Although perfectly good beer can be made without considering your mash pH, having an understanding of the cause and effect of correct pH on the mash will help improve your brewing.

What is pH?

pH is the measure of the acidity or alkalinity of a liquid. Neutral pH is considered as 7, which is the pH of pure water. Most tap waters will run somewhere around 7 or higher depending on how hard the water is.

pH is measured using strips or a digital pH meter. Although strips are adequate as a guide, they are hard to read so it’s well worth investing in a proper pH meter for accurate results. These are relatively expensive and also require careful handling as the probes are very delicate but they can also be used to measure fermentation pH, useful for all brewing but essential for sour beers.

pH and the Mash.

The ideal mash pH range is considered to be between 5.2 and 5.5. Mash pH is different from the pH of your water as the malts are acidic so they will lower the pH once added to the water.

Having the correct pH will:

- Improve enzyme activity during the mash.  This will increase conversion of starches to fermentable sugars.

- Lower pH in the finished wort. Improving yeast health during fermentation and inhibiting bacteria growth.

- Improved hop extraction rates in the boil and giving smoother bitterness.

- Better protein and polyphenol precipitation both during the cold break and post fermentation.

- Improved clarity in the finished beer with reduced chill haze.

- Improved flavour and clarity stability as the beer ages.

Factors effecting mash pH

Although mash pH can be predicted it can be difficult to accurately predict so measure and then adjust on subsequent brews.

The two main factors affecting your mash pH are water and malt.


A general rule of thumb is hard water will be more alkaline leading to increased mash pH. Softer water will be more acidic and therefore decrease the effect on mash pH. This is not quite as straight forward as just measuring the water’s pH as it is the alkalinity of the water (usually measured in CaC03) and it’s mineral content that will dictate the effect on pH.  You can purchase test kits to measure the alkalinity but you will also need to know the calcium and magnesium content to more accurately predict the effect on the mash pH. Most water requires some treatment when brewing pale beers to ensure the mash remains around 5.2.

Grist make up

Malt is acidic. The malting and heating process causes the acidity to increase and therefore darker malts will lower the mash pH even more. If you have high alkaline water then you may well be able to brew dark beers without having to do anything to lower the pH. In fact you may need to increase the pH if you are brewing dark beers in soft water areas.

Measuring and adjusting

A digital pH meter is the best method of measuring pH. You need to cool the sample to around 20c before you measure the pH as temperature affects pH and the ideal range 5.2 – 5.5 is measured at room temperature. High temperatures will also damage the probe.

There are several options for adjusting the pH.

-       Acid (usually food grade lactic or mixed acid like AMS) can be added to the water to reduce pH.

-       Dark malts or Acid malts can be added to reduce pH.

-       Reverse osmosis water can be used in full or as a dilution to decrease the mash pH.

-       Calcium or magnesium bearing salts like gypsum can be added although these will also alter the mineral composition so could have negative effects if not monitored.

-       Water can be pre boiled to reduce the hardness.

I will cover water chemistry in more detail as that is a blog post on it’s own but hopefully you now have a fuller understanding of the importance of correct mash pH.

If you know the make up your water you can use a water calculator to help predict mash pH based on your malt make up. This will then calculate any water treatments required.

For an easy solution, a water analysis from Murphy’s does all the hard work for you. Giving you the mineral make up of your water, alkalinity and recommended additives based on Pale, Dark and lager styles to ensure correct pH and mineral profile.