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I have an existing keg of beer that I would like to switch to beer gas. Is this feasible? Are there any problems with doing this?

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How is the existing keg pressurized - CO2, air from a hand pump...? –  mdma Jan 26 at 19:14
    
Existing keg is pressurized with C02 –  Schleis Jan 27 at 14:31

2 Answers 2

Preparation:

  • If you plan to serve the beer through a stout or creamer faucet then it's a good idea to reduce the carbonation in the beer to about 30% of what it was. This can be done by also bleeding off most of the CO2 in the headspace, possibly several times. For example, if the keg is currently 1/3 full of beer, then bleeding the headspace and leaving will reduce the overall carbonation in the beer to 1/3. If the keg is 2/3 full, then you'll need to bleed it 2-3 times, waiting a couple of days for the pressure to increase each time. You could skip this, but you'll end up with a lot of foam in the glass.

Adding beer gas already mixed in the cylinder:

  • bleed the gas from the keg until it's almost empty then fill the headspace to the desired pressure with the beer gas.

Adding pure nitrogen, rather than ready mixed:

  • Reduce the pressure in the headspace. Bleed the headspace until the pressure is about a quarter of your ideal serving pressure. Beer gas is often served at 30 psi with a stout faucet, so 7 psi for the CO2 pressure.
  • pressurize to your target pressure (say, 30psi) with nitrogen.
  • The keg is now full with a mix of 25% carbon dioxide and 75% nitrogen.
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When you say "switch to beer gas" I assume you mean switching from regular air from a hand pump to CO2 on a draft system? If so, there aren't any problems with doing this. However, it has already been exposed to air. So there isn't any benefit in doing so- it will still only keep a few days.

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Beer gas is the name for a 75/25 mix of nitrogen and carbon dioxide. It's often used for stouts. –  Tobias Patton Jan 27 at 17:24

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