Jim's Beer Kit

Alkalinity Measurement and Adjustment

One of the most important things we need to know, before we start throwing chemicals at our liquor, is a measurement of the alkalinity, and less importantly calcium, in the liquor to start with. Once upon a time, water boards were really helpful, and actually published the alkalinity value on their water schedule. Unfortunately since privatisation, and 'regulation' they are no longer doing so, and trying to get a figure out of a water company is akin to extracting your own teeth, without anaesthesia, painful and fundamentally futile. So how can we as brewers easily determine the level of these ions in the brewing liquor?

Alkalinity and Beer Style

The problem with alkalinity is that it is prevents the mash pH from falling in the right range, and it is much more effective at preventing the reduction in pH than calcium is in causing it to fall. Therefore in order to ensure a proper pH through out the brewing process we need to ensure that the alkalinity of our liquor is suitable for the beer style being brewed. Beers made with al all pale malt grist should not have alkalinity greater than 25mg/L, as more dark malts are added to the grist, then the alkalinity level can be allowed (indeed increased in some water areas) to rise up to around 100mg/L for porters and stouts. This is because of the acid nature of the roast malts offsets the alkalinity to a considerable degree. High wort pH (through high alkalinity) introduces harsh tastes in the finished beer, Beta amylase activity is lowered leading to poor efficiency, Increased possibility of sparging polyphenols and tannins , Reduced hot break formation in the kettle, Hop utilisation is increased , poorer fermentation due to lower levels of Free Amino Nitrogen, bacteria are more active in high pH wort. All of these contribute to a lower beer stability, which can introduce hazes, the colour will be darker and flavour poorer.

Measuring Alkalinity

Alkalinity is determined by the concentration of the bicarbonate (more properly hydrogen-carbonate, HCO3-) ion, and can be measured very simply by measuring the amount of, a known concentration of, acid required to reach a pH of 4.5 which is where all the bicarbonate is converted to water and CO2. Conveniently brewers have access to an acid of known concentration from Brupaks known as Carbonate Reducing Solution, and all that is required is access to a pH meter or a 0.04% solution of methyl orange indicator solution. Unfortunately for most brewers these are quite difficult to find for a sensible sum or sensible amount. One litre of methyl orange would last most brewers a couple of lifetimes, and an accurate pH meter will set you back around £ 150- £ 200. An alternative method which has come to light courtesy of Jims Beer Kit, is the Salifert KH and Alkalinity test kit, used for measuring the alkalinity in aquaria. (Other test kits are available but the Salifert test gives the results in a measurement that we can use, and has proved to be the most accurate)

The Test Kit

Using the alkalinity test kit is simplicity itself (see also the pictorial guide on the next page). 4ml of the liquor is added to a test tube (supplied), using the supplied syringe. Then 4 drops of the supplied indicator is added which turns the water blue/green. Using the small (supplied) syringe with the fine tip you then add the KH solution, drop wise, swirling the test tube between drops, and eventually there is a colour change, through blue/grey to purple and eventually pink. Although the kit instructions say that you measure the value when it is pink the actual end point is closer to a pinky purple as shown in the picture. Another thing to note, and not worry about, is that as you approach the end point you will get a colour change which will then fade back to the original colour as you swirl the tube, this is normal and you should continue to add solution and swirling until the colour change is permanent.

You then simply read the value off of the syringe at the position of the black plunger, which in this case is 0.95, and look the value up in a table. The table supplied with the kit gives the values in milliequivalents per litre (mEq/L) and to get these into a 'useful' value you multiply by 50 to get the alkalinity as mg/L calcium carbonate. 0.95 is about 0.34mEq/L which multiplied by 50 is 27mg/L calcium carbonate; perfect for pale beers with no requirement to reduce the carbonate further. By contrast a sample of water taken on the Isle of Wight in 2008 had a reading of 0.17, which reading from the supplied table gave an alkalinity of 4.8mEq/L, multiply by 50, giving an alkalinity of 242mg/L calcium carbonate. If this water was to be used for brewing the alkalinity must be reduced before use either by boiling or using acids. Table 1 has been compiled to allow the direct reading of alkalinity as calcium carbonate from the reading on the syringe.

Interpreting the Results and Making Adjustments

Having measured the alkalinity, how does this help. In the ideal world the alkalinity would be reduced to the correct level for the beer style being brewed. For pale beers this should be around 25mg/L or below, for darker beers then up to 75mg/L is acceptable and for stouts and porters it can be as high as 100mg/L. Traditionally alkalinity has been reduced by boiling, which drives off carbon dioxide and leaves behind calcium carbonate or lime scale. However this is time consuming and expensive, and eventually someone has to get into the HLT and scrape the scale from the floor of the vessel and from the elements. It is also very difficult to remove the last 50mg/L calcium carbonate from the liquor, and robs the liquor of desirable calcium. A more effective method is to add a calculated amount of acid to the liquor. This also drives off the CO2 and adds a small amount of useful anions to the liquor. The easiest acid to acquire and use is Carbonate Reducing Solution (CRS) from Brupaks, which is a blend of hydrochloric and sulphuric acids. 1ml of CRS removes 183mg of alkalinity and adds 56mg of chloride and 89.6mg of sulphate, it also has the useful benefit of leaving any calcium in the liquor untouched.

Looking at the Isle of Wight liquor above, if it was wanted to brew a pale ale then 217mg (242-25) of alkalinity would have to be removed from all the liquor used for brewing, typically 30L for a 5 gallon brew length. So a total of 6510mg of carbonate (217*30) has to be removed, requiring the addition of 35.5ml of CRS (6510/183). Typically this would be done in two additions, two thirds of the amount would be added as the liquor was being drawn off (the agitation helps dissipate the carbon dioxide), and then the alkalinity would be measured again and the final amount to be added recalculated. This technique helps prevent the over addition of CRS which would potentially drive the mash pH too low.

Measuring the alkalinity of the liquor is probably the single most important measurement that can be made by brewers, as it enables us to determine exactly just how much the alkalinity needs to be reduced to ensure that the mash pH has a good chance of falling in the right range. This will have the effect of making the beers last longer and have cleaner, brighter flavours.

Table 1 - Conversion between syringe reading and alkalinity

(Note - these figures can change if the manufacturer updates the design of the kit - please check the instructions provided with your particular test kit)

Reading in ml	Alkalinity mg/l Calcium Carbonate	Reading in ml	Alkalinity mg/l Calcium Carbonate
0.98	16	0.48	154
0.97	21	0.46	159
0.94	27	0.44	165
0.92	32	0.42	170
0.90	38	0.40	176
0.88	43	0.38	181
0.86	49	0.36	187
0.84	54	0.34	192
0.82	60	0.32	198
0.80	65	0.30	203
0.78	71	0.28	209
0.76	76	0.26	214
0.74	82	0.24	220
0.72	87	0.22	225
0.70	93	0.20	231
0.68	98	0.18	236
0.66	104	0.16	242
0.64	110	0.14	247
0.62	115	0.12	253
0.60	121	0.10	258
0.58	126	0.08	264
0.56	132	0.06	269
0.54	137	0.04	275
0.52	143	0.02	280
0.50	148	0.00	286

Thanks to Aleman for the text on this page.