Understanding and controlling the water chemistry of your brewing liquor is essential to making excellent beer at high yields.

Step back 150 years and the reason why some water sources gave better beer at better yields was simply not understood. Certain cities became famous for the beers which worked out best with their water. Through a process of trial and error, brewers worked out which beer styles best suited the water they had available to them. London was noted for its’ Porter, Burton-on-Trent for pale hoppy beers (in those days meaning bitter rather than rich with hop oils), Dublin for Stout, Pilsen and Budweis for pale lagers and so on. In was only in 1850’s that a Dr Sheridan Muspratt speculated that the gypsum in Burton well water is what made it special. We had to wait until the early 20^th century before the full picture emerged and showed the importance of Calcium (Ca²⁺), Magnesium (Mg²⁺), carbonate (CO3^2-) sulphate (SO4^2-) and chloride (Cl^–) ions across multiple stages of the brewing process.

Some people think of water chemistry as too complicated and simply ignore it, but that approach means that both the brewer and the drinker miss out on a wide range of benefits from designing their brewing liquor composition correctly. So what are the main benefits?

• The pH in the mash is critical* and this is influenced by the alkalinity of the water which is increased by carbonate, but reduced by Ca²⁺ and Mg²⁺ ions {via the precipitation of Ca / Mg phosphate salts resulting in the release of hydrogen ions (H⁺)}

*In the mash you are using the power of enzymes such as α and β amylase to break down the barley starch into sugars. Enzymes are very sensitive to their environment, they work best within tight pH, temperature and reagent concentration windows.

• α-amylase is stabilised by calcium ions, and thus more long lived and effective when they are present at a sufficient concentration.

• Together this means that you will get a better extract yield with the correct calcium concentration in your brewing liquor. Darker beers need more calcium to compensate for their lower enzyme level too.

• Yeast health and flocculation is aided by calcium ions.

• We now know that it is not simply sulphate, but the sulphate to chloride ratio which is important in beer. This impacts which aspects of the beer are most prominent to the palate of the drinker. They are perhaps best thought of as seasoning. A high sulphate:chloride ratio (say 3:1) will express the bitterness where as a low sulphate:chloride ratio (say 1:2) will bring out the malty flavours.

The great news is, now that we understand the impact of water chemistry, we should be able to brew excellent beers of almost any style anywhere in the world simply by adding or removing the desired ions from the water to meet our needs. So now know the most significant benefits, what are we going to control and how are we going to do it?

Step 1 – understand the composition of your incoming water.

The best option is to have your water analysed for its “mineral” (dissolved ionic salts) composition. If you are using spring or well water this will be your only option. If you are buying a significant amount of brewing products from Murphy’s & Sons they will happily analyse your incoming water once a year for free. If not they offer this as a paid service for around £30. A very worthwhile investment.

If you are using mains / municipal water, another option is to search for the website of your local water company, most of them publish the ‘average composition’ of the water they provide by postcode. Expect water from rainwater catchment to be low in Ca and other dissolved salts, but ground water to be rather higher because of the salts dissolved from the rocks it has passed through.

Look out for elevated levels of Fe (> 0.5 ppm), Cu ( > 0.5 ppm), Mn (> 0.1 ppm) or nitrate (> 10 ppm) in your water too. If they are above these levels they will cause you flavour issues from day one, reduce your shelf life and impact your yeast health. If present at elevated, you will need to install an ion exchange column or related technology to reduce their level/s.

Step 2 – decide your ideal calcium, sulphate and chloride levels for the beer style

Style	[Ca] / ppm	Alkalinity (as ppm CaCO3)	[SO42-]	[Cl–]	SO4:Cl
Pale lager	50-75	0-40	0-150	50-100	1:1
Pale Ale	50-100	0-80	50-150	50-100	2:1
Amber Ale	50-150	80-200	50-150	50-150	1:1
Stout	50-75	80-160	50-150	50-150	1:2

They are quoted as ranges because (i) you usually have to work within the constraints of your raw water, which will already contain some of these ions, and (ii) you may need also to reduce the alkalinity of the water by the addition of calcium sulphate / chloride (see step 3). In most cases it would be impossible to hit precise values for all these aspects; fortunately experience shows that it is not necessary to be that precise.

Step 3 – calculate the total and residual alkalinity of your water.

Look for the ‘total alkalinity’ TA value (quoted as ppm CaCO₃), Ca and Mg levels in your water report. From these you can calculate the residual alkalinity RA you would expect in your mash.

RA = TA – ([Ca in ppm] / 1.4) – ([Mg in ppm] / 1.7)

Using this equation, check whether, with your first approximation of your planned calcium level, whether your RA will fall into range. If not, will it come in range if you increase the Ca level to near the top of the desired window? If the answer is still no, which is likely to be the case if you are making a Stout with soft water for example, then you will need to add some sodium bicarbonate (NaHCO₃) to increase the alkalinity without changing the calcium level. Experimental studies show that for every 10 ppm you want to increase the TA (in ppm CaCO₃ equivalent) you need to add 17 ppm NaHCO₃.

Step 4 – calculate the ratio of CaSO₄ to CaCl₂ you need to use.

The calcium that you add can be in the form of the sulphate or the chloride. Brewing textbooks will take you into the unique realm of milli-equivalents. But since I was a chemist before I was a brewer I’d suggest it’s easier just to look at the mass of each anion (sulphate or chloride) you want to use and calculate how much calcium this contributes. If you build a simple spreadsheet based on the following compositions / assays of the brewing salts it is quick and simple to adjust the levels iteratively until you get both your SO4:Cl ratio and [Ca] into range.

Salt	[Metal ion] / % w/w	[Anion] / % w/w
CaCl2.1.84H2O§	28.3	48.7
CaSO4 (gypsum)	29.5	70.5
MgCl2.6H2O§	12.0	34.9
MgSO4 (Epsom salts)	12.0	47.2
NaCl	39.3	60.7

^§Commercially available chloride salts are hydrates, they contain a small amount of water chemically bound within the structure.  77% CaCl₂ is the hydrate shown above. For simplicity in the main text I have not included the waters of crystallisation in the formulae.

I have included sodium chloride (NaCl) and the two magnesium (Mg) salts here too. If you have water which is already naturally high in calcium, it may not be possible to balance the SO4:Cl ratio without exceeding the desired total calcium level. In such cases you can add the required anion as the magnesium or sodium salt thus leaving the calcium level unchanged. Do note though that you should not exceed 100 ppm Na (starts to taste salty) or 15 ppm Mg (becomes a laxative!) if you do need to use these.

Worked example

We want to make a hop forward blonde ale…

Step 1 – find out the quality of the raw water

We get the following analysis back on the quality of our incoming mains water:

Component	Concentration
Alkalinity (TA)	140 ppm as CaCO3
Ca	80 ppm
Mg	3.2 ppm
Na	10.6 ppm
SO4	120 ppm
Cl	23 ppm

 

Step 2 – decide the ideal water profile for what we are making

For a hop forward blonde ale we would ideally required:

Component	Concentration
Alkalinity (RA)	50-100 ppm as CaCO3
Ca	50-100 ppm
SO4	50 -150 ppm
Cl	0-100 ppm
SO4:Cl	2:1

Since we want to make a hop forward style we will malt to suppress the malt flavours to showcase the hops so we would look for a high SO4:Cl ratio, let’s assume we aim for 2:1.  Also let’s clarify here, this is the ratio of the weight of sulphate to the weight of chloride, it’s as simple as that (no reason to be thinking about moles or milli-equivalents)

 

Step 3 – Calculate the residual alkalinity (RA) at the desired [Ca]

The calcium level in our water is already within the desired range, so we would calculate the RA based on the raw water itself.

RA = TA – ([Ca in ppm] / 1.4) – ([Mg in ppm] / 1.7)

RA = 140 – (80 / 1.4) – (3.2 / 1.7)

RA = 79.7 ppm as CaCO₃

This too falls within our target range.

 

Step 4 – calculate the ratio of CaSO₄ to CaCl₂ you need to use.

The level of sulphate in our water is already high but the chloride low, the ratio of SO4:Cl being 5.2:1. Thus we are going to need to add a chloride salt to reduce this ratio. We have two options, we could add CaCl₂ to get our 2:1 ratio but the resultant [Ca] would then be 101 ppm and the new RA = 66 ppm as CaCO₃. The Ca level would be only just outside the desired range so that would probably be acceptable. Another option would be to add the chloride as NaCl which would leave the [Ca] and RA unchanged. Let us look at how we calculate this addition.

Desired [Cl] = 60 ppm

Current chloride conc. = 23 ppm

Need to increase [Cl] by 60 – 23 = 37 ppm

Using the table above we note that NaCl is 60.7% Cl so the additional [NaCl] required to achieve this is:

37 ppm / 60.7% = 61 ppm NaCl

Finally let’s check that this does not take the total [Na] above 100 ppm.

Na contribution from 61 ppm NaCl

= 61 x 39.3% Na

= 24.0 ppm Na

Total [Na] = contribution from raw water plus contribution from added NaCl

= 10.6 + 24.0 = 34.6 ppm.

So we have our answer, because we already have a gypsum rich water supply we need only add 24 ppm, or 24 mg per litre, of NaCl to get the ideal brewing liquor for our blonde ale.

If you would like more help with water chemistry, contact me and we can look at it together.