Which acid should I use?
If your water carries much alkalinity, malt alone often can’t pull the mash into range and you reach for acid. Every acid moves pH the same way: its hydrogen ions neutralize bicarbonate. What differs is the anion left behind and the flavor that rides in with it. For almost everyone the real choice is just lactic or phosphoric; the rest are situational.
The two you’ll actually use
Lactic acid (88%) is the homebrew default: cheap, safe to handle, effective in small doses. It leaves lactate behind, which tastes tart only when you add a lot; the commonly cited threshold is around 400 ppm lactate, and Troester’s own tasting panel found it hard to detect below that. In practice the tang shows up only when very alkaline water forces a large dose. It’s the right pick for small-to-moderate corrections, and a natural fit for German styles where a faint tang is at home.
Phosphoric acid (10%) is the flavor-neutral option. It leaves phosphate, an ion already abundant in wort from the malt, so a normal dose is essentially undetectable. Reach for it in pale, delicate beers (Pils, Helles, Kölsch), and whenever the dose is large enough that lactate would become tasteable. It’s also the usual choice for acidifying sparge water, where there’s no grain buffering to hide behind. One caveat: at high strength (75–85%) it’s sold concentrated and needs careful dilution.
A useful way to think about it: lactic and phosphoric let you set pH and set your sulfate and chloride separately with salts. The next group ties those two decisions together.
The flavor-ion acids: sulfuric, hydrochloric, CRS
Sulfuric leaves sulfate (accentuates hop bitterness, dry finish); hydrochloric leaves chloride (rounds and fills). So they cut alkalinity and push your water toward hoppy or malty at the same time. The problem is safety: both are far more aggressive and can form harmful mists, which is why they’re rarely recommended for homebrewers and never worth it without food-grade acid and proper protection. Most brewers reach the same sulfate or chloride goal more safely with gypsum or calcium chloride plus a gentler acid.
CRS/AMS is a UK product, a ready-made sulfuric-plus-hydrochloric blend for stripping alkalinity while adding sulfate and chloride together in a fixed, roughly sulfate-leaning ratio (the exact split depends on the formulation, and Murphy & Son revised theirs in 2025). It’s convenient when that ratio suits your beer. The catch, and the thing Martin Brungard has long flagged, is that the ratio is fixed: on high-alkalinity water a large correction forces large additions of both ions at once, which can push the water into minerally territory whether you wanted those levels or not. If you specifically want one ion and not the other, a single acid serves you better. Apply it to all your liquor, not just the mash.
Acid malt: acid you can weigh
Acidulated malt (Sauermalz) is Pilsner malt treated with lactic acid, so you dose it by weight like any grain, with no liquid to measure or spill. Rule of thumb: each 1% of the grist drops mash pH about 0.1, and most brewers stay at or under ~5%. It’s mash-only, can only lower pH, and is less precise than liquid acid, but it’s forgiving and it’s the classic Reinheitsgebot-friendly route. Weyermann lists it at 1–2% lactic acid by weight; note that brewing calculators often model it at ~3%, which is its total acid equivalence rather than its physical lactic content, so the two figures you’ll see aren’t a contradiction.
The specialty acids: citric, malic, tartaric, acetic
These four carry distinct flavors, which makes them the wrong tool for routine, invisible pH correction but the right tool when that flavor is part of the beer. All are available in the calculator.
- Citric brings a lemony, citrus-peel note. It’s a natural choice in fruited and citrus-forward styles, and it pairs well where you want a bright, zesty edge to read as intentional. Worth knowing: some yeast can convert citrate toward acetic acid, so it’s better added late or in beers where a little acidity development is welcome.
- Malic gives a crisp green-apple tartness. It shows up in fruit beers (especially apple and stone-fruit character) and wine-inspired hybrids, and it’s the acid to reach for when you want tartness that reads as fruit rather than dairy.
- Tartaric is the sharpest of the group, with a clean, sometimes grape-like or minerally bite. It’s the classic winemaking acid, so it’s at home in grape-adjacent and wine-barrel beers where you’re deliberately borrowing that character.
- Acetic is vinegar. Used sparingly it’s a defining, welcome note in Flanders reds, oud bruins, and other sour and wood-aged styles; the only caution is that its flavor threshold is low, so dose small and taste as you go.
For plain alkalinity reduction in a clean beer, lactic and phosphoric are still the easier path. But when you’re building a flavor rather than hiding one, these are exactly what you want.
FAQ
Lactic or phosphoric?
Phosphoric when you want zero flavor impact or need a big dose (pale beers, sparge water); lactic for small corrections or where a slight tang is welcome. Below their thresholds both are undetectable, so for modest doses it rarely matters.
How much acid does it take?
Not much: malt is a strong buffer, so a few milliliters of concentrated acid moves a typical mash. That’s exactly why you dose to a prediction and confirm with a meter rather than eyeballing it.
Is the “strength” number on the bottle important?
Very. A 10% and an 85% bottle of the same acid differ nearly ninefold per milliliter. Always tell your calculator the exact strength in hand; “5 mL of lactic” and “5 mL of phosphoric” are not the same dose.
Any safety rules?
Always add acid to water, never water to acid, and dilute the concentrated stuff. Use food-grade product only, and give sulfuric and hydrochloric real respect (goggles, gloves, ventilation). Even 88% lactic will burn eyes and skin.
Anion and flavor behavior follows Kai Troester, “Mash pH control” (braukaiser.com) and the lactate-threshold experiment; Palmer & Kaminski, Water (2013); Weyermann’s acidulated malt specification; and Murphy & Son’s AMS data sheet. Acid strengths and dose math are verified in brewwtr’s test suite.