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Water

Acid dose to neutralise alkalinity

5 mL of lactic acid in 30 L of sparge water, and the astringency is gone. The tool gives the dose for your volume and your alkalinity.

Lactic 88%, phosphoric 75% or phosphoric 10%.

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.

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Why acidify your brewing water?

Alkaline water causes two problems. During the mash, it keeps the pH too high for pale beers. During the sparge, it extracts tannins from the grain husks: that is astringency, the feeling of over-brewed tea.

A few millilitres of acid neutralise the bicarbonate and solve both. Lactic acid at 88% is the most common; phosphoric acid is more neutral in taste.

These are corrosive products: gloves, goggles, and always acid into water, never the other way round.

How is the acid dose calculated?

The alkalinity to neutralise is converted to milliequivalents, then divided by the strength of the acid:

mL of acid = alkalinity (ppm CaCO3) / 50 × volume (L) / strength (mEq/mL)

Strengths used: 11.8 mEq/mL for 88% lactic acid, 12.1 for 75% phosphoric acid, 1.07 for 10% phosphoric acid.

The alkalinity to neutralise comes from the residual alkalinity calculation.

Worked example

Values entered

  • Volume of water in litres: 30
  • Alkalinity to neutralise in ppm as CaCO3: 100
  • Acid: Lactic acid 88%

Result from the tool

Volume of acid in mL
5.08 mL
Milliequivalents neutralised
60
Acid strength in mEq/mL
11.8 mL

What the tool does not do

  • The tool does not predict the resulting pH: it neutralises an amount of alkalinity.
  • Above 2 to 3 mL of lactic acid per 10 L, its taste may be noticeable in a light beer.
  • The actual concentration of an acid opened long ago may have changed.

Frequently asked questions

Lactic or phosphoric acid, which should I choose?

Lactic acid at 88% is easy to find and to dose. Phosphoric acid cannot be tasted, even at a high dose: prefer it for very alkaline water or a delicate beer.

Should I acidify the sparge water?

Yes if your water is alkaline: it is the simplest way to avoid astringency. Aim for sparge water with no alkalinity, or a pH below 6.

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.

I have 30 L of sparge water with 100 ppm of alkalinity, how much lactic acid?

Add 5.1 mL of 88% lactic acid to your 30 L. With 75% phosphoric acid, it would be 5.0 mL. Wear gloves and pour the acid into the water.

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