James Castle, Untitled, found paper, soot, and color of unknown origin, Smithsonian American Art Museum, Gift of the James Castle Collection and Archive and museum purchase through the Luisita L. and Franz H. Denghausen Endowment. (Smithsonian American Art Museum/Smithsonian American Art Museum)

When Gail Johnson, 68, and her 79-year-old sister Georgia Allred go shopping, the latter always pauses at the checkout counter and says, “Thank you, Uncle Jim.” That, Johnson explains, is because sales of their late uncle James Castle’s works are keeping the sisters afloat financially.

“We don’t have a lot of money,” Johnson says. “He has provided to supplement our retirement.”

Castle, a self-taught artist who was born deaf and lived in Idaho until his death in 1977, never learned to read, write or sign. His materials included soot and spit, and subject matters ranged from nonsensical configurations of letters and stylized portraits to interiors and landscapes, which reflected a sophisticated understanding of perspective.

Many aspects of Castle’s life and work are mired in controversy. Some have diagnosed him with autism or mental illness posthumously — an even more contentious undertaking, given the many gaps that remain in the artist’s biography. The family, for example, maintains that Castle was born in 1900, while a researcher found a church ledger that set his birth a year earlier. “I choose to believe Grandma, who bore him, over the Catholic Church records,” says Johnson.

The artist’s niece is concerned that outsiders are embellishing her uncle’s life rather than telling the truth. “People just say more than they need to say,” Johnson says. “You get a bunch of old cowboys and farmers together, and the stories fly.”

Undated photo of artist James Castle. (Courtesy of James Castle Collection and Archive/Courtesy of James Castle Collection and Archive)

Scholars are concerned about something different — that Castle’s biography often overshadows his art. “In the excitement of discovery and the rush to make sense of the ineffable, we have, paradoxically, flooded Castle’s world with language,” writes Nicholas Bell, a senior curator at the Smithsonian American Art Museum, in the preface to the catalog for its exhibit “Untitled: The Art of James Castle.”

The 54 Castle works in the show, a 2013 Smithsonian acquisition, represent one of the largest collections of the artist’s work. The show’s prominence raises questions about how viewers should respond to self-taught art — which goes by aliases such as outsider, visionary, and folk art and involves figures such as Grandma Moses and Henri Rousseau. Can visitors be expected to ignore an artist’s biography, particularly in a field such as self-taught art, which suggests in its very title that context is vital?

Experts are divided on how museums should contextualize works such as Castle’s. On a panel at the American Art Museum in October, moderator Bell asked panelists what it would take for them to be satisfied that Castle had received due recognition. “To walk into the prints and drawings department at the British Museum and see his work alongside Jasper Johns or Rembrandt,” said Lynne Cooke, a senior curator at the National Gallery of Art.

“I’d like to see him make it into the American art history books and be understood as an artist who ranks among any that the country has ever seen,” echoed Leslie Umberger, curator of folk and self-taught art at the American Art Museum.

But Jeffrey Wolf, who wrote and directed the 2008 documentary “James Castle: Portrait of an Artist” which the American Art Museum will screen Dec. 1, can’t imagine a show that would have Rembrandt’s and Castle’s work hanging side by side.

“I think that people in this field have a chip on their shoulder about this kind of thing,” he says.

Johnson acknowledges that she was skeptical when another sister, who died six years ago, thought an ultimate Castle achievement would be his work earning a Smithsonian spot. “She would say that on numerous occasions, and I would say, ‘I hope you’re right. I hope that happens,’ ” Johnson says.

Johnson says she is “very, very thrilled” about the Smithsonian solo show. “I don’t know what we would expect after that,” she says. “That’s like a forever thing. It will always be there for people to see.”

Castle, according to Johnson, put the taught in self-taught. “He really was teaching himself,” she says. “He was trying to figure out why you look at a picture and the road goes off into the distance.” (Conservators, too, had to teach themselves new tricks to accommodate Castle’s treatment of the edges of his surfaces. It “blew their mind away,” Bell says.)

Innovative framing or not, the public almost didn’t get to see Castle’s work at several junctures. In two moves — from Garden Valley to Star, and then to Boise — Castle lost “everything he had made,” and “the entirety of Castle’s existing oeuvre was left behind,” Bell writes in the catalog.

Whatever the full extent of the lost troves of Castle drawings and paintings, the artist kept working, often reconstructing old landscapes and interiors from memory. Another serendipitous development helped propel him to national recognition. A nephew, Robert Beach, thought so highly of his uncle’s aesthetic promise that he shared the work with his art professors. They agreed, and gallery directors and curators followed.

It took Cousin Bobby’s recognizing the work, Johnson says, for her to understand that her uncle was an artist. “I realized that it might be more than just what Uncle Jim did,” she says.

As Castle’s aesthetic star has risen — including in a 2008 retrospective at the Philadelphia Museum of Art — so too have his sales, which is why Johnson and her sister find themselves silently thanking their uncle.

Bell, the Smithsonian curator, says he is not supposed to talk about specific numbers. But he points to one work in the show and estimates the gallery price tag for a work like it could be in the tens of thousands of dollars. “If you went and said you want to buy one of the constructions, you’d be talking significantly more,” he says.

“Since I got involved with Castle’s work, it’s probably gone up in value 20 to 30 percent,” says Wolf, the filmmaker. But, he cautions about Castle, “I don’t think there was a monetary component in his world at all.”

Not only was Castle a sweet person who never lost his innocence, Johnson says, but she also had occasion the summer she was 14 to see who was really caring for whom. When she invited friends — boys and girls — over for a party when her parents were away, Castle planted himself in a chair and made it known that no hanky-panky was to occur under his watch.

“We could see that the party was over; there wasn’t going to be a party. They got up and left,” Johnson says. “I thought, here mom was worried about who was going to stay with him, and he was keeping the teenager out of trouble.”

Wecker is a freelance writer.

Untitled: The Art of James Castle
The Smithsonian American Art Museum spotlights the work of an Idaho folk artist. Through Feb. 1, 2015. Smithsonian American Art Museum, Eighth and F streets NW, Washington, D.C. Visit americanart.si.edu/. 202-633-7970.