Left: A gilt bronze figure of Amitaryus from the Qing Dynasty; right: A bronze ritual wine vessel of the late Shang Dynasty.

"Consignors (sellers) and buyers are experienced players in the market. They will compare the possible price fetched at auction with the price they can bargain for at private sales. People also pay a buyer's premium for private sales, which isn't much lower than that of auctions."

He says Asia ranks third after Europe and the United States in private sales volume, and the Chinese mainland ranks at the bottom in Asia.

"Private sales in Asia will increase, but at a slow speed. It relates to the market's maturity."

Mainland buyers make up 30 to 40 percent of Sotheby's Hong Kong customers. But they are not so familiar with private sales compared with other Asian buyers, Ching says.

Whether they will embrace this form of transaction depends on their confidence in and knowledge of the item they purchase, he adds.

"Some buyers are more confident of an open platform, where they can track other bidders and the prices they offer. These are invisible in private sales."

Auction houses are also opening galleries and organizing exhibitions and lectures to improve private sales, which is not one of their traditional working practices. Poly Auction Hong Kong, for example, will open an art center one day before its spring sales.

"We have to meet clients' changing demands," says Alex Chang, Poly Auction Hong Kong's managing director.

"But regarding the level of service, we still differentiate with galleries. Auction houses mainly focus on established artists with a market, while galleries discover and market new talents."

Professor Gong also says there is a clear trend for more private sales, which provide a shortcut for sales and brings in cash while reducing risks. "Auction houses are gradually establishing a monopoly of the art market."

Contact the writer at linqi@chinadaily.com.cn.