Serious Eats: Drinks
The Flux Capacitor: A Tool for Better Beer on Tap
With the openings of Tørst in Brooklyn and the States' first Mikkeller Bar in San Francisco, there are two words on the lips of anyone who has ever managed a beer bar's draft system: Flux Capacitor.
No, this isn't some semi-ironic revival in appreciation for Back to the Future (that movie's always been cool). The Flux Capacitor is the name that Gabe Gordon has applied to the system of secondary gas regulators he's installed at Torst, Mikkeller, and the two locations of his restaurant, Beachwood BBQ in Southern California. Secondary regulators? I can hear you clicking you back buttons from here. Let me explain why this is important.
Aside from being super cool looking, the Flux Capacitor ensures that a bar is easily able to present beer at its absolute best. How? The key word is balance.
Every draft beer you've ever drunk has arrived to that establishment containing a specific level of carbonation. Brewers refer to this in terms of gigawatts...er, I mean "volumes of carbon dioxide." This is the volume of dissolved gas held within that same volume of beer. A liter of beer containing 2 volumes of carbon dioxide, for example, contains two liters of dissolved carbon dioxide, which is released as those bubbles in your beer.
The responsibility to maintain the level of carbonation that keg rolls in with rests on the shoulders of whoever is managing the draft system. When the manager taps a keg, he is applying a set amount of gas pressure (usually from pre-filled canisters of carbon dioxide and/or nitrogen) to the surface of the liquid in the keg to push the beer to the faucet and ultimately to your thirsty taste buds. But it isn't that easy. The manager must achieve balance by applying just the right amount of gas pressure, or your beer is going to be screwed up.
There are a lot of factors that dictate exactly what that pressure is for every keg, including the distance to the faucets, the diameter of the beer tubing, temperature, and well, lots more things. Put simply, if the tapper applies too little pressure, the keg will slowly lose carbonation. If there's too much carbon dioxide pressure applied, the gas is absorbed into the beer, resulting in an overcarbonated keg. Either way, the result isn't likely going to be what the brewer intended, and it will cause the beer to be too foamy at the faucet.
Too-foamy beer means longer pour times or shorter pours for the customer, and inefficient bartending and wasted beer for the bar. Foamy pours and dumped pints cost money and waste time, and the over- or under-carbonated beer won't taste like it should. So you can see why applied pressure control is important.
This is where the Flux Capacitor comes in. A set of gauges, called secondary regulators, allow anyone with a flathead screwdriver to quickly and easily adjust the individual pressures applied to every keg. Now that capability is absolutely not unique to these DeLoreans-of-draft-systems. In fact, just about any bar that takes its beer seriously has the ability to adjust individual keg pressures.
But the Flux Capacitor is cool for three reasons. First, it allows the manager to adjust not only the amount of pressure applied to each keg, but also the composition of the gas that is being put out. In the most simple draft systems, 100% carbon dioxide is used to push beer to the faucet, but many bars have more complex systems and a blend of nitrogen and carbon dioxide is needed. This is so that the bar can apply really high pressures to the kegs (say, to push the beer long distances or at warmer temperatures, in which the beer's carbonation breaks out more easily) without overcarbonating them—nitrogen is not as easily absorbed by the beer as carbon dioxide is. The Flux Capacitor allows for individual control over this blend, which gives bars the freedom to serve draft beer at the warmer, more desirable temperatures (say 50-55 degrees) that brewers view as ideal.
Second, the Capacitor makes draft maintenance easy and elegant—no more dangerous teetering on kegs to reach behind shelving, no more slipping on pools of line cleaner or accidental screwdriver stabbings. This is easier, faster, and quicker maintenance. This ensures that it will actually, you know, happen. And right away. On-the-fly adjustments aren't possible in ultra-busy, lean-staffed bars—especially if the bartender has to leave the floor to make them.
Finally, the visually striking Flux Capacitor increases awareness. A wall of gadgetry in a bar will get people asking questions. This will inevitably lead to a deeper public understanding of how beer works, and that can't be a bad thing.
Is the flux capacitor completely revolutionary? Maybe not. But it's extremely helpful, and it looks undeniably cool.
Foamy kegs? Where we're going, we don't need foamy kegs.
About the author: Mike Reis is a Certified Cicerone and Co-Director of Beer at the Monk's Kettle and Abbot's Cellar restaurants in San Francisco. Follow him on Twitter @beerspeaks or find him behind a pint near you.
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