What makes for the ultimate beer drinking experience? Some like theirs in a frosty glass, others with a wedge of lime. But when it comes to froth - or the head as it's commonly known - what's the best amount and how can it be achieved?
Too much froth and you're left with a smear of bubbles across your face and hanging from your nose as you desperately try to get at the beer beneath. But too little will cause problems in your stomach.
You see, if there's no foam the CO2 stays dissolved in the beer. If you then eat something, the foam erupts in your stomach rather than the glass, causing beer bloat. That's why tipping a glass to avoid a frothy head is a rookie error.
Hoping to solve this issue, a company in Japan has designed a beer can with two pulls, which control the level of foam produced by opening the can, resulting in the perfect amount of froth.
This is just the most recent development in beer technology. Humanity has been chasing the perfect pint since beer's inception, which evidence suggests was roughly 13,000 years ago near Haifa, Israel - the oldest known record of human-made alcohol.
Under pressure
Beer consumption has evolved through the ages.
Those first producers and consumers of beer in Israel were the Natufian people, a group of hunter-gatherers in the eastern Mediterranean. Their beer would have been unfiltered, which made it look like thin porridge.
This led to the invention of beer straws around the fifth to the fourth millennium in Iran and Iraq, which featured a filter on the tip that held back the beer solids. These straws were similar in design to a modern bombilla (a yerba mate tea straw used for at least four centuries in South America).
The next significant leap in brewing was not the glass bottle, but another airtight closure: the barrel.
Advances in cooperage (the making of wooden casks and barrells) during the Middle Ages meant that the CO2 produced by yeast during fermentation remained in the solution within the container, rather than dissipating and giving it the porridge-like consistency of previous beers. This meant beer could be held and dispensed under pressure for the first time. This inexorably altered the appearance and flavour of beer, as it became effervescent and foamy when served fresh.
Foam was a vital component of proper beer because it showed its freshness.
A good head
The foamy head was at one time called a "collar" - a term that first appeared in print in John Steinbeck's 1945 novel Cannery Row. There seems to be no origin story attached to the monicker. And sadly, there seems less need to apply a name to beer foam since society has strayed from proper beer pouring techniques.
Traditionally, beer was allowed to foam up so much as it was being poured that a "foam scraper" (also known as a "foam flipper" or "head cutter") was needed to shave the excess off the glass rim. A large head was achieved by pouring the beer in an upright glass and encouraging excessive foaming. This technique dissipates the trapped CO2 and brings positive flavour elements to the forefront.
These days you'll notice that glasses are tipped while beer is poured. This is done to minimise foam but leads to a less pleasurable, gaseous experience instead of a creamy, toasty sip.
Next time you order a pint you should ask your bartender to pour the amber stuff into an upright glass. This is all to say, don't fear the foam, it's integral to your enjoyment.
Anistatia Renard Miller, PhD in History, University of Bristol