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.