Art historical research continually uncovers new secrets, including overpainted details, encrypted symbols, revolutionary techniques, or previously unknown details about the artists themselves. Not to mention the countless theories and legends surrounding many works of art.
Technological advances have consistently brought new insights. In recent years, the examination of paintings using X-ray technology has particularly allowed new insights into art, including works by great masters, as seen in some selected examples:
(1) Artist: Jan van Eyck
The masterpiece of the medieval painter Jan van Eyck, the Ghent Altarpiece, contains one of the best-known "secrets" previously hidden under a layer of paint. The central panel of the altarpiece, also known as the Adoration of the Mystic Lamb, shows a mystical lamb symbolizing Christ, whose head was reworked at least once. To appear "more mystical," the lamb originally had eyes positioned at the front of its skull (like a human, not an animal). This was later overpainted with a "normal" sheep's head.
(2) Trade Secret
Many have wondered about the sudden shift to realistic representation in Van Eyck's works. Contemporary theories suggest the use of lenses and curved mirrors to easily copy the image onto the canvas. Such a mirror, for example, is found in the background of Van Eyck's "Arnolfini Portrait." Although this theory is often dismissed as a Renaissance invention, it is believed that such practices were already widespread during the artist's lifetime but were kept secret as trade secrets.
(3) Artist: Michelangelo
Michelangelo Buonarroti, who described himself as a "sculptor, not a painter" of the Renaissance, provided art history with several secrets in his famous frescoes in the Sistine Chapel. Since the works were so high up that detailed viewing was difficult, the artist included some not-so-subtle details.
It is now widely known that his depiction of God in the Creation of Adam, with surrounding angels, closely resembles a cross-section of a brain. Given the Renaissance was a time of anatomical research, many believe this resemblance was intentional, though its interpretation remains debated.
In another fresco in the chapel, Pope Julius II is depicted as the prophet Zechariah with two angels, despite Michelangelo's known dislike for him. Upon closer inspection, one angel makes a vulgar hand gesture towards the Pope, comparable to today's middle finger.
It's not surprising that in the Last Judgment fresco, a figure interpreted as Julius II is suffering in Hell. This fresco was also an overpainted work: Michelangelo originally painted all figures nude, which was controversial at the time. Daniele da Volterra was later commissioned to add minimal clothing, earning him the nickname "braghettone" ("breeches painter"). The last restoration aimed to return the fresco to its original state, a literal "revelation" that also revealed much brighter colors.
(4) Artist: Rembrandt
Rembrandt van Rijn's Night Watch is also affected by such a color change. The painting depicts one of Amsterdam's militia companies, but not on a night patrol. Over the years, additional dirt caused the already dark painting to appear as a night scene, so the work should more accurately be called "Day Watch."
Modern techniques also revealed a sketch beneath the painting, which was later overpainted, confirming theories that lacked proof until recently. Rembrandt's works often contain overpainted layers; his portrait of a man, for instance, hides an unfinished painting beneath its surface.
(5) Artist: Van Gogh
Some "secrets" can be seen with the naked eye if one knows what to look for. Michelangelo's brain in the Last Judgment is one famous example. Van Gogh's Starry Night, according to researchers, illustrates the principle of turbulent flow, a physical concept describing the random, varying eddies in fluid movement, an unsolved scientific problem, yet the painting closely matches current models.
Like many artists, Van Gogh's paintings often have overpainted layers. Canvases were expensive and money was tight, so he reused some earlier works. Later paintings were also overpainted: beneath his Grass Ground, a dark female portrait was found, and under the Ravine, wild vegetation was hidden.
(6) Trade Secret
Van Gogh benefited from the Industrial Revolution's advancements, with chemical research introducing around 20 new pigments. These bright colors are partly due to Van Gogh's vibrant works. Unfortunately, many pigments contained toxic substances like lead, arsenic, or mercury, which were also sold as insecticides. Researchers now consider it likely that these pigments contributed to Van Gogh's poor health.
(7) Artist: Leonardo da Vinci
Leonardo da Vinci, perhaps more than any other, remains enigmatic in the art world. Studies of his Lady with an Ermine revealed three versions: one without an ermine, one with a gray-furred ermine, and the final with white fur. The animal was added later, making it originally just a "Portrait of a Lady."
Leonardo's works often spark speculation and theories. Elements in The Last Supper have been interpreted as musical notes for a melancholic melody, and no other work has been subject to more rumors and conspiracy theories than his Mona Lisa. Many have tried to uncover secrets such as the reason for her "cryptic" smile or missing eyebrows, though most of these speculations hardly qualify as art historical research.
Historically significant is the discovery of a "second" Mona Lisa, also attributed to Leonardo and older than the Louvre's "original." This work remained mostly unknown until 2012, as it was mostly in private collections and rarely exhibited. The Mona Lisa's understanding might need reevaluation due to this find.
(8) Artist: Caravaggio
Michelangelo Merisi da Caravaggio's "secret" is less theoretical. Known for his atmospheric paintings, he created The Lute Player around 1595 in two versions. The central figure was long interpreted as female, so much so that in Russia (where it is displayed in the Hermitage Museum in St. Petersburg), it was known as "Lyutanistka," the "Lute-playing girl."
Although some still consider the figure's gender unknown, it is now widely accepted to be a young man. Art historians support this with the figure's flat chest and similar depictions where Caravaggio's young friend Mario Minniti posed, such as Boy with a Basket of Fruit and Boy Bitten by a Lizard.
(9) Trade Secret
The use of a camera obscura in Baroque paintings is now well-known. Artists used a darkened room to project the image onto their canvas through a small opening or lens.
Research has shown that Caravaggio used light-sensitive materials in his paintings. It is believed that a mixture of white paint and glowworm powder created a short-lived copy visible in the dark, which was then transferred to a visible sketch—a kind of early photography.
(10) Artist: Vermeer
In a work by Jan Vermeer van Delft, a well-hidden "secret" was found—an element concealed under multiple layers of paint. His Girl Reading a Letter at an Open Window originally included a naked Cupid in the background, which would have made the scene's interpretation much clearer. Thus, the girl was originally reading a love letter, while in the final version, she could be reading "the emotional equivalent of a tax return." Previously, the sparse walls in Vermeer's paintings were often interpreted as a sign of chastity, something this change now disproves.
Art Historical Research in the Coming Years
These insights are just a small part of what modern technology can uncover in artworks. Continuous technological progress brings new methods and tools, revealing previously unknown secrets.
Current research methods are far from fully exploited. Many famous paintings remain to be examined—Rembrandt's Blinding of Samson, for instance, is still under X-ray analysis in Frankfurt.
Art historical research is something to watch in the coming years.
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