Glossary
Mash pH
The acidity of the mash, conventionally targeted between about 5.2 and 5.6 measured at room temperature, and the single most consequential water-chemistry variable in brewing.
Enzyme activity, extraction efficiency, protein behaviour, hop utilisation and the harshness of dark malt all depend on it. A mash too alkaline extracts tannin and produces a dull, astringent beer; one too acidic produces a thin, sharp one.
The figure must specify its measurement temperature, because pH readings drift with heat by around 0.3 units between mash temperature and room temperature — quoting a target without saying which is a common source of confusion between brewers.
Related
- Alkalinity — The water property that most resists hitting the target.
- Burtonisation — The classic treatment for adjusting brewing water.
More vocabulary
ABV · ABW · Alcohol unit · Alkalinity · Alpha acid · Apparent attenuation · Attenuation · Beta acid · Cohumulone · Degrees Lovibond
See every term on the glossary index.
Last reviewed 2026-08-16.
Evidence
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Mash pH — conventionally targeted around 5.2 to 5.6 measured at room temperature — governs enzyme activity, extraction efficiency, protein behaviour, hop utilisation and how harshly dark malt expresses itself, and is the most consequential water-chemistry variable.
Backed by a source
Sources: Water: A Comprehensive Guide for Brewers — print; Brewing: Science and Practice — print
Mash pH readings drift with temperature by roughly 0.3 units between mash temperature and room temperature, so a stated target is meaningless without saying which measurement temperature it refers to.
Backed by a source
Source: Water: A Comprehensive Guide for Brewers — print