Glossary
Alkalinity
A water’s capacity to resist acidification, driven principally by bicarbonate, and the property that determines whether a given grist can reach a workable mash pH.
Also called residual alkalinity, carbonate hardness, temporary hardness.
Alkalinity is why alkaline-water cities historically brewed dark beer. Roasted and crystal malts are acidic; in high-bicarbonate water they bring the mash down to a workable pH, whereas a pale grist in the same water sits too alkaline and produces harsh, dull beer.
Residual alkalinity refines the idea by accounting for calcium and magnesium, which push pH the other way. It is the figure a brewer actually works with when treating water.
Related
- Mash pH — What alkalinity is managed in order to control.
- Dublin water — A classic high-alkalinity supply, and the stout tradition around it.
- Pilsen water — The opposite extreme — water so soft it suits the palest grist.
More vocabulary
ABV · ABW · Alcohol unit · Alpha acid · Apparent attenuation · Attenuation · Beta acid · Cohumulone · Degrees Lovibond · Degrees Plato
See every term on the glossary index.
Last reviewed 2026-08-16.
Evidence
What BeerHQ knows about this, and how. Every statement carries the state of the evidence behind it rather than being presented flatly as fact.
Calcium lowers mash pH, supports enzyme and protein behaviour, assists yeast flocculation and improves clarity, and is very nearly flavour-neutral — which makes it the ion most brewing water is actually adjusted for.
Backed by a source
Sources: Water: A Comprehensive Guide for Brewers — print; Brewing: Science and Practice — print