Beer drinkers are choosy about foam on their beverage, and getting the foam right is an important selling point for brewers, according to Charles Bamforth, Anheuser-Busch professor of brewing science at the University of California, Davis. "There's no question foam is important to consumers, but what are the attributes that make it important?" said Bamforth. To find out what drinkers like about foam, Bamforth showed over 300 beer drinkers in the U.S., Germany, England and Japan photographs of glasses of beer poured with different heads of foam. Then they filled out questionnaires on what they thought of the beer. Most of the interviewees expected that beer with good foam would "taste better" than a flat-looking beer, even in the U.S. where beer is often drunk straight from the bottle or can. Some thought that the beer with good foam actually looked colder, or was darker in color. Draining a glass of beer sometimes leaves a lacy pattern of foam behind. Some drinkers thought lacing meant a clean glass, while others thought it meant the glass was dirty. In fact, lacing has nothing to do with the glass, said Bamforth. Lacing happens when the bitter-tasting compounds from hops link proteins in beer together. Brewers can control lacing by changing the hop extract that they use for brewing. The survey results were published in the Journal of the Institute of Brewing.