mashing
Water treatment
Adjust the mineral content and alkalinity of brewing water so the mash reaches a workable pH and the finished beer has the intended balance.
Also called liquor treatment, brewing water adjustment.
What is actually happening
Alkalinity is dealt with first, because it is what prevents the mash reaching a workable pH. It can be reduced by boiling, by dilution with deionised water, or by acid addition.
Calcium is added — usually as gypsum or calcium chloride — to lower mash pH, support enzyme and protein behaviour, and help yeast flocculate. Which salt is chosen sets the sulphate-to-chloride balance and therefore whether the beer reads crisp and dry or full and round.
The order matters and is often reversed in popular accounts, which treat water treatment as a flavour exercise. It is a chemistry exercise first; the flavour effects are real but secondary.
What goes wrong here
Risks rather than certainties. This step does not cause these faults; getting it wrong can.
- Astringency — A drying, tannic harshness from over-extracted grain husk — the classic sign of sparging too hot, too long or at too high a pH.
- Chlorophenol — A medicinal, sticking-plaster note formed when chlorine meets phenols — almost always a cleaning or water-treatment failure.
- Metallic — A coin-like metallic note, usually from corroded equipment or high-iron brewing water.
Questions
Does adding gypsum make beer more bitter?
Not directly. Sulphate contributes no bitterness of its own; it changes how the bitterness already present is perceived, accentuating it and drying the finish. Overdone, it reads as harsh and minerally rather than as more bitter, which is why heavy Burtonisation is easy to get wrong.
Do I need to treat my water at all?
It depends entirely on your supply and what you are brewing. A moderately alkaline water brewing a dark beer may need nothing; the same water brewing a pale lager will produce a dull, harsh result without treatment. Removing chlorine or chloramine is worth doing regardless, because both produce medicinal chlorophenols.
Related steps and concepts
- Alkalinity — The property treated first.
- Mash pH — The target.
- Burtonisation — The classic named treatment.
Also at the mashing stage
Decoction mash · Infusion mash · Kettle souring · Mash pH adjustment · Mash-out · Mashing · Sour mashing · Step mash · Turbid mashing
See the whole process in order on how beer is made.
Last reviewed 2026-08-16.