Barley Mowat 

Nitro That Fridge

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Now that everyone has read my great how-to guide for setting up a 50L beer fridge, it’s time to take it to the next level: moving to a nitrogen tap. This step will involve throwing out about half the gear you bought in my previous guide, so I guess that teaches you for not reading through until the end before starting, eh?

Say “Nitrogen-tap” and 9/10 people will respond with “isn’t that for Guinness?” While it is true that Guinness is using an N2 tap to up-market a rather boring, insipid stout, what most people don’t realize is that any beer you care to quaff can be moved to N2 yielding you that rich creamy goodness.



Like this, only with good beer.

Before we get going, though, you need to decide if a N2 tap is even your thing. Like all things beer, there are both pros and cons to making this leap. Here’s the Coles Notes version:

Pros:

  • Pours a rich, creamy head that lingers
  • Has that cool cascade effect
  • Gives you serious beer geek cred

Cons:

  • Nitrogen costs more than CO2, and is sometimes only available in huge containers
  • Requires special tap
  • Requires long prep steps to get normal kegs to work
  • Pours much slower than CO2
  • Makes regular CO2 pours harder without using separate CO2 tank

So, basically it boils down to how patient you are. If you need to get drunk as fast as possible, this might not be the trick for you (I recommend chugging vodka instead).



I suspect the GIS results for “chugging vodka” are largely at odds with the reality of the matter.

So now we’re committed. What do you need to do?

  1. Trade in your CO2 tank for a blended 70-75% N2, 25-30% C02 tank. This mixture is commercially known as “Beer Gas.” I shit you not.
  2. Purchase a “euro-style” tap like this one. This doesn’t just look all continental, but also contains the magical diffuser plate that forces the nitrogen into the beer as it pours.



Diffuser plate, o-ring, and tap nozzle. Sartori provided for scale. And jealousy.

So that’s it right? Hook that crap up and voila, you have nitro’d beer? Anything but. You see, freshly-brewed beer is actually rather flat (ever had a cask ale?). While the yeast does provide some amount of carbonation, it is nowhere near the soda-pop levels we’ve become used to in our ales. For this reason, the last step before beer is bottled or kegged is called “forced carbonation.”

“Forced carbonation” is just that, artificially forcing lots and lots of CO2 into beer to give it that satisfying fizz. This is problematic for us because in order to get the N2 into the beer, we need to first get the CO2 out. There are lots of ways to do this, but the method I prefer is to occasionally bleed off the excess gas because I’m lazy and this method involves drinking beer.

The CO2 in the beer is at a pressure somewhat higher than atmosphere (typically 5-14psi, depending on your brewery and beer style). If you tap the keg with your gas valve off, then vent it, you’ll remove that excess CO2, but only from the head space (the non-beer part of the keg).

So now you have a keg that is mostly fluid at +5-14psi and a little bit of CO2 at +0psi. Over time the liquid beer will equalize with the gaseous headspace, returning the headspace to +5-14psi and lowering the pressure in the beer a wee bit. The problem is that the head space in a new keg is so tiny that you’ll need to repeat this step dozens or hundreds of times to get the liquid part down to zero-ish. Here’s how to speed things up:

  1. Take out your diffuser plate from the tap (see instructions that came with it).
  2. Pour pints/pitchers with your gas valve off until no more comes out. At this point the head space has 0psi
  3. Drink the beers you just poured. I cannot stress the importance of this step enough. This gives the beer in the keg time to equalize with the headspace, but more importantly lets you drink beer.
  4. Repeat. If the keg stops equalizing we’re done. If you stop standing, go to bed and pick it up first thing in the morning. Screw jobs, man, this is important!

If you’re impatient or very strong, feel free to give the keg the occasional shake to encourage the beer to let go of the CO2. Once we’ve got the beer down to 0-5psi of CO2, open the value to your N2 tank and let it equalize again. It will take a while for your keg to absorb the N2, but again shaking it from time to time will help speed things up.

Now the question is what pressure do you want your N2 at? Most people recommend 30-40psi to give you a solid pour, but also to keep the right level of CO2 in the beer (setting it to, say, 8psi gives you much less CO2 in the beer because Beer Gas is only ~30% CO2, remember). I’ve found the optimal pressure changes from beer to beer, so fiddle around and find the level you like.

Now put that diffuser plate back in and you’re off to the races.



Pictured: The Races.

Written by chuck

December 28th, 2010 at 1:28 pm

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  1. […] right? Well, not really. Guiness of course uses nitrogen to make those bubbles, which is different (more detail on why). Molson is just using regular old CO2 to force carbonate their regular “lager” […]

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