The words are scrawled in pencil in a corner of one of the world’s most iconic works of art, visible only to those who are looking for them. An image of a blood-red sky obscures the tiny print, hovering above a ghostlike figure with his hands to his head and his face contorted into a wail.

“Can only have been painted by a madman,” the message reads.

The author of the cryptic note etched into “The Scream,” by Norwegian painter Edvard Munch, has intrigued art historians, who debated his identity for 117 years. Now, researchers believe they know who’s behind the enigmatic phrase.

“The Scream” was unveiled in 1893, inspired by a walk Munch took at sunset with two friends. As he paused with exhaustion to lean against a fence, he later said, he saw “blood and tongues of fire” rise above the dark fjord flowing below him. “My friends walked on, and I stood there trembling with anxiety — and I sensed an infinite scream passing through nature,” Munch wrote.

No one seems to have noticed the penciled-in sentence until a decade later, when a Danish art critic posited that it was probably written by a vandal’s “tactless hand.” Curator Gerd Woll bolstered the theory in 2008 when she suggested that the inscription did not come from the artist.

Curators at the National Museum of Norway announced Monday that they had discovered the person’s identity while preparing the Expressionist masterpiece for display in a museum building set to open next year.

The conclusion took more than a century because, for a long time, art historians were tired of researching Munch’s biography. They didn’t even attempt to investigate the inscription, which was written in old-fashioned Norwegian, said Mai Britt Guleng, a curator at the museum specializing in old masters of modern art.

“We wanted to ask other questions,” she said in an interview. “But now, maybe we are ready to go back to a more personal aptitude and try to understand him as an artist who created by not abiding to the rules.”

Curators used an infrared camera to snap photos of the painting, which gave them a better view of the inscription. Then they compared the sample to thousands of pages of Munch’s notes and letters.

The handwriting was a match. The vandal was the painter himself.

There had been some obvious clues. The phrase’s tiny size would have been an unusual choice for someone seeking to disgrace the artwork, Guleng said. Munch also never chose to paint over the sentence while he was alive, suggesting that he was fine with it.

Though some proposed that Munch may have written the phrase, they produced little evidence to support the idea, Guleng said. As far as she knows, no one ever asked Munch directly whether the inscription was his — and he may not even have remembered writing it.

“He might have been drunk doing it,” Guleng said. “It might have been a moment of emotional distress. But he never mentioned it later.”

Guleng theorizes that Munch wrote the phrase shortly after an uncomfortable confrontation in 1895 while he was displaying the painting for the first time in the city of Kristiania, now Oslo. During a public discussion of the piece, a young medical student speculated aloud that the grotesque painting showed that Munch must have been deranged.

The student suggested that Munch was abnormal, prone to hallucinations and even degenerate, a suggestion that Guleng said implied that the significance of his work would die with him. Perhaps, the student speculated, Munch should be hospitalized and prevented from making art.

That Munch had been trying to help people better understand his work heightened the criticism’s sting, said Jill Lloyd, a writer and curator specializing in Munch and 20th-century art. Munch had begun to portray his work as a collection that reflected the cycle of life and death.

“If people could see his whole vision of life, they would perhaps find the paintings more easy to understand,” Lloyd said. “So he was shocked and hurt when people were saying that he was mad.”

A thin-skinned man, Munch carried the disapproval for years, in part because his family had a history of mental illness that he feared would also find him. Nearly four decades later, Guleng said, Munch argued in private letters that the student had been wrong to assume that “The Scream” suggested mental instability.

Addressing sickness, death and anxiety in art was not a sign of illness, Munch said, but an indication of health. He embraced the idea of a “genius mad artist” who could see parts of the world that others could not — a popular concept in late 19th-century art.

Munch’s note that “The Scream” must have been painted by a “madman” was an ironic comment that showed he did not abide by anyone else’s rules, Guleng said.

“He was also showing how vulnerable he was by doing this, how hurt he was, and worried,” she said. “And in a way, he was taking possession of his own life. He was taking control of the situation.”

The discovery of the inscription’s author is the second news-making event for this version of “The Scream,” which was stolen from Norway’s National Gallery in 1994. The piece was recovered at a hotel three months later as a result of a scheme in which police posed as another museum’s curators seeking to buy the painting.

Solving the mystery of the hidden message marks another chapter of the artwork’s history. The resolution sheds new light on Munch’s personality, Guleng said, and demonstrates the bond between him and his work.

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