So you want to be the next Peggy Guggenheim. Besides wealth, what does it take to qualify as a heavyweight art collector today? Kelly Crow has answers on Lunch Break. Photo: André Klotz for The Wall Street Journal.

Last year, Brazilian collector Pedro Barbosa spotted a tumbling spiral made with hundreds of rubber tires at the Swiss fair Art Basel. The next day, Mr. Barbosa told a collector friend, Luiz Augusto Teixeira de Freitas, that he intended to buy the tires, actually a $150,000 installation by British artist Mike Nelson.

Surprised, Mr. Augusto reminded Mr. Barbosa that the artwork wouldn't fit inside Mr. Barbosa's São Paulo home. "Doesn't matter," Mr. Barbosa said. "I bet I can lend it to some museum in America." (For now, he is storing the work with a dealer in Italy).

It takes great wealth—and a little hubris—to ascend the ranks of the world's top art collectors. Mr. Barbosa, a 48-year-old former bond trader, is determined to qualify. Like many collectors of his generation, he began buying art on a whim just over a decade ago, but his pursuit has steadily grown serious. By collecting younger, hard-to-get Brazilian artists like Paulo Nazareth along with global superstars like Olafur Eliasson, he has earned a reputation as a highflying tastemaker on the international art scene. Mr. Barbosa employs a personal curator, Jacopo Crivelli Visconti, to manage his collection and allows guest curators to organize shows inside his spacious home in São Paulo's prestigious Jardins neighborhood. He also keeps an apartment around the corner where favored artists like Amalia Pica can stay to make and show their work. Friends say he is ever on the move, traveling to far-flung biennials and fairs from London to Istanbul to the United Arab Emirates. Altogether, his 500-piece collection amounts to roughly half his net worth, he said.

Mr. Barbosa is part of an emerging class of collectors springing up from all corners of the globe who are transforming the art marketplace with their willingness to splurge on art that suits their own tastes—not only the canons of New York or London. From Beijing to Bogotá, new art hubs are thriving in large part because these up-and-comers continue to amass art—in good economic times and bad. Many are investing heavily in contemporary art, the most speculative end of the spectrum, and changing the way the market functions.

Pedro Barbosa's Art Collection

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Pedro Barbosa has earned a reputation as a high-flying tastemaker on the international art scene by collecting younger, hard-to-get Brazilian artists like Jonathas de Andrade, shown here. This piece is titled 'Education for Adults' (2010). Jonathas de Andrade/Galeria Vermelho

A few generations ago, collectors like Henry Tate or Peggy Guggenheim needed aristocratic ties—or robber-baron-level fortunes—to ascend the ranks of the art world elite. Today, there are no rules for assembling a group of contemporary artworks that will one day prove iconic. Newcomer collectors say they pick up clues where they can. Some, like French investment banker Edouard Carmignac, have created art prizes to ferret out fresh discoveries—which they later showcase in their own art spaces. Others such as Roman entrepreneur Pierpaulo Barzan run foundations that mount traveling museum-style shows featuring artists they also happen to buy. Plenty more, like Costa Rican real-estate developer Judko Rosenstock, give pieces by hotshot artists to major museums like the Tate—moves that could bolster the cachet of his own pieces by those artists.

Mr. Barbosa's evolution is emblematic. Early on, he said he only collected artists from Brazil, but last year he decided to "go global," and he's been "going nuts" ever since—traveling to international fairs to collect artists like Germany's Wolfgang Tillmans and Lebanon's Rayyane Tabet. These additions serve to diversify his holdings, he said, but they also put his Brazilian pieces into a broader art context. To the same end, he also recently donated pieces by two young Brazilian artists, Jonathas de Andrade and Andre Komatsu, to London's Tate Modern.

It helps that his growing ambitions also coincide with his country's emergence as a global art hub. Until a few years ago, Brazil's art market was steady but relatively insular, anchored by South American collectors who were willing to pay as much as $50,000 for Lygia Clark's foldable aluminum sculptures or $15,000 for Beatriz Milhazes's flowery abstracts. But as Brazil's economy has expanded, local collectors have found themselves increasingly competing for their hometown favorites with buyers from around the globe—and prices have spiked as a result.

Even now as Brazil confronts higher inflation and signs of tapering growth, collectors keep bidding record sums for Brazilian modern and contemporary art. In May, Phillips in New York sold Ms. Clark's 1959 black-and white abstract, "Against Relief (Object No. 7)," for $2.2 million, the most ever paid for a work of Brazilian art.

                                  

Pedro Barbosa's collection includes 'Fine Tapestry' by Adriano Costa Adriano Costa/Mendes Wood DM, Sao Paulo

The auction record still represents a fraction of what China's counterpart collectors have paid lately for their own masterpieces, so market-watchers say Brazilian art still has plenty of room to grow, price-wise.

All this attention is pointing a bigger spotlight on the handful of Brazilian contemporary collectors who have positioned themselves as regional kingmakers, such as Mr. Barbosa. "The galleries look at everything Pedro is buying," said Mr. Freitas, the collector who saw the tires with him in Basel.

One of Mr. Barbosa's latest moves is telling. In September, he invited a curator from London's nonprofit Chisenhale Gallery, Polly Staple, to visit Brazil. He helped pay for her stay, and one morning he picked her up from her hotel for a tour of a few nonprofit art spaces and galleries. He had borrowed his wife Patricia Moraes ' black SUV for the occasion: "Welcome to an armored, bulletproof car," he said, chuckling, as Ms. Staple climbed in.

First up was Pivô, a nonprofit art incubator that opened last year in a former dentist's office inside architect Oscar Niemayer's undulating Copan building in downtown São Paulo. Next, they stopped by Galeria Vermelho—vermelho means "red" in Portuguese—to see a group show with artists like Cildo Meireles exploring issues of crime. The gallery had been robbed the week before, but the thief only took a CD player, so Vermelho didn't press charges. "The guy didn't think to steal the art," said dealer Akio Aoki.

An untitled work by Francesca Woodman Francesca Woodman/Mendes Wood DM, São Paulo

Mr. Barbosa also took Ms. Staple to meet Jaqueline Martins, a new dealer who specializes in selling São Paulo artists from the 1970s who have since been "overlooked" by the market, Mr. Barbosa said. Ms. Martins' roster includes Genilson Soares, a conceptual artist in his 70s who was once hailed for making large geometric installations often employing colored lighting and optical illusions. A few weeks after Mr. Barbosa's guided tour with Ms. Staple, Ms. Martins displayed one of Mr. Soares's oversize triangle works from 1973 at London's Frieze Art Fair—even though it wasn't technically for sale. "I bought that a month ago," Mr. Barbosa said. (He paid around $20,000.)

In São Paulo, Mr. Barbosa is well known for scouting Brazilian art schools and often buys pieces from promising students—a collecting tactic that's commonplace in New York but still relatively rare in São Paulo, dealers say. Local gallery Mendes Wood DM recently signed up one of his latest discoveries, sculptor Michael Dean. When Mr. Barbosa created an artist residency, one of the first artists he invited was Ms. Pica, another early find who just had her first U.S. solo museum show at the Museum of Contemporary Art in Chicago. Next up: New Yorkers Ken Okiishi and Nick Mauss.

Mr. Barbosa doesn't move through art circles with the panache of some of his countrymen, though. He is a millionaire, but he can't spend apace with Brazil's best-known collector, Bernardo Paz, a billionaire mining magnate from the Belo Horizonte region who reportedly spends $60 million a year commissioning and installing artworks throughout his vast jungle compound called Inhotim. Mr. Barbosa said he usually spends between $8,000 and $250,000 apiece on his art purchases. Still, he has found other ways to stand out.

A few weeks ago, Mr. Barbosa attended the opening party for the Mercosul Biennial in the southern Brazilian city of Porto Alegre. The event was held at the hilltop mansion of the biennial's president Patricia Fossati Druck, with partygoers like steel titan Jorge Gerdau Johannpeter dressed in designer suits. By contrast, Mr. Barbosa showed up wearing bluejeans, a baby-blue gingham shirt and Pac-Man cuff links. Shunning the glowing swimming pool and bar set up nearby to serve Brazil's favorite sugary cocktail, the caipirinha, Mr. Barbosa spent the night huddled on the lawn with artists like Mario Garcia Torres and Inhotim director Eungie Joo.

Ms. Joo mentioned her favorite piece in the biennial was a rusty landscape installation by Brazilian artist Cinthia Marcelle —at which point Mr. Barbosa leaned toward her and whispered, "I might have the best collection of Cinthia's work." Ms. Joo's eyes widened, and she grinned her approval.

Half of São Paulo's 40-odd contemporary-art galleries are less than five years old. Mr. Barbosa knows the strengths and weaknesses of their rosters better than anyone, said Buenos Aires collector Mauro Herlitzka. This market intelligence gives Mr. Barbosa's collection a competitive edge. But as Mr. Barbosa's collection takes in more artworks from beyond Brazil, his ancillary costs have also mounted. Because of Brazil's punishing import-tax laws, he must pay up to 50% above a foreign artwork's sale price just to bring it into his country—a markup he may not be able to recoup unless the art's value appreciates significantly over time. Dealers say some Brazilian collectors have found ways to avoid these import taxes by buying and storing pieces abroad or smuggling them into their luggage. Mr. Barbosa said he buys from the local SP-Arte fair, where taxes are typically discounted by the government. He said he also has proof he has paid the appropriate fees for everything displayed in his house.

Mr. Barbosa and his wife Patricia, who is head of investment banking for JP Morgan in Brazil, and their two children live in a cream-colored, two-story house on a leafy block in the wealthy São Paulo district of Jardins. Throughout their home, they have arranged a mix of sleek, geometric pieces by contemporary classics like Sérgio de Camargo and Jesús Rafael Soto alongside newer sculptures made from ordinary materials like hair curlers. In their backyard, a pair of conjoined shopping carts by Marcelo Cidade stands sentry beside the pool. On a bench in their living room sits a row of handbags that were dipped in concrete like candlesticks by Mr. Tabet, the artist from Lebanon. Even the walls of the children's bedrooms have been commandeered for art: "Sometimes my son complains, but I run a dictatorship," Mr. Barbosa said, grinning.

His own introduction to art was considerably less in-your-face. His father was a high-school gym teacher who only wanted his three children to get a solid education, which they did. Mr. Barbosa's first cousin was a major art dealer, Raquel Arnaud, but he said he rarely hung out in her gallery growing up—he preferred to hang out in nearby Ibirapuera Park and sell ballpoint pens to his friends for a profit. (He stuffed the clear pen cases with shredded currency to add cachet.) After he married in 1999 and settled into a life as a banker specializing in emerging markets and depressed bonds, he started buying art.

His first piece was a $20,000 Soto that he bought from his cousin, but he later switched to buying cheaper pieces by younger living artists, and he's largely stuck to that pattern ever since. When he finds an artist with potential, he tells them he likes to buy several works at a time, but he warns them he will likely stop collecting their work after they turn 40. He said he does this because it compels him to keep seeking fresh talent rather than pay ever-higher premiums for examples by artists he already owns.

Increasingly, Mr. Barbosa is looking farther afield for his art. The shift started in 2008 when he went to Frieze in London for the first time and marveled at how few collectors had turned up in the wake of the Lehman Bros. closure weeks earlier. Walking around the fair's vacant aisles, he realized he could ask galleries for steep discounts if he was willing to broaden the scope of his collection beyond Brazil. He took home pieces by Mr. Eliasson and Tomas Saraceno.

Last year, he ratcheted things up again by hiring his curator, Mr. Visconti, who has planned Brazil's pavilion for the Venice Biennale. Besides paying Mr. Visconti an undisclosed monthly retainer, Mr. Barbosa pays him to travel and inform him about artists to consider. The pair now invites young curators to mount shows of Mr. Barbosa's collection.

In a few more years, the plan is to publish a book about these shows—yet another way Mr. Barbosa hopes to lend lasting credibility to his collection. It's a tactic museums have been using for years, after all. "I don't want to spend too much on the parts," he said. "I'm more interested in the whole."

Write to Kelly Crow at kelly.crow@wsj.com

The Bass Museum of Art has received a $7.5 million grant from the city of Miami Beach, money the 50-year-old museum plans to use to expand educational and exhibition space.

As part of the expansion, the museum at 2100 Collins Ave. will build a new wing that includes two additional classrooms next to the existing Lindemann Family Creative Center. This will allow classes and events to be held at the same time. Exhibition space will be added in the spot where a switchback ramp now sits.

Construction on the new wing is expected to begin in April of 2015 and last a year. While the physical expansion will cost $7.5 million, the museum will raise additional money for educational programs and exhibitions.

E-mail: dwyer@nytimes.com

Twitter: @jimdwyernyt

Chanel Baldwin, exploring the Brooklyn Museum after learning that admission fees were “suggested.”

By ANAND GIRIDHARADAS

Published: August 22, 2013

CHANEL BALDWIN’S eyes sipped on that painting and only that painting, because it was what was available to her on this side of the money line.

On steaming afternoons for much of the season, Ms. Baldwin, who turned 16 on Thursday, parked herself after summer school at the Brooklyn Museum, a refugee seeking the asylum of air-conditioning.

Because she could not afford the $8 suggested student admission — one that she, like so many others, understood to be required — she never got further than the lobby. She helped herself to the bathroom and water fountain, though, and spent a lot of time gazing at the painting called “Napoleon Leading the Army Over the Alps,” by Kehinde Wiley. On Mondays and Tuesdays, when the museum was closed, she sometimes stood outside the glass doors that whispered puffs of cool air through their divide.

In a perfectly air-conditioned world, Ms. Baldwin’s art consumption might never have been. It was a boiling city that drove her into the frosty museum, and she’s not alone. In a city where culture is supposed to be king, New Yorkers in the summertime sometimes pop into a museum mostly to escape the heat. They come for the air but can grow to love the art, too.

Ms. Baldwin’s confinement to the lobby has made her something of an expert on that Napoleon painting — one of the few works hanging before the place where you pay. First she saw the obvious: A black man with Timberland boots had supplanted Napoleon in a riff on the famous painting by Jacques-Louis David. Then Ms. Baldwin saw the Starter brand wristband. Then she noticed the sperm cells swimming over the canvas. It made her wonder what the artist was trying to say about men of her race.

Ms. Baldwin could have remained at the school for chill air, but who wants to stay there a minute longer than you must? She could have gone home to her mother’s, not far away in Flatbush, but the miserly bedroom air-conditioners breathe too little into the living quarters. Here in the museum the air was different, almost lush. “It’s like when you’re getting into a pool, and they make you shower,” she said.

In the season now passing, museums in New York actively pursued people like Ms. Baldwin — potential visitors for whom liquid-cool air might have been a gateway drug to the art. On Twitter, where so many institutions speak more authentically than elsewhere, there were lures like “Beat the summer heat!” from @MuseumMileNYC, representing several institutions on Fifth Avenue. “Looking to beat the #NYC heat?” the Park Avenue Armory asked. “Beat the heat with our Store’s new Marilyn Minter water bottle & Jasper Johns beach towel,” the Guggenheim offered.

At the Museum of the Moving Image, in Queens, the chill seekers were easily detected: the ones with the soaking shirt backs, and those who sprinted in and asked the receptionist some variation of, “So what kind of museum you got here exactly?” During the heat wave, searing temperatures had driven most people from the surrounding streets, save for a crew of fluorescent-vested construction workers, belt deep in the chopped-up road, singing.

Over at the Metropolitan Museum of Art the next day, Nauman Shah, 25, was leaving French salon paintings on his way to Cypriot sculpture. For this Pakistani-born engineer, who works below earth on the Second Avenue subway project, the air-conditioning was especially important. He was observing Ramadan, the holy month of fasting for Muslims. He woke before dawn and gobbled breakfast, chased by four or five glasses of water — and then the fast. He had to conserve his hydration until 8:23 p.m. Ordinarily, he would have returned to bed, waking only for dinner. But a friend had persuaded him to go out, and they agreed on the Met over other activities, he said, in part because its cool air was almost as effective as sleep at forestalling thirst. It was aiding his monthlong quest, he said, to achieve “control over your soul and desires.”

Around this time, but in another wing, a bird, perhaps also fleeing the heat, fluttered overhead through Rooms 229 and 230. It jolted a teenage boy with a Germanic accent. He asked aloud, “Was that really a bird?”

Back at the Brooklyn Museum, Ms. Baldwin was hanging with Akeem Reuben, 16, her second cousin and another summer-school air-conditioning refugee. Ms. Baldwin was on her usual bench, where she perched because of her belief that it cost money to roam further. But the fee was only “suggested,” I told them. The cousins said no one had explained that before.

Next thing, the three of us were in line. When our turn came, I uttered the museum equivalent of “open sesame”: “No donation today, thank you.”

The gates parted. We received green tags to prove our bona fides. Ms. Baldwin and Mr. Reuben looked stunned: such a formidable barrier, so easily breached. Ms. Baldwin realized they had given her an extra admission tag. She made sure to return it.

Now what did the cousins want to see? “Statues,” Ms. Baldwin replied.

But she never made it there, because the first room set her alight and held her rapt until she had to leave. There was no label too tedious to read, no piece undeserving of her scrutiny. She couldn’t help touching some of the works.

“Look at the detail on it,” she said of a Fred Wilson mirror, gasping. Then over to a grid of shelves with dozens of jugs from around the world. Each column of jugs had a Rolodex-like set of descriptions. She and Mr. Reuben stood there and went through every last jug — reading the card, then looking up at the corresponding piece, then the next and the next. They had time.

A piece called “Avarice,” by Fernando Mastrangelo, gripped Ms. Baldwin. It appeared from afar like a classic Aztec sun stone. But she got up close. Traced her fingers over it. Went to one side, looked at it; went to the other side, considered it that way. She noticed that the piece was made of corn, and then detected a toothpaste tube, soda bottles and cowboy hats lurking on the surface, all crackling with meaning.

Watching her, I realized how the inadvertent exclusion from these rooms must have trained her eyes. Instead of cruising across many floors, she had stared at the Napoleon painting and a nearby sculpture until they had little to give. Having only them to consider had taught her how to see. Now her sight could be marshaled against anything.

But she was irritated with the museum. New York is run on the kinds of understandings that kept the cousins in the lobby, with so many places formally open to anyone but protected in their exclusivity by invisible psychic gates.

Ms. Baldwin suggested a more honest approach, since people tend to think you have to pay: “They should just put a sign out telling us that it’s somewhat free.” Either way, she pledged to inform all her friends.

As the cousins left the museum for the oven of the outdoors, two schoolmates crossed their path, heading inside. “What’s going on here?” one asked. It was the cousins’ first occasion to share their discovery.

In just the past few months Gordon VeneKlasen, a New York art dealer, flew to Hong Kong for that city’s first global art fair; gave a party for 50 at Harry’s Bar in Venice; installed an exhibition at his gallery in London; spent three days schmoozing American collectors in San Sebastián, Spain; and then jetted off to Switzerland for one of the biggest events of the art-world calendar, Art Basel.

Mr. VeneKlasen, 51, who has been a dealer in Manhattan for 25 years, recalls a simpler time, just a decade ago, when he could sit in his gallery on East 77th Street waiting for buyers to step through the door.

“It was a much gentler life,” he said. “You were in your gallery, and people came to you. The travel was for very special purposes, and it was not constant. Now, they have us marching.”

Globalization has come to the art market, and dealers are being forced out of their comfortable galleries in venerable art capitals like New York and London and jumping on a worldwide carousel of art fairs from Miami to Hong Kong to Basel to São Paulo.

By offering what a gallery cannot — seemingly endless gawking at artwork, artists and celebrities — the fairs are as popular, glamorous and fizzy as Cristal, attracting both the new moneyed classes that fly in from Kiev, Shanghai, Doha or Abu Dhabi and the serious American collectors who now prefer to do their browsing at fairs at home and abroad.

But their disruptive economics are not only shaking up dealers’ lives, they are also shaking up the art market, especially for galleries below the top tier.

While large galleries can — and do — pay the art fairs’ hefty fees and the cost of this globe-trotting existence, others find they are priced out or can’t compete. The ripple effects are starting to be felt in prime gallery districts like the Upper East Side and SoHo in New York.

“For a midsized gallery,” said Christopher D’Amelio, 47, a Manhattan dealer who closed his own gallery this year to become a partner at a larger one, “everything is a challenge.”

Large galleries with deep pockets are expanding their empires with new galleries in Beijing or Hong Kong. Yet fairs around the globe are, more and more, where the art world does business.

Dealers worldwide earned about 36 percent of their sales on average through local or international art fairs in 2012, an increase of 6 percentage points from 2010, according to the European Fine Art Foundation’s Art Market Report by Arts Economics, which surveyed 6,000 dealers.

For some, the share is even higher: according to Mr. VeneKlasen, 75 percent of his sales 10 years ago were made in his galleries, but now nearly two-thirds of revenues are earned on the road.

The Arts Economics report said that some dealers attended up to 10 fairs a year.

“In the early ’70s there were four major art fairs; in the 1990s, 50; and suddenly now there are 180,” said Linda Blumberg, executive director of the Art Dealers Association of America, who spoke this year after returning from Art Basel. “Some of the dealers I had met in Basel, it was crazy. They had been to Hong Kong, then Venice, then Berlin and London. It is hard to think in the 12-month calendar of any month when there is not an art fair. It is pretty intense.”

Some galleries showing younger, more contemporary artists can still attract people from the street, and attendance is up, gallery owners say. But for more established artists, with more expensive work, dealers have to go where the customers are. According to the Web site artvista.de, which tracks art fairs, about 10 million people visited art fairs or other events like the Venice Biennale in 2011.

One longtime art collector, Howard Rachofsky of Dallas, used to buy his art mainly in New York, but in the past year has traveled to fairs in Basel, New York and London.

“You want to see art, and you want to see the people behind it, get to know the gallerists and, ultimately, the artists, and the easiest and most efficient way of doing this is at an art fair,” Mr. Rachofsky said.

“It is really about networking and seeing an art gallerist from Düsseldorf and a gallerist from Madrid 50 feet from each other, and getting a chance to spend a few quality minutes with each one of them,” he added. “That is the reason we go.”

For dealers, the life takes a lot of planning, and it is expensive. Galleries must build inventory to take on the road, and ship it, produce catalogs and send installers ahead to prepare the art fair stand, which becomes their temporary but important face to the world. Mr. VeneKlasen, for example, this year hired an emerging visual artist, Aaron Curry, to design his booth in Hong Kong, shipping hundreds of silk-screen panels from Los Angeles. Some big New York galleries then send as many as 20 employees to staff the fairs; travel, hotels and parties for collectors, as well as insurance and installation for the art, can push the cost past $300,000 for one fair alone.

“We used to sit around in the gallery on a Saturday afternoon hoping someone would come in,” said Arne Glimcher, of the Pace Gallery in New York. “What we are dealing with now is destination shopping. We have to be in different places. We bring the art to the collector rather than bringing the collector to the art.”

Some dealers only reluctantly take part. Paula Cooper, the New York art dealer, attends some fairs because they allow her to see work from numerous countries in one place. But mostly she sends others from her gallery, decrying the loss of what she describes as a more thoughtful time even just five years ago when she could sit with artists and collectors and talk about art. “It is just like any business in the world now,” she said. “It is becoming a global enterprise.”

Mr. Glimcher, too, said he preferred others from his gallery to make the global trek.

“Fairs are beneath the dignity of art,” he said. “To stand there in a booth and hawk your wares — it is just not how you sell art.”

The fairs also have an impact on artists, who are producing work according to the demands of the art fair calendar rather than their own creative rhythms.

Not everyone can play this game. While some smaller dealers get better exposure by showing alongside bigger galleries at fairs, many struggle even to get past the long waiting lists for entrance into the fairs, while those that win access must work hard to recoup the costs, including the booth fee, airfares, hotels and entertainment. Just a booth can start at $15,000, go to $40,000 or so for a midsize gallery, or even $100,000 and above for a larger space. Marc Spiegler, director of Art Basel, said the fairs are not just for dealers, but have become a melting pot where everyone in the art world can connect.

“Now you see every curator and museum director going to the fair, and artists, too,” he said. Art Basel attracted about 86,000 visitors to Switzerland over six days in June.

In this environment many of the biggest galleries at the top end of the market are thriving, but those at the bottom are contracting. The Arts Economics report found that sales by dealers with annual revenue of less than 500,000 euros fell 17 percent in 2012, whereas sales for dealers with annual revenue exceeding 10 million euros rose 55 percent. Worldwide, the top one-tenth of dealers account for more than 60 percent of total gallery sales above 20 billion euros.

This harsh economics is reflected in New York’s art districts, and while a few galleries are adding space or opening in neighborhoods like the Lower East Side and Bushwick, Brooklyn, others are faltering, brought low by a host of pressures that include rising rents, competing Web sales and the incursion of big auction houses, which are trying to sell more art through one-to-one sales.

According to the Web site Galleries of New York, which collates real estate data, the number of galleries in the big art districts has declined in the past few years — galleries in West Chelsea have fallen to 282 from a peak of 364 in 2007; those in SoHo have dropped to 87 from 337 in 1995.

Mr. D’Amelio ran his own gallery with a business partner on West 22nd Street in Chelsea since 1996, surviving the terrorist attacks on New York and the most recent recession. He said there was still a place for midsize galleries like his had been. But he closed his gallery in January and became a partner at David Zwirner, one of the prestigious larger galleries that offers the business resources — a staff of back-office assistants, public relations officials, a high-quality Web site and brand recognition — necessary to function in this newly global marketplace, namely the ability to lure the best artists and take their work to the richest buyers.

“It is completely international,” said Mr. D’Amelio, who will attend Expo Chicago next month as the circuit starts up again after the summer. Dealers must travel to get to know the wealthiest art buyers in the market at any time, he said. “If you don’t, then your artists will leave you for a gallery that does.”

The anonymous gas station operator whose shop walls were graced with a Banksy mural, which he subsequently cut out and put up for auction, has decided to come forward.

Eytan Rosenberg, 44, owned the garage on the corner of Beverly Boulevard and La Brea Avenue in Los Angeles with his family, including his father, Josh Rosenberg, and his sister Ronit Karben. In 2008, he was approached by a regular customer, Thierry Guetta, better known as the street artist Mr. Brainwash, who asked permission for a friend to paint on the walls.

“He didn’t say Banksy,” Mr. Rosenberg said in a phone interview late on Thursday afternoon. “He wasn’t trying to sell me on it, and he didn’t try to hype it at all.”

He wouldn’t have known who Banksy was, anyway; the pseudonymous British artist was just gaining international acclaim. Still, he gave his permission for the painting to happen. It was stealthy.

“I think he came at 4 a.m.,” Mr. Rosenberg recalled. He checked his security feed for evidence of the elusive artist after seeing the piece the next day. “I went right to my cameras, and they were completely blank,” he said. His tech specialists were stumped: another Banksy mystery.

The mural, “Flower Girl,” showing a girl peering up at a security camera sprouting out of a stock, remained a source of local fascination for years, along with a similar piece on a wall at an adjoining car wash. “Garden Girl” depicts a girl with a watering can looking over a stem sprouting an antenna. That piece remains.

Once Banksy put up his stencils, “there was never any mention of what would happen subsequently” to them, said Michael Doyle, the consignment director at Julien’s Auctions, which is handling the sale of “Flower Girl.” “I’m assuming that was not really one of Banksy’s concerns at the time.” (A spokesperson for Banksy did not comment.)

After Josh Rosenberg died in 2009, Mr. Rosenberg and his family decided to sell the business; a Chevron franchisee bought it in 2012.

“I said, ‘I’ll sell you the location, but I’m going to take the Banksy,’” Mr. Rosenberg recalled. He worried that if he didn’t cut it out, it would be demolished or painted over. So he spent around $80,000 to remove “Flower Girl” and repair the wall. “It was almost like a family heirloom at that point,” he said.

Nonetheless, he decided to part with it. “I would love to be able to keep it, but it’s owned by me and my sister,” he said. “It’s a large piece, and I’m not an art collector, and I really don’t know what to do with the piece.”

He does, however, have plans for the proceeds, which will be split with his sister. “This thing I see as a gift from God, or whatever higher power,” he said. “I’m not going to be greedy, I’m not going to be stingy. I plan to use the proceeds that I have to do other beneficial things – push it forward, or whatever that term is. Let the good energy continue.”