Too much head. Not enough head. Foam that hangs around, or a head that disappears straight away. Whether you call it foam, froth, or head, you’ve talked about it before, and likely had an opinion about it at some point.

But what is beer foam, and do we want it in our glass?

Why is there foam on a glass of beer?

During the fermentation stage of the brewing process, yeast creates carbon dioxide, which is the main gas you’ll find inside those bubbles. But you won’t find the carbon dioxide in soda water or soft drink forming a head on top of those drinks… so what’s different about beer?

The main players holding together the foam on your beer are proteins from the malted grains (though hop residue and yeast play into it as well). They latch onto the carbon dioxide and hitch a ride to the surface of the beer, where they hang out for as long as they can before the bubbles burst. Head retention - that is, how long the foam lasts on top of your beer glass - is something brewers pay plenty of attention to when they’re trying to perfect a beer recipe.

The ingredients aren’t the only factor though - if you want an admirable head on your beer, you want a clean glass and a good, vigorous pour.

And why do you want a head on your beer?

A healthy head maximises the aroma of your beer

Our sense of smell and sense of taste work together, and so aroma is a huge part of the beer drinking experience. Particularly when you have hoppy beers like pale ales and IPAs, you’re selling yourself short if you’re not inhaling those wonderful aromas.

When your beer has a frothy head, the steady popping of the bubbles as you drink releases the aromatic particles into the air, while also prolonging your enjoyment of that fresh beer smell. Basically, it stops all of the aroma from escaping at once.

A healthy head avoids bloating

When you pour a beer into a glass, you see all the carbonation come out of suspension and form all this voluminous froth. But when you drink straight from the can or bottle, or when you pour so gently that you don’t create a head in your glass, the carbon dioxide doesn’t get disturbed until you send your beer down your throat. That agitation in your stomach is what can cause the bloated feeling we all hate.

In other words, if the head doesn’t form in your glass, it’ll form in your stomach. You don’t want that.

A healthy head helps you drink with your eyes

They say you eat with your eyes first… well, you also drink with your eyes first! (Please don’t literally drink with your eyes. It’ll hurt.)

While the head on a beer doesn’t guarantee anything about flavour, a nice layer of foam sends hints to your brain that this will is a well-made, well-poured glass of beer. Whether it’s the white froth on a refreshing lager or the dark foam on a chocolatey stout, there’s something satisfying about seeing that majestic crown on your beer.

In short, foam is your friend

There are other benefits as well - a glass of beer with a head is harder to spill when you carry it; the foam can add to the mouthfeel of a beer; and of course, foamy beers give you and your friends white moustaches to laugh at.

But whether for its scientific complexity or its delightful simplicity, its sensory amplification or its aesthetic beauty… you’ve gotta love a good head on your beer.