Calcium Carbonate (Chalk) - 500g

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