Transform & Preserve

Carbonation

Dissolving CO2 into a liquid to give drinks fizz, whether forced or naturally from fermentation.

Carbonation infuses carbon dioxide into a beverage so it releases bubbles and a sharp, tingling mouthfeel when served. Forced carbonation pushes CO2 into chilled liquid under pressure, while natural carbonation traps gas produced by fermentation in a sealed vessel. Cold temperature and pressure increase how much gas the liquid can hold.

Carbonation is the dissolution of carbon dioxide (CO2) into a liquid under pressure, where it forms carbonic acid and produces the visible bubbles, bright mouthfeel, and faint tang we associate with sparkling drinks. It governs everything from the cream on a freshly poured Guinness to the snap of a properly conditioned bottle of saison, and it is the single most important variable a brewer, cider maker, or home soda maker can control. The principle at work is Henry's Law: CO2 dissolves in proportion to the pressure above the liquid, and the colder the liquid, the more gas it will hold at any given pressure. Mastering those two variables — temperature and pressure — is essentially the whole craft.

The technique spans natural and artificial methods. Natural carbonation relies on yeast producing CO2 inside a sealed vessel (bottle conditioning, méthode champenoise, spunding), while forced carbonation pushes gas from a tank into chilled liquid through a regulator. Modernist chefs have extended the idea well beyond drinks, using injected CO2 to aerate purées, lighten batters, and create sparkling fruit purées. Whether you are dialing in 2.5 volumes for a pale ale or 5.5 volumes for Champagne, the toolkit is the same: a pressure source, a sealed vessel, a thermometer, and a carbonation chart to translate your goal into PSI.

In practice, the difference between a flabby pint and a cracking one almost always comes down to temperature and headspace. A keg at 1–3°C (34–38°F) absorbs CO2 several times faster than one at 15°C, and will hold noticeably more gas at the same pressure. Get those two numbers right, give the gas time to equilibrate, and carbonation becomes one of the most forgiving and rewarding techniques in the kitchen.

Difficulty: Medium

Types & varieties

Forced — set-and-forget

Keg connected to a CO2 regulator at a target PSI; gas diffuses into the liquid over 1–7 days. The most repeatable and lowest-effort method, standard for home draft and modern soda.

Forced — shake method

Keg rocked or shaken under 30–40 PSI for 30–60 seconds to accelerate absorption. Slightly less precise but ideal for same-day service or small batches.

Bottle conditioning

Sealed glass bottles trap CO2 from residual yeast consuming a measured priming sugar (typically 3–5 g/L corn sugar for ales). The standard for bottle-conditioned beer, cider, and many natural sodas.

Spunding

Fermentation vessel sealed with a valve that closes at a target PSI, trapping CO2 from active fermentation. Used by German brewers for krausening and Modern Pils.

Soda siphon / iSi whip

One-litre dispenser charged with 8 g CO2 cartridges; quick table-side carbonation for fruit purées, shrubs, and sparkling cocktails.

Countertop soda maker

SodaStream-style machines carbonate single bottles in seconds using refillable cylinders. Best for sparkling water and lightly flavoured drinks.

Inline / commercial carbonation

CO2 injected into chilled, deaerated water at high pressure in a carbonator; the industrial standard for mass-produced soda and sparkling water.

Méthode champenoise

Secondary fermentation in the bottle itself; produces the smallest, finest bubbles and the most refined texture thanks to extended lees contact.

Charmat / tank method

Secondary fermentation in a pressurized tank before bottling; common for Prosecco and large-production sparkling wines. Fruitier profile with larger bubbles.

How to do it

1
Calculate target carbonation
Decide how many volumes of CO2 your drink should hold and look up the corresponding pressure for your keg's serving temperature on a carbonation chart. Most ales at 3°C need roughly 10–12 PSI to reach 2.5 vol; Prosecco-style targets need roughly 18–22 PSI; a true Champagne level needs around 30–35 PSI.
2
Chill the liquid thoroughly
Refrigerate the keg and the liquid to 1–3°C (34–38°F) for at least 12 hours. CO2 solubility is several times higher near freezing, so carbonation is faster, more complete, and more predictable.
3
Connect CO2 and purge the headspace
Attach the CO2 tank, open the valve, and set the regulator to your target PSI. With the lid's PRV open, pressurize the keg to 10 PSI, vent, and repeat 2–3 times to flush oxygen out of the headspace — oxygen is the enemy of fresh flavour.
4
Set working pressure and wait
Leave the regulator at the target PSI, close the PRV, and store the keg at serving temperature. At 30–35 PSI, equilibrium is reached in 3–5 days; at 10–12 PSI, plan on 5–7 days. The liquid is ready when a sample pulled from the sample tap tastes correctly fizzy.
5
Or use the shake method for fast service
Set the regulator to 30–40 PSI, lay the keg on its side or rock it vigorously for 30–60 seconds, then stand it upright and let it rest 5–10 minutes. CO2 goes into solution rapidly; useful when you need a keg ready the same day.
6
Verify and adjust
Pour a small sample. If under-carbonated, raise PSI slightly and wait another 12–24 hours. If over-carbonated, briefly pull the PRV to bleed headspace, agitate gently to release excess gas, and re-check.
7
Bottle conditioning (natural method)
Add a measured priming sugar — typically 3–5 g/L of corn sugar for ales, calculated for temperature and residual gravity — to slightly under-attenuated beverage. Bottle into sanitized heavy glass or thick PET, seal with crown caps or swing-tops, and store at 18–22°C for 1–3 weeks before refrigerating.
8
Maintain during service
Keep the keg at serving temperature with the gas on; pull pints as needed. For long storage, leave gas connected at 5–8 PSI to maintain a positive pressure seal against oxygen ingress.

The physics in plain language

Two knobs control carbonation: temperature and pressure. A carbonation chart cross-references both, telling you the PSI needed at your keg's serving temperature to hit a target number of volumes of CO2. Because cold liquid holds more gas, a keg carbonated at 3°C will be noticeably fizzier than the same keg carbonated at 10°C at the same PSI. The single most common mistake is to set a regulator by feel and then complain the beer is flat — always cross-check with a chart.

Volumes of CO2 (vol) is the number of litres of CO2 dissolved in one litre of liquid at 0°C and 1 atm.
1 PSI ≈ 0.5 volumes at 38°F is a useful starting point, not a law — temperature swings shift it significantly.
CO2 weighs more than air, so headspace gas protects against oxygen ingress and oxidation during storage.

Beyond drinks: culinary applications

Modernist chefs use carbonation to change texture as much as flavour. Injected CO2 lightens purées and gazpachos without the volume loss of whipping, and adds a fleeting sparkle to fruit purées used as palate cleansers. Carbonated batters — tempura, fritters, even pancake batter — fry up with a finer, more open crumb because the bubbles expand on contact with hot oil. Wylie Dufresne, Heston Blumenthal, and Johnny Iuzzini have all used forced CO2 in the kitchen well outside the beverage world.

Carbonate fruit purées and juices for sparkling amuse-bouches and palate cleansers.
Use carbonated water in batters for tempura and fritters for a lighter crust.
Inject CO2 into gazpachos and vegetable purées to lighten texture without aerating with a whisk.

Safety essentials

Pressure and glass deserve respect. Bottle-conditioning bombs are rare but real, almost always caused by over-priming or warm storage; under-attenuated, warm bottles can build 100+ PSI and shatter. For force carbonation at home, never cap glass — use PET soda bottles with carbonation caps, and squeeze the bottle to gauge both carbonation and excess pressure. Always bleed a keg before disconnecting, and never carbonate warm liquid in a sealed vessel expecting it to hold.

Use PET, not glass, for force carbonation with carbonation caps.
Never store priming-sugar bottles above 24°C for the first week of conditioning.
Always bleed keg headspace before disconnecting the gas line.

Common uses

Carbonating water, sodas, and shrubs for service.Carbonating finished beer or cider in a keg to a precise volume of CO2.Bottle conditioning ales, lagers, lambics, and ciders.Making sparkling cocktails (carbonated Negroni, Americano, Margarita) in siphons or with carbonation caps.Producing hard seltzer and kombucha at controlled carbonation levels.Adding effervescence to batters (tempura, fritters) for lighter, aerated crusts.Carbonating fruit purées or juices for a sparkling palate cleanser or amuse-bouche.Injecting CO2 into purées and gazpachos to lighten texture without whipping.

Tips & pitfalls

Always start cold: a keg at 1–3°C absorbs CO2 several times faster than one at 15°C and holds more gas at the same pressure.
Use a carbonation chart rather than guessing PSI — target the style's volumes of CO2 and back-calculate pressure from your actual serving temperature.
For bottle conditioning, use a priming-sugar calculator that accounts for residual fermentables and beer temperature; under- or over-priming causes flatness or bottle bombs.
Sanitize everything that touches the post-carbonation liquid; CO2 alone does not control off-flavour bacteria the way hops and alcohol do in beer.
Use PET soda bottles rather than glass for force carbonation with a carbonation cap, and squeeze the bottle to gauge carbonation and release excess pressure.
Let a freshly shaken keg rest 5–10 minutes before pulling the first pint so the CO2 equilibrates and the pour isn't all foam.
When switching kegs, bleed pressure down before adding the next batch — residual headspace gas will over-carbonate the new pour.
Filter or settle the liquid before carbonating; particulate matter acts as nucleation points and produces foamy, uncontrolled fizz.

Good to know

Principle: Henry's Law: CO2 dissolves in proportion to the partial pressure of CO2 above the liquid; solubility falls as temperature rises.
Temperature: Aim for 1–3°C (34–38°F) for force carbonation; warmer liquid takes far longer to absorb CO2 and holds less of it.
Volumes of CO2 by style: Ales 2.0–2.8 vol; lagers 2.4–2.8 vol; wheat beers 3.0–4.5 vol; Prosecco and most sparkling wines 3.0–4.0 vol; Champagne 5.0–6.0 vol; commercial soda water 3.4–4.0 vol.
Pressure rule of thumb: Roughly 1 PSI ≈ 0.5 volumes of CO2 at 38°F in a balanced keg, but always use a carbonation chart for accuracy.
Equipment: CO2 tank, dual-gauge regulator, Cornelius or commercial keg with PRV, gas line, tap; for bottles, carbonation caps on PET or priming sugar in glass.
Gases: Pure CO2 for most drinks; a 25% N2 / 75% CO2 blend ('beer gas') gives the creamy, low-carbonation texture of stout on draught.
Timing: Set-and-forget at 30 PSI reaches equilibrium in 3–5 days; the shake method produces usable carbonation in minutes.
History: Joseph Priestley published a method for impregnating water with CO2 in 1772; Thomas Henry opened the first artificial soda water plant in Manchester in the 1780s.