Glossary
Cask
A sealed container in which beer completes its fermentation and from which it is served without added gas pressure.
The full record
Cask has its own catalogue entry with the detail this page summarises — causes, thresholds, related styles and evidence.
Cask — A vented container in which beer finishes fermenting and from which it is served — a live product with a working life of days.
What distinguishes a cask from a keg is not its shape but what is happening inside it. Cask beer arrives unfinished: live yeast and residual fermentable material remain, and the secondary fermentation in the cellar produces the beer’s gentle natural carbonation.
As beer is drawn off, air replaces it. That is why a broached cask has a service life measured in days rather than weeks, and why cellar management is a real skill rather than a formality.
Related
- Keg — The sealed, gas-pressured alternative.
- Cask conditioning — What happens inside it.
- Firkin — The standard size.
- Cask — The packaging record.
More vocabulary
Beer-clean glass · Brewer’s barrel · Cellar conditioning · Crowler · Draught · Firkin · Growler · Imperial pint · Keg · KeyKeg
See every term on the glossary index.
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.
The vented cask that gives real ale its character is also its weakness: a 2024 review reports a study finding 46% of the microflora isolated from cask ale samples to be acetic acid bacteria, which need the oxygen and warmth that cask dispense supplies.
Checked against the source
Source: Roselli et al., "The two faces of microorganisms in traditional brewing and the implications for no- and low-alcohol beers" (2024), Acetic acid bacteria, under anaerobic gram-negative spoilage bacteria (Front Microbiol 15:1346724)