Often referred to as the “head,” the half- to one-inch layer of thick foam on top of a beer is the first sign of a well-poured pint. “Aesthetically, foam makes a beer just look more inviting,” Greenpoint Beer & Ale Co. head brewer Mike Nika states in an email. “A beer sans head looks lifeless and makes me anticipate being disappointed by whatever I’ve ordered.”

Beyond visual appeal, the head provides a variety of benefits. It influences the aromatic experience and adds an enjoyable texture to the brew. As drinkers sip from a foamy pint, the beer’s aromas unfold as the bubbles dissipate.

Tight, uniform microbubbles are the sign of high-quality brewing, Nika says. If the foam is too large and sudsy, it might be a sign that the carbonation process was rushed or the beer was under-carbonated.

Get the latest in beer, wine, and cocktail culture sent straight to your inbox.

Greenpoint Beer employs a “low and slow” method of force carbonating beer, wherein carbon dioxide is slowly added to the beer over the course of several days, creating a tight foam that floats atop the beer for longer.

Beyond production methods, the style of beer also influences the look, texture, and retention of a beer’s foam. Barley and wheat-based beers produce more natural carbonation during fermentation, while those with corn additives can easily fall flat. Nitro beers stand tall above all others, with especially pronounced heads.

Guinness, for example, is carbonated primarily with nitrogen, which when poured properly, results in a wonderfully creamy and cascading foam,” he says. “Unlike in a traditional beer, the nitrogen escapes the beer very quickly and it is prone to tasting flat unless consumed quickly. Being served Guinness without foam is a crime, if you ask me.”

If a pour lacks this signature head, are bar-goers within their rights to send back the pint? Nika says yes, it’s fine to query any issues regarding the presentation of a drink, including dirty glassware or substandard foam.

If a bar doesn’t have a craft beer focus, though, he says the safest bet is to simply order a can or bottle to avoid disappointment.