Glossary · Chemistry
Carbon dioxide
Also written CO2. Each is a name for the same thing, which is why none of them has an entry of its own.
Definition
The gas produced alongside ethanol in fermentation, and the gas that makes a cider sparkle. Its solubility falls as temperature rises, which is why a warm bottle foams.
- Subject
- Chemistry
- Also written
- CO2
In more detail
Carbonation is quantified in volumes — the volume of gas, at standard conditions, dissolved in one volume of liquid. A still cider holds well under one volume, a pétillant one to two, and a fully sparkling cider three or more. Dissolved carbon dioxide also lowers pH slightly and sharpens the perception of acidity.
Where this is covered properly
The glossary defines; these pages explain. Each is described in its own words.
Related terms
Terms that belong to the same part of the subject, or that this one is routinely confused with.
Cider
Sparkling
Carrying enough dissolved carbon dioxide to form a persistent bead and a distinct prickle, whether from bottle conditioning, tank conditioning or injected gas.
Cider
Pétillant
Lightly sparkling — enough dissolved gas to prickle on the tongue but well below the pressure of a fully sparkling cider, typically the result of a slow, incomplete secondary fermentation.
Fermentation
Forced carbonation
Dissolving carbon dioxide into finished cider under pressure, in tank or in line, rather than generating it by fermentation.
Fermentation
Priming
Adding a measured quantity of fermentable sugar at bottling or kegging so that a residual yeast population produces carbon dioxide in the sealed container.
Sensory
Mousse
The foam a sparkling cider forms when poured, and its persistence. Fine, long-lasting mousse is associated with bottle conditioning; coarse, quickly collapsing foam with injected gas.
Where to go next
- Cider glossary — The whole vocabulary, by subject and A–Z.
- Comparisons — Terms that are only really clear when set against the thing they are not.
- Search — Finds terms by their aliases and by their spellings in other languages.
Sources
What this page rests on. Where a source is marked as registered rather than read, CiderHQ is recording that the body is authoritative on the subject without claiming to have worked through the document itself. See our evidence policy for what each state means.
The New Cider Maker’s Handbook: A Comprehensive Guide for Craft Producers
Claude Jolicoeur, Chelsea Green Publishing, 2013. ISBN 9781603584739 · reference work · bibliographic record verified, not opened 2026-08-25
Bibliographic record verified on 2026-08-25 against the Open Library union catalogue: Chelsea Green Publishing, 2013, ISBN 9781603584739, one edition recorded. That establishes the citation points at a real book in a stated edition, which is what a citation needs and is all it establishes. No copy was opened and nothing is quoted from it. The book itself is in print and not digitised in any open collection; where CiderHQ needs a figure from this territory it uses an accessible research source instead and says so.
Cider and perry production technical training material
Peter Mitchell / Cider and Perry Academy · reference work · registered as competent for this subject
Searched again on 2026-08-25 and it remains the one printed source here that a bibliographic check cannot fix, because it is not a published work with an edition. It is course material issued to participants of a training programme, so there is no catalogue record to verify, no ISBN, and no lawful public copy. Its state stays `registered` for that reason rather than through inattention.