Judging a beer's head by foam height, lacing and retention

Why the head matters

When you pour a beer, carbon dioxide comes out of solution and forms bubbles. Proteins from the malt and bitter compounds from the hops coat those bubbles and hold them together. That coating is what turns fizz into foam.

A good head does three things. It releases aroma right under your nose as the bubbles burst. It gives the first sip a soft, creamy texture. And it protects the beer a little from the air. A beer with no head looks tired before you taste it. Often it is. Our guide to beer foam science explains the chemistry in more depth.

Foam height: what is normal

For most beers, a head of around two to three fingers in a standard glass right after pouring is a good target, roughly 2 to 4 cm. German wheat beers and Belgian ales are poured with tall, dense heads. Some English cask ales are served with a thin, tight head. Very strong beers often have little head because high alcohol works against foam.

Height depends heavily on the pour. A beer poured slowly down the side of a tilted glass will have less head than one poured straight down the middle. So before you blame the beer for a flat appearance, check how it was poured. Our guide to how to pour beer covers the technique.

Bubble size and texture

Look closely at the foam. Fine, tight bubbles that look like whipped cream or meringue usually mean good foam proteins and proper carbonation. Large, soapy bubbles that pop quickly suggest weak foam, a dirty glass or a beer that has been over-carbonated and is releasing gas too fast.

Colour matters too. Pale beers usually carry a white head. Darker beers have off-white, tan or brown foam. A head that looks grey or patchy can point to a glass that was not properly rinsed.

Retention: how long the head lasts

Retention is how long the head stays before collapsing. Watch it over a few minutes. In a well-made beer in a clean glass, a head should hold for at least a couple of minutes and leave a thin layer on the surface for much longer.

Breweries measure this precisely. A common laboratory method, the NIBEM test, times how long foam takes to collapse by a set distance in a standard glass. Values are given in seconds. You do not need the instrument at home. Just notice whether the head vanishes in under a minute or lingers while you drink.

Poor retention has several common causes:

• Fat or oil. Lipstick, food on your fingers or a greasy glass destroys foam almost instantly. Fried snacks at the bar are a common culprit.
• Detergent residue. A glass washed with soap but not well rinsed kills foam.
• Brewing choices. Too little foam-positive protein, high levels of adjuncts like rice in some light lagers or certain processing steps can all reduce retention.
• Age and warmth. Old beer, or beer stored warm, often loses foam stability.

Lacing: the rings left behind

Lacing, sometimes called Brussels lace, is the pattern of foam left clinging to the inside of the glass as you drink. Good lacing forms rings at each sip level, like the lines on a tree trunk. It shows that the beer's foam proteins are sticking to a clean glass.

Lacing is a joint score for beer and glass. A beer with excellent foam will leave no lace on a glass with a film of grease or rinse aid on it. If you see bubbles clinging to the sides of the glass below the surface, the glass is dirty. A properly clean glass, sometimes called beer-clean, lets bubbles rise freely from the bottom and leaves no bubbles stuck to the walls.

Judging the head at home or in a bar

Use a clean, rinsed glass. Rinse it in cold water just before pouring so it is wet and cool. Avoid glasses that have been through a dishwasher with rinse aid. Our guide to beer glassware explains which shapes suit which styles.

Pour with a steady, moderate stream. Then score four things: initial height, bubble texture, how long the head lasts and the lacing left behind. A simple note like "two fingers, tight white foam, good retention, steady lacing" is how judges write it.

If the same beer has a great head at one bar and none at another, it is probably the glass or the pour, not the beer. Learning to tell foam problems from beer problems is part of the foundation of sensory training.