Head size on a pint and why a little foam is a good thing

Where foam comes from

Beer foam is carbon dioxide bubbles wrapped in a thin film of proteins from the malt and bitter compounds from the hops. Those proteins and hop compounds gather at the surface of each bubble and hold it together. That is why a well made beer can keep a firm head for several minutes while a glass of soda water loses its fizz in seconds.

How much foam a beer can make depends on the recipe. Wheat beers, rich in protein, foam hugely. Beers brewed with a large share of rice or sugar have less protein and often make thinner heads. How long the foam lasts depends on the beer, the pour and the glass.

Foam carries the aroma

Much of what we call flavour is smell. As bubbles rise and burst at the top of the glass, they throw tiny droplets and aroma compounds into the air right under your nose. A beer with a lively head delivers more of its hop, malt and yeast aroma with every sip.

A beer poured with no head sends that aroma off into the room instead. The first sniff is weaker and the beer tastes flatter, even when it is perfectly fresh. For aromatic styles like IPA, wheat beer and Belgian ales, a good head makes a large difference.

Foam changes the first sip

Drinking through a layer of fine foam softens the first impression. The beer reaches your tongue through a creamy cap, so it feels rounder and less prickly. Foam also holds some of the bitter hop compounds, which is why the top of a head can taste a little more bitter than the beer underneath.

A firm head also slows the escape of carbon dioxide from the beer beneath. That keeps the beer livelier for longer. In a Czech pub this is taken to an art, with pours that are mostly foam. Our guide to Czech lager pours shows how far the idea goes.

How much is right

For most beers, a head of about two fingers, roughly 2 to 3 cm, is a good target. German wheat beers and Belgian ales often carry more, three or four fingers. British cask bitter, especially in the south of England, is often served with very little.

Measure and foam do not have to fight. In Britain some pubs use oversized lined glasses, with a line marking the full measure and room above it for the head. German glasses carry a fill line too. If you are worried about short measure, look for the line rather than refusing the foam.

What the head tells you about the bar

The head is a quick quality check. Pour a fresh beer into a beer clean glass and you should see a firm head, fine bubbles rising from the bottom of the glass and rings of lace left on the sides as you drink.

• Head collapses within a minute: often a greasy or soapy glass.
• Bubbles clinging to the sides: residue on the glass.
• Huge, loose, soapy head that will not settle: warm beer, wrong gas pressure or a rushed pour.
• No head at all on a beer that should have one: flat beer, a dirty glass or old stock.

Our guide to judging a beer's head goes deeper into lacing and retention.

How to pour for the right head

A good head starts with the pour. Rinse a clean glass with cold water. Hold it at about 45 degrees and pour down the side until it is about two thirds full. Then straighten the glass and pour into the centre, so the last third builds foam. Stop when the head is about two fingers tall.

Pour too gently into a tilted glass all the way and you get almost no head. Pour hard into an upright glass from the start and you get a glass of foam that takes minutes to settle. For bottle conditioned beers, leave the yeast in the bottle unless the style calls for it. Our guide on how to pour beer covers the details for different styles.

Why some beers will not hold a head

Some beers simply make less foam. Very strong beers often foam less, because high alcohol works against foam. Light, highly adjunct lagers often have a thinner head than an all malt beer.

Beyond the recipe, the biggest enemy of foam is fat. Lip balm, food oils and detergent residue on the glass all break it down. Eating fried snacks with your beer can flatten the head sip by sip. That is not a fault in the beer, just chemistry.

Ask for the foam next time

Next time you order a beer, ask for a proper head and watch how long it lasts. At home, pour one beer with two fingers of foam and another with none, then smell and taste both. The foamed glass will smell stronger and taste rounder. That small test changes how most people order beer.

Common questions

How much head should a beer have?

For most beers about two fingers, or 2 to 3 cm. Wheat beers and Belgian ales often carry more.

Is foam on a beer short measure?

Not necessarily. Foam is part of the beer and carries much of its aroma. Many glasses have a fill line so the full measure sits below the head.

Why does my beer head disappear quickly?

Usually because of grease or detergent on the glass. Warm beer and some recipes also hold foam less well.

What is beer lacing?

Lacing is the ring of foam left on the inside of the glass after each sip. It is a sign of a clean glass and good foam.