carbonation
Bottle conditioning
Carbonate beer through a secondary fermentation inside the sealed bottle, using residual or freshly-added yeast with priming sugar.
What is actually happening
- Prime and seal. A calculated quantity of fermentable sugar goes in at packaging, with live yeast either carried over or freshly added. The bottle is closed immediately — the seal is what makes the rest work.
- Ferment inside the bottle. The yeast ferments that sugar over two to six weeks. The carbon dioxide cannot escape, so pressure rises until it dissolves into the beer. The remaining yeast also scavenges oxygen, which is why beers meant to keep are packaged this way.
- Sediment, and how to pour. The yeast settles to the bottom. Pour in one movement and stop before it reaches the neck, or rouse it deliberately if the style calls for it. Get the priming sugar wrong and the same closed system becomes a hazard.
A calculated quantity of fermentable sugar is added at packaging. The yeast ferments it in the sealed bottle, and because the CO₂ cannot escape it dissolves into the beer.
The live yeast that remains continues to scavenge oxygen, which measurably slows staling. This is why beers intended to keep — Belgian abbey ales, English strong ales — are traditionally packaged this way.
The cost is a yeast sediment, and a real hazard if the priming calculation is wrong or fermentation had not finished.
Typical conditions
| Duration | 2–6 weeks |
|---|---|
| Scale | Used at both homebrew and commercial scale |
Ranges, not targets. These describe what is usual across the styles and breweries that use this step, and a value outside the range is a decision rather than an error.
What goes wrong here
Risks rather than certainties. This step does not cause these faults; getting it wrong can.
- Overcarbonation — Too much dissolved CO₂, from over-priming, incomplete fermentation before packaging, or contamination.
- Gushing — Beer that erupts on opening, caused either by refermentation in the package or by fungal proteins from mould-affected barley.
- Undercarbonation — Too little dissolved CO₂, leaving the beer flat and dull — carbonation carries aroma as well as providing texture.
Styles where this step is decisive
- Tripel
A strong pale Belgian ale that is simultaneously rich and dry, with pepper, orchard fruit and a sparkling, deceptive drinkability.
- English barley wine
The strongest traditional English ale: dense malt, dried fruit and marmalade, built to be kept for years.
- Weissbier
Bavarian wheat beer defined by its yeast: pronounced banana and clove over a soft, cloudy, highly carbonated body.
- Dubbel
A dark Belgian ale rich in raisin, plum and caramel from dark candi sugar, dry-finishing despite its sweetness of flavour.
- Belgian blond ale
A moderately strong golden Belgian ale, soft and lightly sweet, with gentle yeast fruit and spice and a dry finish.
- Belgian single
The low-strength pale beer brewed for the monastery’s own table, dry and hoppy with full Belgian yeast character.
- Belgian golden strong ale
Pale, very dry and highly carbonated, with intense pepper and fruit and a strength its lightness completely conceals.
- Belgian dark strong ale
The strongest of the Belgian dark ales: raisin, fig and dark caramel over substantial warmth, with a surprisingly dry finish.
- Belgian pale ale
An everyday Belgian ale, toasty and biscuity, with restrained yeast character compared with the stronger Belgian styles.
- Belgian table beer
A very low-strength everyday Belgian beer, historically served with meals including in school canteens.
- Saison
Dry, peppery and highly carbonated, with a bracing finish — the most refreshing thing strong beer does.
- Grisette
A low-strength Walloon farmhouse ale, historically brewed for miners — dry, wheaty and gently peppery.
- Bière de Garde
A malty, rounded French farmhouse ale brewed for keeping — richer and less peppery than its Belgian saison cousin.
- Witbier
A Belgian wheat beer brewed with unmalted wheat, coriander and orange peel — soft, hazy, citrusy and lightly spiced.
- Gueuze
A blend of young and old lambic, refermented in bottle — intensely complex, bone dry and Champagne-like in its carbonation.
- Fruit lambic
Lambic refermented on whole fruit — traditionally sour cherry or raspberry — producing a dry, tart, intensely fruity beer.
- Dunkelweizen
A dark Bavarian wheat beer where banana and clove meet bread crust and light caramel from Munich malt.
- Weizenbock
A strong wheat beer combining Weissbier yeast character with bock malt depth — banana and clove over dark fruit and bread.
- Roggenbier
A German rye beer, spicy and full-bodied, fermented with Weissbier yeast for banana and clove alongside rye’s pepper.
- British strong ale
A broad category of strong English ales, malt-led and fruity, sitting between strong bitter and barley wine.
- Australian sparkling ale
A highly carbonated, bottle-conditioned Australian pale ale, fruity and dry, traditionally poured to rouse its yeast.
- Old ale
A matured English strong ale with dried fruit, treacle and often a trace of oxidative or wild character from age.
Related steps and concepts
- Priming — The calculation it depends on.
- Force carbonation — The alternative.
- Sediment — What it leaves.
Also at the carbonation stage
Force carbonation · Krausening · Nitrogenation · Priming
See the whole process in order on how beer is made.
Last reviewed 2026-08-16.
Evidence
What BeerHQ knows about this, and how. Every statement carries the state of the evidence behind it rather than being presented flatly as fact.
Whether naturally conditioned beer has a perceptibly finer carbonation than force-carbonated beer at the same level is disputed; what is not disputed is that bottle-conditioned beer contains live yeast that continues to scavenge oxygen.
— Widely repeated trade and enthusiast position that secondary fermentation produces smaller, finer bubbles and a softer mouthfeel.
— Carbonation level and dispense conditions determine bubble behaviour, and no controlled work establishes a difference attributable to the carbonation route itself at matched volumes.
BeerHQ separates the contested sensory claim from the uncontested functional one: live yeast measurably slows staling regardless of whether the bubbles differ.
Genuinely contested Credible sources disagree, so both positions are given rather than one.
Sources: Brewing: Science and Practice — print; Campaign for Real Ale