especially the 18th century), the
trois crayons
technique has been used for portrait drawings since the Renaissance. To be completely effective, it requires a toned or colored support to set off the white highlights. In early periods, artists often exploited the natural flesh colour of vellum or parchment, mixing red and white chalks on top of it to reproduce the sitter’s complexion.
15

Aided by his illuminating camera, Cotte was able to present a clear view of the media used in the portrait. He found that the basic contours and shadows were executed in black chalk, strengthened in pen and dark brown ink—once again, a typical technique of Leonardo’s. A detail at the junction of the subject’s bodice and neckline showed traces of strokes of all three chalks against the flesh-colored midtone of the vellum. The way in which the artist exploited the support is particularly clear in another detail: the eye, where the untouched golden tone of the vellum conveys the amber color of the subject’s iris.

Cotte and his digital detectives carefully studied the innovative media technique, analyzing the chalks used (black, red, and white) and their mixture with pen and ink; examining the stylistic parallels with known Leonardo works; and cataloguing the period details of style and dress. They found that the interlace ornament in the costume corresponded to patterns that Leonardo explored in other works. They easily determined that there were noteworthy similarities between our portrait and Leonardo’s
Lady with an Ermine.
These included the modeling of flesh tones using the palm of the hand, the intricacy of the patterns of the knot-work ornament, and the treatment of the contours.

Each of these pieces of evidence was significant in the slow building of a case. But another test of authenticity when studying Leonardo is whether there is mathematical precision in the anatomy. Leonardo’s rules of anatomy are well known and described in his notebooks and teachings. Most famous is the drawing
Vitruvian Man
, which depicts a male figure in ideal proportions. Cotte’s digital equipment allowed the level of high resolution that made this examination possible.

It was Leonardo who first called the eye “the window of the soul,” and his fascination with the eye’s anatomy and transcendent function is obvious in all of his portrait works. For this reason, Cotte paid special attention to the eye of the lady in profile. “Some of this might seem obvious or universal,” he explained, “but the way each artist handles these features is more individualized than one might imagine, and their combination is unique. Leonardo, for example, consistently made the bottom of the eye’s iris coincide exactly with the edge of the lower eyelid, and it is surprising how few portrait artists took the time to render the delicate lower eyelashes of their sitter.”
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Once again, Cotte was aided in his comparison by an earlier digitalization of
Lady with an Ermine
, Leonardo’s rendering of Cecilia Gallerani. Scrutiny of the two pieces showed a thrillingly identical treatment of each detail, including the outer corner of the eyelid, the fold of the upper eyelid, the contour of the iris, the lower eyelashes, the upper eyelashes, and the juxtaposition of the edge of the lower eyelid with the bottom edge of the iris.

Recall that in her evaluation of the drawing (see chapter 2), Mina Gregori had also noted the eye, stating, “In my view, exact parallels in the brightness and transparency of the girl’s eye are only to be found in other examples in the drawings of Leonardo.”

The anatomical details offered further proof through the unique Leonardo attention to measurement in the construction of his subject. Cotte found that the proportions of the head and face reflected the strict rules that Leonardo outlined in his notebooks. Yet even though these measurements added to the body of proof, there was much work still to be done. This magnificent process would open up the discussion between old school and new school. Old school uses connoisseurship; new school brings in technology as well. New school methods merely confirm or disprove; they don’t change the art or replace the eye. The eye still comes first.