Glossary · Fermentation
Attenuation
Also written degree of attenuation, apparent attenuation. Each is a name for the same thing, which is why none of them has an entry of its own.
Definition
The proportion of the original sugar that fermentation has consumed, calculated from the fall in gravity from the starting to the current reading and expressed as a percentage.
- Subject
- Fermentation
- Also written
- degree of attenuation, apparent attenuation
In more detail
Apparent attenuation is calculated from hydrometer readings and overstates the true figure, because ethanol is less dense than water and drags the final reading below the density that the remaining sugar alone would give. That is why a fully dry cider finishes below 1.000. Real attenuation, corrected for alcohol, requires distillation or an instrument that separates the two.
In cider the practical use is diagnostic: an attenuation that stalls well short of dryness signals a nitrogen shortage, a temperature problem or a stressed yeast, and identifies a stuck fermentation before the tank starts smelling of it.
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.
Chemistry
Specific gravity
The density of a liquid relative to water at the same temperature. In cider it is the routine measure of dissolved sugar before fermentation and of progress during it.
Chemistry
Residual sugar
The fermentable sugar remaining in a finished cider, usually expressed in grams per litre. It is what sweetness legislation and style bands are written against.
Fermentation
Stuck fermentation
A fermentation that has halted before the sugar is used up and will not restart on its own. It is distinct from a deliberately arrested ferment and from a merely sluggish one.
Cider
Dry
A cider or perry with little or no residual sugar, in which fermentation has taken the sugars essentially to completion.
Chemistry
Potential alcohol
The alcoholic strength a juice would reach if all its fermentable sugar were converted, estimated from the starting gravity.
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.
Cornell Cider Research and Extension programme
Cornell University, School of Integrative Plant Science · university · passage verified 2026-08-24
Runs cultivar trials in New York State and publishes juice chemistry for European cider varieties grown in a North American climate — the single most useful counterweight to treating English figures as universal.