Glossary · Equipment
Hydrometer
Also written saccharometer. Each is a name for the same thing, which is why none of them has an entry of its own.
Definition
A weighted float whose depth of immersion indicates the density of a liquid, used to read specific gravity before and during fermentation.
- Subject
- Equipment
- Also written
- saccharometer
In more detail
Readings are taken in a trial jar rather than in the vessel, and must be corrected for temperature against the instrument’s calibration point. A hydrometer measures density, not sugar: once alcohol is present the reading reflects both, which is why final gravities fall below 1.000.
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.
Equipment
Trial jar
A tall narrow cylinder in which a sample is held for a hydrometer reading, deep enough for the instrument to float clear of the base and narrow enough to need little juice.
Equipment
Refractometer
An optical instrument that measures the refractive index of a drop of juice and reads it out as degrees Brix. Accurate on unfermented juice and unreliable once alcohol is present.
Fermentation
Attenuation
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.
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.