When I bought a digital pH tester last year I knew at the time that in order to continue getting the most accurate pH measurements possible, a small amount of regular maintenance would be needed. The way I look at it having to recalibrate a pH tester once a month is a pretty small inconvenience compared to the benefits that an accurate pH reading will provide. Recalibrating a pH tester isn’t hard to do, the entire process takes less than ten minutes and can even be fun once you get started. Just like all of the other gear in my brew room I feel like I never get to use my meter often enough, so recalibrating it every month gives me a chance to use it more often in between brew days.
The Hanna HI98121 pH tester I use requires calibration using buffer solutions of pH 4.01, 7.01 and optionally 10.01, but there are other pH meters on the market that require 4.0, 7.0 and 10.0 buffer solutions for calibration. I bought the buffer solutions in the large economy sizes when I ordered the meter, there’s 25 packets in each box and so far they’ve lasted a good long while. I calibrate my pH meter for use in the brew room using the 4.01 and 7.01 buffer solutions because most of the pH measurements taken will be recorded within that pH range. I usually target the 5.4 to 5.6 pH range when preparing my brewing water at room temperature and the finished beer typically measures in the 4.3 to 4.5 pH range.
To begin the calibration process I pour the contents of each of three buffering solutions into plastic cups marked 4.01, 7.01 and 10.01. Pressing the ‘Mode’ button on the meter one time turns the meter on and runs a battery check, once the battery check has completed pressing the ‘Mode’ button again and holding it in puts the meter into calibration mode and the meter will display ‘CAL’. Once ‘USE’ is displayed followed by ‘7.01’ I dip the bulb of the tester into the 7.01 buffer solution and swirl it around a little until ‘REC’ is displayed. At this point the meter is recording the pH reading that it gets from the buffering solution and storing it as the 7.01 reference for use when taking pH readings later. The meter then displays ‘USE’ and followed by ‘4.01’ and I dip the bulb of the tester into the 4.01 buffer solution. The meter then measures the pH of the buffer and displays ‘REC’ again as it stores the reading as the 4.01 reference for later use.
In addition to performing monthly maintenance calibrations a pH meter should also be calibrated right before taking pH readings in order for it to provide the most accurate measurements. Before adjusting my brewing water’s pH, or making any salt and mineral additions, I first take a few minutes to calibrate my meter. Brewing water preparation begins by filling a clean cooler with reverse osmosis water made the night before brewday and measuring its pH using a calibrated meter. Interestingly enough, since freshly filtered RO water has had all of its salt and minerals removed, it will easily absorb Co2 from the surrounding air which results in an increase in acid that will lower the pH reading of the water.
Using salt, mineral, acid and/or base additions as needed the pH of the brewing water is easily adjusted to be within the 5.4 to 5.6 pH range at room temperature. Once the pH range has been set the alkalinity of the brewing water can be adjusted so that it’s buffering is most resistant to change between 5.2 to 5.4 pH at around 150F. This is done by adjusting the brewing water levels of calcium, magnesium, sodium and chloride to match those of the beer style being brewed.
I like using EZwatercalculator to figure out what additions need to be made to my brewing water for it to be most suitable to the style of beer I’m brewing. Used with a well maintained pH meter the two provide a powerful tool for accurately building the best brewing water profiles. Unlike temperature there’s no way to stick a finger into your brewing water to determine its pH value, a meter is needed for that. EZwatercalculator takes the guesswork out of determining the additions, readily available at any LHBS, that will be needed to create the perfect water profile for any style of beer. Before setting out to brew your next batch of beer you too may also want to spend a little time testing the waters.