Art Basel, which closed on Sunday, effectively rounds off the art market’s annual program of fairs, sales and exhibitions. Coming after auctions in New York that clocked sales totals less than half of those a year earlier, art dealers have been cheered by apparently buoyant sales at the fair.

Dealers ticked off the highlights: a Sigmar Polke for €6.5m (£5.1m) at David Zwirner and Paul McCarthy’s Tomato Head (Green) (1994) sold by Hauser & Wirth for $4.75m (£3.3m) and a Mike Kelley Reconstructed History for $1.5m. The availability of such works suggested that dealers are getting more of the best work coming up for sale now that the auction houses have stepped back from offering seller’s guarantees.

But whether these headline sales, like the auctions, are a gloss that disguises other weaknesses, is not yet clear. The art market has been going through a testing period, not least its sensitivity to fluctuations in the global economy and the uncertain political outlook.

But the one story that might have been expected to affect art market confidence – the civil suit against the directors of the Knoedler & Company gallery in New York earlier this year, appears to have had scarcely had any impact.

Back in February, jurors heard how the gallery – one of the most prestigious – had passed off literally dozens of fakes said to be by abstract expressionist masters including Mark Rothko and Jackson Pollock to unwitting collectors. The case was settled before Knoedler’s directors, Anne Kennedy and Michael Hammer, were called to testify but not before the court heard how collectors Domenico and Eleanore De Sole had been swindled.

In total, the gallery sold upwards of 70 fakes to collectors who were readily – and understandably – willing to trust the provenance of the works offered by the gallery. “A case like this tends to wake people up,” Jason Hernandez, the lead prosecutor in the criminal investigation, told Artnet. “It touched such a well-known gallery in addition to how much money was involved.”

But the case also hinted at another issue: just how few artists’ estates now have functioning authentication boards. In 2011, following a lawsuit brought by the British collector Joe Simon-Whelan against the Andy Warhol Art Authentication Board over its refusal to authenticate a self-portrait of the artist that Simon-Whelan had purchased for less than $200,000 in 1989, the Warhol Foundation closed down the service.

But that was not the Warhol Foundation’s only problem with provenance. Dozens of Brillo boxes it had authenticated over the years had to be “reclassified” as posthumous works.

Other authentication boards soon closed up: Keith Haring, Roy Lichtenstein, Jean-Michel Basquiat. The cost of defending cases (the Simon-Whelan case had cost the Warhol estate $7m) and the threat of further lawsuits over issues of liability had made such services too risky to maintain, each said.

One of those to benefit is Richard Polsky, an art dealer, author and Warhol expert who is now running an authentication service, Richard Polsky Art Authentication. He told the Guardian recently that the Knoedler fraud trial “had no effect because it was an isolated incident in terms of the scale of what happened. There were so many red flags. It was unbelieveable. That’s why it had no effect. It gave dealers something to talk about, and it was a lot of fun, but I don’t know anyone who thought it made any sense on any level.”

“That’s not to say that things don’t happen on a daily basis that aren’t always kosher, but that was one of the most unusual cases I or anyone has seen.”

It was unusual, he says, because the intent to pass the fakes off was so clearly fraudulent. Sixty percent of the art that Polsky is asked to authenticate is fake. But they are fakes without fraudulent intent. “There’s a huge difference between fraud with the intent to make money and, ‘Oh, I love Basquiat. I’m going to make my own’, and somehow that reaches the market.”

The motivation for faking art is sometimes hard to figure out, Polsky says.

“Someone called me from North Carolina saying they’d found a carving of a cat with Warhol written on the bottom of it. Then they said they found a Picasso in the same market. I laughed, of course, but the point is, what was the intent? Maybe the guy that made the cat was doing it for fun, got bored, and put it in a market.”

Part of the reason that the Warhol Foundation was so detested by collectors was that it didn’t just refuse to authenticate certain works, it refused to authenticate, then stamped “denied” on the back, and refused to offer any explanation for their decision.

“The Warhol people had you sign a disclaimer stating that if they found the work to be inauthentic they were allowed to stamp the work on the back. Obviously, if they did that you’d be bummed out. But if you asked them why, they wouldn’t give you a reason. They’d say something like, ‘We don’t want to aid counterfeiters.’ So now you’d not only be bummed out but mad!”

His policy, he says, is complete transparency. The service costs $2,500 for a painting, $1,500 for a drawing and $1,000 for a print. “You get a letter explaining why, or why not, I think it’s authentic or inauthentic.” There’s a legal disclaimer, of course, but at least – unlike a multimillion-dollar art estate, he’s not worth suing.

For the most part, the business of authentication is determining what makes sense. Warhol, clearly, directed his studio to make works for him and he was, to some degree, almost cavalier over what he chose to sign. Provenance, as the plaintiffs in the Knoedler scandal found out to their cost and embarrassment, is key.

“If someone comes to me saying they inherited a Warhol from their mother who’d bought it from a gallery in Cleveland in the 60s it’s fairly easy to determine that there were no galleries in Cleveland in the 60s that showed Warhol. But it’s a great feeling when something checks out.”

But that’s not to say that frauds are not taking place daily. A scandal over faked 18th-century French furniture, with two specialists under investigation for the alleged making and sale of counterfeit chairs for as much as $1m each, some of which were bought by Versailles, is currently making headlines in France.

Polsky says that though this art market has been in a boom far longer than anyone anticipated, that does not necessarily translate into a greater opportunity for fakery. In part, that’s because the manufacturing involved in many artists’ work is simply too difficult, and too expensive, to duplicate. “You can’t fake a Jeff Koons – it would cost too much to manufacture.” The temptation to fake may be greater, but the more valuable art becomes, the more scrupulous – usually – people become about buying it, he says. “As the saying goes, if it’s too good to be true it probably is. If you’ve got a Damien Hirst butterfly painting show me something. A letter from White Cube or Gagosian. Or where did the butterflies come from?”

In those types of cases, authentication is relatively straightforward. But things can always get complicated. Polsky recalls a case in which Keith Haring’s estate refused to approve graffiti the artist had made in the New York subway. The work was real but the estate claimed the artist had not intended the work to reach the market.

“So it’s all about intent. Did Haring intend these things to be works of art? The answer is yes, he did. Whether he intended them to enter the market is not my concern. My concern is: are these real, did Haring intend for them to be real?”

The opposite is true in the case of Willem de Kooning’s toilet seat. The artist was living in the Hamptons when he took some paints to the outhouse and painted the toilet seat. Years later, someone tried to sell it. “I would turn that down,” says Polsky. “Did De Kooning paint it? Yes. Did he intend it to be a work of art? No. That’s how the authentication works – what was the artist’s intent?”

“It’s true today and it was true 30 years ago,” says Tom Freudenheim, the former director of the Baltimore Museum of Art. “It was easier to raise money for naming somebody’s building than paying someone’s staff.”

The party’s over as New York’s top museums feel the pinchMoMA, the Met and the Brooklyn Museum are planning to reduce staff numbers to help balance the books theartnewspaper.com

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Artsy continues its domination of the online art marketplace with the launch of new software that will allow collectors to bid in live sales at Phillips and Koller auction houses.

Artsy partners with Phillips and Koller auction houses on live biddingNew technology allows collectors to take part in sales in real time theartnewspaper.com

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Three leading employees at the Metropolitan Museum of Art have stepped down as part of efforts to close the museum’s $10 million deficit. [The New York Times]

The board at the Pensacola Museum of Art has gifted the museum to the University of West Florida. [Pensacola News Journal]

HISTORY

“The civil suit against the directors of the Knoedler & Company gallery in New York earlier this year appears to have had scarcely had any impact [on the art market].” [The Guardian]

Kurt Cobain’s art will be shown to the public in an upcoming traveling exhibition. [The New York Times]

A roundtable on the origins of the National Gallery of Art in Washington, D.C. [NPR]

Art Changes: Celia Hempton