If you’ve ever ordered a pint of Guinness, you probably know it takes longer to arrive than your barmate’s Bud. In fact, Guinness has an official measure of just how much longer it takes—119.53 seconds. That’s the time it takes for the beer to settle in between the first and second pours in the company’s all-but-patented “two-part” pouring method. And with roughly 10 million pints of Guinness Draught sold globally each day, that adds up to almost 38 years combined that people across the world spend waiting on a Guinness pint every 24 hours.
According to Guinness’s website and Irish bartenders everywhere, this two-part pour is designed to produce the perfect ratio of the dark liquid draught (actually a deep ruby color when held up to any light source) and the cream colored, mouse-like head while preserving the thick, velvety mouthfeel of the beer. But how exactly is this accomplished? Guinness instructs:
“First, start with a clean, dry glass [Guinness branded preferably, but any tulip shaped glass will do]. Pour the Guinness Draught into a glass tilted at 45 degrees, until it is three-quarters full. Allow the surge to settle before filling the glass completely to the top. Your perfect pint, complete with its creamy white head, is then ready to drink.”
Seems pretty simple, right? But there’s a lot more going on behind the keg lines than meets the eye, scientifically and psychologically.
We’ll start with the scientific. The origins of this two-part pour are somewhat of a mystery (Guinness would not reply for a request for comment by deadline, though we’ll update if we hear back). But Luke Baily of BuzzFeed UK proffered one theory:
“During the 1950s, Guinness replaced their traditional wooden casks with nitrogen-charged metal casks, but customers were unconvinced. Regular Guinness drinkers needed to be persuaded that the new stout was just as good as the cask-conditioned version.”
In order to convince wary drinkers that the new casks were just as good as the old, he argues, Guinness instructed bartenders to pull about three-quarters of the pint from the cask-conditioned stout, and top it off with the new, nitrogen-infused version, providing it with a more silky and creamy head. Thus, “the two-pour method had briefly been necessary during the decade-long changeover from wooden to metal casks,” but by the end of the 1960s, “this was rendered effectively obsolete by the new dispenser technology.”
It’s the use of nitrogen in Guinness that makes it unique among historical stouts, and what still makes its pouring methodology (somewhat) necessary. Most beers are pressurized in the keg with carbon dioxide exclusively (i.e. carbonated), while Guinness maintains a ratio of 75% nitrogen to 25% carbon dioxide.
This is what is commonly meant when you hear the phrase “on nitro.” A handful of other beers, like Left Hand’s Milk Stout Nitro (which arguably started the nitro beer renaissance in 2011), but also Oskar Blues Old Chub, Vault brewing’s Nitro Coffee Stout and Rye Pale Ale, and even limited offerings by Sam Adams, have all become somewhat widely available in the U.S. in the past seven years. And you may have even heard of certain coffee shops selling iced coffee on nitro. But there’s no denying that Guinness was the first and original.
Nitrogen bubbles are significantly smaller than carbon dioxide, and thus rise at a denser rate than the carbonated bubbles of traditional beers. This has the effect of creating the classic lighter-colored domed head at the top of a Guinness by trapping the liquid beer around the bubbles and preventing the nitrogen from escaping. It also makes the beer itself creamier on the palate, with a somewhat silky or velvety texture when drunk, as it should be, through the foam head.
All nitro beers take longer to settle than carbonated beers because of the difference in density of gaseous bubbles. A single pint of Guinness has 300 million bubbles, according to Forbes. And it takes a while for all those surging molecules to finally find equilibrium – hence, the scientific reason for the two-part pour to prevent a head that is either too thick as to be undrinkable, or too thin, which would eliminate the signature sensation of a Guinness mustache.
The most important, and time consuming process of the Guinness pour is allowing the surge to settle between the first and second pours, and later, allowing for the second pour to settle. But you might also notice something a little, off, about how the pint itself separates. The bubbles appear to be moving downward, defying the laws of physics that we can all see in the carbon dioxide bubbles rising, as in a standard beer. To many, this is what makes the ritual of waiting for a Guinness so enjoyable, watching the perfect separation happen. But does it have to do with the pour technique itself? Sujata Kundu at Forbes has the answer:
“As these [nitrogen] bubbles rapidly rise, they make way for more liquid Guinness which falls towards the bottom of the glass to displace the bubbles and the liquid that have moved upwards. As the flow of bubbles in the central core of the pint is quite fast, the Guinness on the sides of the glass is the only liquid that can counter the direction of flow, and so circulation is created in the glass. As the Guinness on the sides falls to the bottom of the glass, some of these tiny nitrogen bubbles are swept downwards with it, overcome by the larger downward force.”
When pouring nitrogenized beer, the tap lines must also dispense the beer with gases at the same ratio as the gases in the keg (a 3:1 ratio for Guinness, which also requires exactly 38 pounds of pressure exactly). The ideal temperature for Guinness, and most other stouts, is 42 degrees Fahrenheit in order to release the most of the beer’s flavor palate. Unfortunately, most bars keep their beers at 35-38 degrees, compromising the taste of what could otherwise be a perfect Guinness pint. And when the Guinness comes through the tap, it passes through a restrictor disc, a small piece of metal punctuated with holes that breaks the nitrogen out of the stout, allowing the rest of the physics in the glass to take place at all.
When Guinness settles, the nitrogen bubbles appear to move downward. (via GIPHY)
In a (very) pseudo-scientific experiment, I went to my local to see what would happen if I ordered two Guinnesses. The first, I ordered normally. Drank it (in part to steel myself up for what I was about to ask). I got up, approached the widest gap in the bar and stood as far away from any other customers as I could. Then I asked it.
“Could I have another Guinness? But I have a weird request. Could you pour it like a normal beer?”
And then the last thing I expected to happen happened. The bartender said, “Yeah for sure, no problem,” in the kind, “of course” tone of a customer service professional who tries not to let you down in your belief that your question was original or unexpected. In other words, I wasn’t the first to ask for my Guinness unceremoniously.
I drank it. Trying to discern a difference between the first. It may have been slightly more bitter? Or maybe I was expecting it to taste slightly more bitter. Hard to tell. The head was approximately 1-2 millimeters larger than the first and did not have the dome effect over the lip of the pint glass. I suppose as a result I technically got somewhere between zero and half an ounce less beer on the second pour. If I had to guess though, not being a statistician but being a frequent beer drinker, that’s within the margin of error for bar pints, carbonated or nitro. In essence, only to the most discerning palate would it matter whether the two-pour pint was respected, and any talented bartender should be able to produce near identical pints regardless of the pouring process.
I asked my bartender afterwards if any other nitro beers require or suggest a two-part pour and her answer was an unequivocal no—Guinness is the only one. But she did say something that caught me off guard. She said that it’s easier to get the pour amount right in Guinness’s 20oz glass with the two-part method because it’s not a standard 16oz American pint, but rather an Imperial pint, used almost exclusively in Ireland and the UK. In her experience, having the opportunity to let the beer settle and wait to top it off leads to a more consistent outcome because, however close you get to cutting off the tap at the top of a 20oz pint, there is far too much variability in the settling process to create uniformly measured beers. Instead, it’s better to fill the glass roughly three-quarters, wait, and top it off slowly, and accurately, every time, creating a more consistent experience for the consumer. And that, after all, is the goal of any good customer service experience.
So while it may not have to do with flavor or mouthfeel, there may legitimately be something about the two-pour” pint that, in America at least, actually ensures your “perfect pint” is in fact a precise 20oz Imperial pint of Guinness that looks the way it is expected to look, every time.
“It is a ritual. It’s theater. It’s about creating an experience,” Guinness brewmaster Fergal Murray told Esquire in 2007. Which is to say the Guinness pour is part necessity, and part performance, and part marketing, helped along by one of Guinness’s most iconic advertising slogans, which first appeared in 1996: “Good things come to those who wait.”
The “perfect pint,” with its half-inch head of foamy draught, is as much a function of drinkability as it is of self-promotion. Guinness wants us to believe that this is what a pint of Guinness should look like, and the more consistent bartenders are around the world at pulling such ideal pints, the more it will be expected, creating a feedback loop perpetuating the expectation of a perfect pint devised by Guinness itself.
Where does this leave us though in the quest to find the perfect pour? To my mind, the designation of the “perfect pint” or “perfect pour” is almost exclusively an aesthetic one. Nearly all but the stodgiest experts agree that, all things being equal behind the tap, the taste of Guinness doesn’t change based on how it’s poured. And the reason some bars may be known for the “best” pint has more to do with maintaining their tap lines, both in terms of constantly confirming the correct nitrogen to carbon ratio and pressure and cleaning, as well as cleaning the restrictor disc, and ensuring that Guinness is stored and served at the recommended 42 degree temperature.
This isn’t to discount the importance of the look of Guinness in one’s enjoyment of it. After all, a good indication of what goes on behind the scenes is the attention to detail in the final presentation of a pint. If a pint looks off, it might be an indication that something far more affecting of the beer’s flavor might be off in the cellar. Style makes the man, as they say. And there’s no denying the handsomeness of a deep ruby Guinness topped with a mocha cream head separated by a line that approaches godliness in its perfect delineation between light and dark.
Guinness has always known how to capitalize on their product’s unique qualities, marketing it around its individuality. This, arguably, goes back to the days before they marketed it at all, letting news of its quality spread among the Dublin docks by word of mouth. So when, in the latter half of the 20th century, customers started to get testy about having to wait loner for the only nitro beer available, they capitalized on that, too. Good things come to those who wait. Unless you don’t care about aesthetics. In which case just order it and ask your bartender to pour it like a Bud, you heathen.
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