COLOGNE, Germany — If the market for contemporary art is in danger of overheating, the first canary in the coal mine will surely be those fashionable young artists whose prices have been driven up by speculators over the past few years.

Midseason auctions of affordable works by emerging names are telling temperature gauges for the contemporary market. Phillips’s quarterly “Under the Influence” sales have, in particular, become events where benchmark values are set for works by young artists. Many of these artworks are privately bought and then quickly sold on, or “flipped,” by insiders before a wider audience gets to hear about them.

The 202-lot sale at Phillips in London on April 8, which included recent paintings by Parker Ito, Dan Rees, Lucien Smith, Oscar Murillo and other flippers’ favorites, totaled 1.6 million pounds, or $2.7 million, which was above the low estimate. Two-thirds of the material found buyers, with all the headline lots successful.

The top price was £56,250 paid by a telephone bidder for a 2012 “Artex Painting” by the Welsh artist Mr. Rees (born 1982), valued at £20,000 to £30,000. The work is one from a series of colorful abstracts made with household ceiling coating, and it proved to be the most expensive of four such works that have come on the auction market in the past eight months.