Still wet, the signature artwork was photographed for the clients of Michael Reid Contemporary Art Gallery that same day.

By 8.30am on Wednesday, the day of the opening night of the third edition of Sydney Contemporary, an international four-day art fair featuring 500 artists, the painting by the former National Art School graduate had been sold.

The artist's remaining paintings were snapped up that night, including a $16,000 coffee table, a homage to Yves Klein.

Twice Archibald Prize finalist Marc Etherington sold so well Michael Reid director William Sturrock took all but one of his 24 fish tank paintings down from the walls.

Buyers had come as far afield as Singapore, Hong Kong, London and New York.

By day three of Sydney Contemporary, art collectors and VIPs had largely made way for the general public, first timers and new collectors.

Children were entranced with the Red Room, an art therapy installation by Japanese-Australian artist Hiromi Tango, and an educational program of public talks and tours were well attended.

Art fairs are growing in popularity worldwide as a more social, less intimidating way for art lovers to browse art.

"Every time an art gallery shuts you've got 15 to 20 artists who don't have a shop front," said collector and Sydney Contemporary board member Sue Cato. "So fairs are like a heart starter to the gallery."

This year, collectors seemed to be chasing paintings more than video art.

"To have video art you have to have all the hardware that goes with it," Ms Cato said. "It's much easier for people to acquire sculpture or flat art, paintings, and have it on a wall and love it and live with it."

In a year of Brexit, Trump and debate around Australia Day celebrations, more political challenging subjects could be found in the art of Tony Albert, Vincent Namatjira and Paul Ryan, and less directly but no less passionately in that of Joanna Braithwaite's polar bear stranded on ice.

Justin Miller, dealer and founder of Justin Miller Fine Art, estimated he had sold $1 million worth of paintings, including seven smaller works by Brett Whiteley. An ink on paper self portrait went to the National Gallery of Australia.

Acquisitions by the major galleries are much sought after and the NGA's director Gerard Vaughan and Art Gallery of NSW director Michael Brand were both spotted familiarising themselves with new gallery works produced specially for the fair.

This year's Sulman, Wynne and Archibald Prize winners and finalists Guy Maestri, Nicholas Harding, Joan Ross and Lucy Culliton were represented alongside young artists such as Juz Kitson and Richard Lewers.

All editions of Maternal Line, Justine Varga's controversial winning entry to the Olive Cotton awards, had sold out by Friday.

Miller was quietly confident he had secured a buyer for one of this year's most expensive artworks, a white marble Botero sculpture with a sale price of $575,000, from South America's most famous living sculptor.

Michael Parekowhai's Coral, a life size doll made of polished steel, had an asking price of $NZ210,000 ($189,000) at Roslyn Oxley9 Gallery, and an interested buyer.

Art Money offered interest-free loans for artwork purchases that could be taken home and paid off in instalments.

A third of applicants at the fair were first-time collectors acquiring small works for less than $5000, mostly for the home wall, founder Paul Becker said.

Most new collectors were "creatively interested" people, often lawyers, doctors, marketers, even journalists, Mr Becker said.

Big collectors often bought works they knew were coming in, said Ms Cato said, "but equally a gallery is always interested in new and passionate people".

"Our philosophy is you can't tell who is a collector and who is not," said Marielle Soni, director of Alcaston Gallery, which sold out of the works by two Indigenous female artists. "Don't make assumptions, collectors don't wear a uniform."