Water
Residual alkalinity
Hard water makes superb black beers and dull pale ones: residual alkalinity explains why.
Result
Fill in the values and run the calculation, or try the example.
This is the calculation Krausi uses. Create an account to save it in a recipe or a brew.
Create my accountWhy calculate residual alkalinity?
The bicarbonate in water resists the natural acidification of the mash. With pale malts, which are not very acidic, very alkaline water keeps the pH too high: extraction suffers, bitterness turns harsh and the beer lacks brightness.
Dark malts, on the other hand, are acidic: they make up for alkaline water. That is why Dublin, with its very hard water, became the city of stouts, and Pilsen, with its very soft water, the city of pale lagers.
Residual alkalinity sums up this suitability in one number, and tells you whether you need acid, salts or dilution.
How is residual alkalinity calculated?
Alkalinity comes from bicarbonate. Calcium and magnesium neutralise part of it during the mash: what is left is the residual alkalinity, according to Kolbach's formula.
alkalinity (ppm CaCO3) = bicarbonate × 50 / 61
residual alkalinity = alkalinity − calcium / 1.4 − magnesium / 1.7Guide values: below 0, the water suits very pale beers; from 0 to 50, pale and amber beers; above 100, brown and black beers.
Worked example
Values entered
- Bicarbonate in mg/L: 150
- Calcium in mg/L: 50
- Magnesium in mg/L: 10
Result from the tool
- Alkalinity in ppm as CaCO3
- 122.95
- Residual alkalinity in ppm as CaCO3
- 81.35
What the tool does not do
- It is a guide, not a pH prediction: the pH also depends on the malts.
- Measure the actual mash pH with a pH meter if you want fine tuning: the target is 5.2 to 5.6.
- Tap water analysis values vary over the year.
Frequently asked questions
My water is very hard, can I brew a pils?
Yes, by correcting it: cut it with reverse osmosis water to lower the bicarbonate, or neutralise the alkalinity with a little lactic acid. The two related tools do the maths.
What alkalinity for a stout?
A residual alkalinity of 100 to 200 ppm as CaCO3 suits black beers well: it offsets the acidity of roasted malts.
And with the assistant?
Ask Krausi the same question in plain language: he picks this tool, does the calculation and files the result in your project.
My water: 150 bicarbonate, 50 calcium, 10 magnesium. Can I brew a pale beer with it?
Your residual alkalinity is 81 ppm as CaCO3: a little high for a pale beer. Cut your water by half with reverse osmosis water, or add a few millilitres of lactic acid. Would you like me to calculate the dose?