Glossary
Hydrometer
A weighted glass float that measures specific gravity by the depth at which it settles in a liquid.
Cheap, accurate and unaffected by alcohol, which is its advantage over a refractometer for post-fermentation readings. Its disadvantage is that it needs a substantial sample, which must be drawn from the fermenter and is normally discarded.
Readings need correcting to the instrument’s calibration temperature, usually 20 °C. A hot sample reads low.
Related
- Specific gravity — What it measures.
- Refractometer — The alternative instrument, and its alcohol problem.
More vocabulary
Beer engine · Coolship · Foeder · Kettle · Lauter tun · Mash tun · Refractometer · Sparkler
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Last reviewed 2026-08-16.