How to Force Carbonate a Keg

Method 1

Set and forget -- the one to use

The reliable method, and the one to default to.

1. Chill the keg to serving temperature and let it get there fully. Around 38°F for most beers. This step is not optional -- CO2 solubility depends on temperature and carbonating a warm keg means carbonating against the physics.
2. Set the regulator to your target serving pressure. Roughly 10 to 12 psi for most ales at 38°F; see CO2 regulator settings for styles.
3. Connect the gas and leave it. Two to three days. Taste on day two, and if it is close, leave it one more day.
4. Leave the gas connected permanently at serving pressure for the life of the keg.

Why this is the right default: the equilibrium carbonation at a given pressure and temperature is fixed, so the beer cannot over-carbonate no matter how long you leave it. It is self-correcting. The only cost is patience.

Method 2

The shake method -- fast and easy to overshoot

If you need carbonated beer this evening:

1. Chill the keg thoroughly first. Cold beer absorbs CO2 much faster.
2. Set the regulator to around 30 psi.
3. Lay the keg on its side and rock it back and forth for 60 to 90 seconds. You will hear gas flowing into it as the agitation drives CO2 into solution.
4. Stand it up, drop the regulator to serving pressure, and vent the keg.
5. Wait an hour, then pour a test glass.
6. Repeat in short bursts if it needs more.

The risk is real: agitation drives CO2 in faster than you can judge, and an over-carbonated keg is much more annoying to fix than an under-carbonated one -- you have to vent it repeatedly over days and wait for equilibrium to re-establish. Do short bursts and check, rather than one long shake.

Method 3

The burst method -- a sensible compromise

Between the two: set around 30 psi, leave it connected for 24 hours without shaking, then drop to serving pressure and vent. Taste after a few hours.

This gets you most of the way in a day with far less overshoot risk than shaking, because there is no agitation accelerating absorption unpredictably. It is the method to use when you want it ready tomorrow rather than tonight.

Before you blame carbonation

Three things that look like a carbonation problem

• A leak. A keg that never carbonates despite days at pressure is usually leaking. Pressurize it, close the cylinder valve overnight, and see whether the gauge drops. Check the lid gasket and post O-rings first.
• A short beer line. If the beer is correctly carbonated but pours as foam, the line is too short to drop keg pressure to zero at the faucet. Add line rather than lowering the pressure, which would under-carbonate the beer.
• The keg not actually being cold. A keg put in a cold cabinet a few hours ago is not at 38°F throughout. Carbonating against a warm core gives inconsistent results.