Kegging & Carbonation
The other half of packaging — force carbonation, serving pressure, low-oxygen closed transfer, and carbonation targets by style. Pairs with the bottling section of the brew-day walkthrough.
On this page
The brew-day walkthrough covers bottling. Kegging is the other route: faster than bottle conditioning, reusable, and — done with a CO₂ purge — much kinder on the beer’s freshness because you can keep oxygen away from it throughout. This guide covers carbonation theory, force carbonation, low-oxygen transfer, and serving.
Carbonation, measured
Carbonation is dissolved CO₂, measured in volumes of CO₂ (litres of gas dissolved per litre of beer). Cold beer holds more CO₂ than warm, so carbonation is always a relationship between pressure and temperature — the same PSI gives different carbonation at different temperatures (use a carbonation chart or calculator).
Targets by style
| Style group | Volumes CO₂ | Serving PSI (typical) |
|---|---|---|
| British / cask ales, some stouts | 1.5–2.2 | 5–10 |
| Standard ales — IPA, Pale, Amber, Wheat | 2.4–2.6 | 12–14 |
| Lager / Pilsner | 2.2–2.5 | 10–14 |
| Belgian, sours, high-gravity | 2.6–3.0+ | 15–18 |
Force carbonation
Slow method (recommended, 2–3 weeks). Set the regulator to your serving pressure for the style and temperature, connect gas, and wait. Gentle on seals, hard to overshoot, and it lands at exactly serving pressure — no rebalancing.
Fast method (5–7 days). Hold at a higher pressure (~30–35 PSI), optionally rocking the keg to speed CO₂ uptake. Quicker, but you must drop back to serving pressure (and vent the excess) before pouring or it foams.
Either way, chill the keg first — CO₂ dissolves far better cold, and carbonation pressure is set for the serving temperature.
Keep oxygen out
Oxygen is the enemy of finished beer (stale, cardboard flavours). Kegging’s big advantage is that you can exclude it:
- Purge the keg with CO₂ before filling — fill the empty (sanitised) keg with CO₂, pressurise to ~2 PSI and vent, three times, to displace the air.
- Closed / diptube transfer — rack from the fermenter into the keg through the
liquid-out post and diptube so the beer fills from the bottom up under CO₂,
not splashing through air:
- Pre-purge the keg, then release all pressure before connecting.
- Prime the transfer line so beer, not air, is first into the keg.
- Crack the pressure-relief valve so displaced CO₂ can escape as beer rises.
- Keg dry-hopping — add hops to the keg before the CO₂ purge, so the purge also removes oxygen from around the hops.
Safety: never seal a keg on beer that hasn’t fully finished fermenting. Residual fermentation in a sealed keg can build dangerous pressure, especially if a diptube or relief valve clogs with hop debris. Confirm terminal gravity first.
Filling and a weight trick
Fill to about an inch from the top (leave headspace for CO₂). The tidy way to hit a target volume is by weight: tare your empty keg, then fill to the target total. For a Kegland corny keg (empty tare ~4.25 kg), filling to a total of ~23.25 kg gives roughly 19 L of beer.
Bottle conditioning vs kegging
Bottling carbonates by feeding the yeast a measured priming sugar dose in the sealed bottle (the walkthrough uses 2 carbonation drops per 750 mL → ~2.4–2.6 volumes). Kegging carbonates with gas under pressure. Same destination, different road — kegging just gives you a dial instead of a one-shot sugar calculation.
Troubleshooting
- Won’t hold pressure — leak. Soapy water on every post and connection; listen for hiss; replace worn O-rings.
- Flat after force carbonating — keg leaked or lost pressure; re-pressurise and wait another 5–7 days.
- Too foamy / over-carbonated — pressure too high, or warm. Reduce regulator by 2–3 PSI, vent the keg, wait 48 h; check serving line length/temperature.
- Stale / cardboard — oxygen got in during transfer. Tighten the purge and use closed diptube transfer next time.