GENEVA • There is an art to how dealers display prized works.
So when thousands of wealthy collectors descend on Switzerland for Art Basel this week, works by some of the most coveted artists will not be on public display.
Instead, they will be offered to select clients, one by one, in private viewing rooms.
Some rooms are above the aisles of the convention centre, where 290 galleries from 34 countries will set up booths at the world's biggest modern and contemporary art fair.
Others are sequestered at high-security warehouses in an industrial area 15 minutes away by car.
"I call it an off-the-floor trade," said Mr Larry Wasser, a Toronto collector and former wealth manager.
"These transactions are happening every day during the fair. It's all about putting buyers and sellers together during the Super Bowl week of the art business."
Art Basel's 50th edition will have an estimated US$4 billion (S$5.45 billion) of art on display, according to insurer AXA. While galleries ship scores of works, their carefully curated booths can accommodate only a fraction of the inventory.
Private viewing rooms, which Art Basel rents to exhibitors, offer flexibility to galleries and discretion to buyers and sellers.
"You plan it very carefully," said Mr Marc Glimcher, president of Pace, a leading international gallery. "It's not like you put a bunch of things in a private room and hope for the best."
Demand for private rooms is on the rise, according to organisers of the fair, which drew almost 100,000 people last year. The 12 showrooms at this year's event can be reserved hourly, daily or for the entire week.
The rent can be up to US$3,000 for a two-hour slot.
Works are often shown privately because owners do not want everyone to know they are parting with a prized Andy Warhol or Mark Rothko. And some buyers do not want to be seen splurging on art.
"A lot of people like the idea of looking at the work of art without other people looking at them," said art adviser Abigail Asher.
This year's fair includes a heart sculpture by Jeff Koons, an early conceptual painting by John Baldessari with a US$8-million price tag and Pablo Picasso's portrait of his son for US$7 million.
Galleries have used private viewing spaces at art fairs for years.
But as paintings and sculptures have grown in size and value - and the cost of exhibiting at fairs has surged - small storage closets in booths no longer suffice.
Mr Fritz Dietl, whose logistics company shipped enough art to Basel this year to fill three jumbo jets, recalled the days when dealers visited storage rooms with clients, took an artwork from the crate and showed it leaning against the wall.
"It didn't cost anything," he said. "Then the fair got smarter."
Some exhibitors, like Galerie Gmurzynska, are building private viewing rooms within their booths.
That allows clients to look at art without "everyone breathing down their neck", said chief executive Mathias Rastorfer.
"If you are an important collector, it's very difficult to peacefully walk around and look" at Art Basel.
"It's become very aggressive."
For dealers who are not showing at the fair, off-site warehouses offer a way to take advantage of the Art Basel moment on their own terms.
"When people are coming to Basel, they are in a money-spending mood," said Mr Jeremy Larner, a New York art dealer.
Two years ago, he sold a US$5-million painting out of an Airbnb facility during Art Basel. This week, he is renting a viewing room at a warehouse to showcase four paintings by Rudolf Stingel, an artist with a current retrospective at Basel's prestigious Beyeler Foundation.
"This is the time to do it," Mr Larner said. "It's one thing to show someone something on an iPad, but showing it in the flesh is so much better."