There’s something magical about nitrogenated beer. To the uninitiated, the cascading bubbles and thick, froth-like head may not even seem beer-like. It’s more evocative of a decadent dessert or blended coffee drink than a crisp beer.
Not long ago, beer served with nitrogen gas was either considered exotic or a novelty. As the craft beer market surged, serving nitrogenated beer was something of a distinction, in that it took specialized equipment as well as a certain amount of extra care and consideration. Today, you average sports bar may have upwards of three dozen draught lines and at least one dedicated solely to pouring nitro beer.
But what is nitro beer?
Carbonation in beer occurs naturally as a byproduct of fermentation—yeast create CO2 as they consume sugars and excrete alcohol. For many centuries, this natural carbonation was the only source of bubbles in beer. Today, the vast majority of beer is force carbonated, meaning a specific amount of carbonation is forced into the liquid under pressure, with the exception of bottle or cask-conditioned ales. Nitrogen, however, does not just appear in beer—someone has to put it there.
Nitrogenated beer’s roots lie in Dublin. Jeff Alworth's “The Man Who Invented Guinness” goes into great detail about this history, but basically the gist is this: Draught beer in Ireland was a finicky and inefficient beast and one man at the Guinness brewery set out to refine it. Nitrogen, being stable and inert, seemed to be a perfect dispensing gas. Once the technical hurdles were overcome, it was a massive success. As Alworth notes, nitrogenation “revolutionized Guinness and Irish stout.” Guinness has become synonymous worldwide with nitrogen and the fine, tiny bubbles it creates, which give the beer its creamy texture.
While nitro beer originated as a draught-only product, in the late 1980s Guinness launched nitrogenated canned beer for the first time. “Draught cans” of the black stuff contain a small plastic ball containing residual nitrogen gas and beer under pressure—known colloquially and throughout the industry as a “widget.” When the can is opened, the pressure drops and the beer and gas inside the widget are forced through a small hole via the pressure differential, which releases the nitrogen, creating tiny bubbles and the signature frothy head. This process was later re-created in the bottle via the oddly shaped “Rocket Widget.”
In America, packaged—an in bottled or canned, rather than kegged—nitro beer began with Left Hand Brewing Co. in Longmont, CO. Left Hand’s iconic Milk Stout is a 6% ABV sweet stout that has a lovely balance of dark chocolate and coffee flavors along with its signature lactose-sugar derived sweet creaminess. In 2011, Left Hand became the first American craft brewer to successfully bottle a nitrogenated beer and the black Milk Stout Nitro bottle quickly became iconic in itself. Left Hand has since followed with a number of other nitrogenated bottled bres, such as their decadent Wake Up Dead imperial stout and classic ESB-like Sawtooth Ale.
After Left Hand came le déluge. Since 2011, a flood of package nitro beer options have come and gone, from Sam Adams’ Nitro Project cans to Oskar Blues’ Old Chub Nitro and Breckenridge Brewery’s rotating nitro pounder cans. All of the aforementioned brands contained a widget and operate according to the same principle as Guinness’ revolutionary cans. Left Hand recently moved into the canned category as well and employ the same American-made, top-hat-like widget used by Sam Adams.
So, why no widget in the Left Hand bottles? It’s good question with no immediate answer. Left Hand has been notoriously secretive about its proprietary widget-less bottled nitro beers. Whatever they’re doing, though, it undeniably works. Both bottles and cans recreate the experience of a draught nitro beer beautifully.
Firestone Walker’s new Nitro Merlin is a different beast than Left Hand’s nitro beers. While still recognizably a sweet stout, Merlin is soft and chocolatey where Milk Stout is roasty and coffee-like. With aromas of café au lait and a touch of anise, it’s a complex beer for sure, though one that would still appeal to your basic Guinness drinker, especially given its lower ABV.
The canned version of Nitro Merlin bears no widget. Instead, the label instructs drinkers to “master the surge pour” by inverting the can several times and then “pouring hard” by turning the can 180° and pouring directly into the bottom of the glass. Similar instruction appear on Left Hand’s nitro packaging. As noted on Firestone Walker’s website, inverting the can “agitates the nitrogen” living both in solution in the beer. The page goes on to explain the widgetless magic that makes Nitro Merlin possible: Instead of forcing gas into the beer, a drop of liquid nitrogen is added to the beer during packaging, "which immediately flashes off into nitrogen gas. As the can is filled and sealed, a portion of the gas fills the head space while the remainder remains suspended in solution—only to be released when the can is cracked by the beer drinker."
The result is fantastic. As nitrogen bubbles come out of solution and rise to the top of the glass, the beer goes momentarily pale before it resolves into a beautiful inky black with a frothy off-white head resembling latte foam.
Nitro beer isn’t for everybody. While creating that smooth, full mouthfeel and frothy head, nitrogenation also diminishes the carbonic bite that many people associate with the experience of drinking beer. Aromas are also dulled. This is especially true of hop aromas, which has made the emergence of nitro IPAs in the past decade somewhat polarizing. Still, there’s no denying that when well-executed, nitrogenation makes for a singular drinking experience.