Mash pH adjustment

What is actually happening

Mash pH is the variable that quietly decides whether everything else works. The enzymes that convert starch, the extraction of tannin from husk, the perception of bitterness and the clarity of the finished beer all depend on it, and the workable band is roughly 5.2 to 5.6 measured at room temperature.

Water alone rarely lands there. Alkalinity in the supply pushes it up; dark malts, which are acidic, pull it down — which is why a pale beer brewed with hard, alkaline water goes wrong in ways a stout brewed with the same water does not.

The corrections are lactic or phosphoric acid, acidulated malt, or calcium salts that react with the mash to release hydrogen ions. Calcium chloride and calcium sulphate both do that, and they pull the finished beer’s balance in opposite directions while they do it.

Getting it wrong at the alkaline end is what produces the harsh, drying astringency that reads as over-sparging, because both faults arrive by the same route: tannin extraction rises sharply as pH does.

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.
• Permanent haze — Cloudiness that does not clear with warming, usually from incomplete starch conversion or irreversible protein complexes.

Related steps and concepts

• Water treatment — Where the adjustment is usually planned.
• Mashing — The step it governs.
• Sparging — The other step where pH decides astringency.