Build alkaline water for dark beers.
Chalk (calcium carbonate, CaCO₃) raises residual alkalinity and mash pH — exactly what you need when dark, acidic malts would otherwise drive the mash too low. The classic addition for stouts, porters and other dark styles that want a carbonate concentration of at least ~150 ppm.
What it does
- Raises residual alkalinity and mash pH
- Counters the acidity of dark, roasted malts
- Adds calcium and carbonate to soft water
Dosing & tips
Roughly 1 g of CaCO₃ per litre contributes around 400 ppm Ca²⁺ and 600 ppm total alkalinity (as CaCO₃). Carbonate targets are about 25–50 mg/L for pale beers and 100–300 mg/L for dark beers. Chalk has low solubility in water, so it works best added directly into the mash rather than the brewing liquor.
Use a water tool (BeerSmith, Brewfather, RAPT) to calculate exact additions for your target profile.
To lower pH instead, see Lactic Acid · Weigh accurately with our pocket scales · See all Cleaning & Ingredients
Specifications
| Compound | Calcium carbonate (CaCO₃) |
| Effect | Raises residual alkalinity & mash pH |
| Best for | Dark beers (stouts, porters) |
| Pack size | 500 g |