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Test Equipment, Tools and Equipment
How to Calibrate and Use a pH Meter for Brewing (Complete Guide)
Calibrating your pH meter is an essential part of getting accurate readings.
Brewers, winemakers, and distillers need to maintain the right balance of acidity and alkalinity during the fermentation process to produce a quality result. This is achieved through the regular use of pH meters – particularly at the beginning of fermentation.
Gone are the days of litmus paper test strips and spending half an hour scrutinizing over which shade of teal it is rendering. Now, digital pH meters are quick, accurate, and affordable tools for you to get the information you need to keep brewing.
But digital pH meters are no silver bullet. It is important they are properly stored so that the probes do not dry out, and are regularly calibrated to get an accurate result.
Here is how you can calibrate your pH meter for brewing and distilling.
(PSA: If you haven’t got a pH meter yet, we have a guide on the best pH meters for brewing and distilling – where we share the exact model we would buy!)
How to Calibrate a pH Meter for Brewing and Distilling
To calibrate your digital pH meter, you’ll need a large container (preferably glass), a bottle of distilled water, and some paper towels.
To perform the calibration, you’ll need a bottle of pH 4, pH 7, and pH 10 buffer solution as well as a cap to cover the end of the probe. It’s a good idea to have some storage solution on hand as well.
Step 1. Clean the probe – Place the probe in a large container and run distilled water over it. Once the probe is completely rinsed, take some of the paper towels and dry the probe. Try to avoid leaving the probe completely dry for too long or allowing it to stand in the distilled water, as it can damage the probe.
Step 2. Put some of the buffer solutions into a small container and lower the probe into it. You can use the 10 pH buffer first. Make sure that the probe is well covered with the solution. Prevent the probe from touching the bottom of the container as it will affect the calibration.
Now press the calibrate button on the pH meter and wait for the reading to stabilize before removing the probe from the buffer.
You can swirl the buffer solution around a bit to make sure that any air bubbles that may have adhered to the probe are knocked off.
After a little while, press the calibrate button again and watch as the reading adjusts to 10 pH. You can then remove the probe from the solution.
Step 3. Place the large container under the probe and wash it thoroughly with distilled water before drying it off with a paper towel.
You need to do this each time you take a reading to avoid the previous sample from contaminating the next one.
Step 4. Repeat the process above for the pH 7 buffer solution. Place the probe in the container and press the calibrate button. You can give the buffer solution a swirl to make sure that the probe is fully in contact with the solution.
Wait for the reading to stabilize and then press the calibrate button again.
The reading will change to the 7 pH of the buffer solution you’ve used.
Step 5. Follow the same procedure as before to obtain a reading for the 4pH buffer solution.
Place a large container under the probe again and wash it off with some more distilled water. Dry the probe with a paper towel and your pH meter is now calibrated and ready for use.
Your pH meter might have a slightly different process depending on the manufacturer. Just check the instruction manual to make sure you follow the guidelines exactly.
You won’t need to calibrate the probe every time you take a reading but bear in mind that the probe will gradually give more inaccurate readings over time. To avoid this problem, calibrate your pH meter each day before taking readings. This will ensure the most accurate measurements each time.
How to Clean Your pH Meter
Remember to wash the probe with distilled water each time, after you’ve taken a reading.
Then gently dry it with a paper towel.
You can leave the probe submerged in pH 4 buffer for up to an hour if you’re not going to use it straight away. But that is not ideal and can damage the probe if left for too long.
Don’t leave the pH meter probe overnight in distilled water or, even worse, dry!
How to Correctly Store Your pH Meter
If you store your pH meter properly, it will greatly extend its useful life.
You should cover the end of the probe with its protective cap containing a small amount of 3 molar potassium chloride.
You can then wash the probe with distilled water the next morning before taking readings again.
What Is a pH Meter and Why Do I Need One?
PH meters are electrical devices that are used to measure hydrogen-ion activity.
This is commonly referred to as the acidity or alkalinity of a solution.
The device is made up of a voltmeter that is connected to a pH-responsive electrode as well as a reference or unvarying electrode. You’ll find that pH-responsive electrodes are normally constructed of glass, which is why they are so easily damaged if you drop them.
Reference electrodes are usually manufactured in silver. You may also come across mercuric chloride or calomel electrodes in more expensive laboratory equipment.
To obtain a reading, the electrodes are submerged in a test solution which then acts as a battery. The electrical charge that develops across the glass electrode correlates with the hydrogen-ion activity in the solution.
This charge is measured in pH units (59.2 millivolts per pH unit at a temperature of 77°F (25°C). The reading you see is the voltmeter reflecting the voltage difference between the two electrodes.
So, what do you do with the reading, once you’ve taken the measurement?
But Why Do I Need a pH Meter?
If you are brewing beer, or in fact, any grain-based alcoholic beverage, knowing what the pH is, plays a critical part in the quality of your final product.
During the mash, pH levels affect the starch conversion as well as the quality of the fermentation. It also plays a role in the flavor and resistance to infection of the batch.
It’s possible to make beer without paying close attention to the pH levels, but your quality will suffer as you won’t have the ability to monitor and control the process in the way that you can if you know what the acidity and alkalinity levels are.
By the same token, knowing the pH levels of your wine is critical throughout the process of controlling microbial stability.
The beneficial microorganisms prefer a less acidic environment, while the microorganisms that prefer a lower pH or more alkaline environment will prove to be a problem due to microbial spoilage.
There is also a key relationship between pH and free SO2. The higher the free SO2, the more effective it is in reducing microbial activity.
Knowing what your pH levels are during the course of your brewing or winemaking has positive spinoffs when evaluating your final product.
Bear in mind that you need to consider temperature when assessing the effects of pH. Adjustments must be made depending on how hot or cold the ambient temperature and liquid are. Some digital pH meters come with automatic temperature control (ATC) that makes allowances for different temperatures.
How to Use a pH Meter for Brewing and Distilling
A pH meter is a simple tool that will help you to control fermentation.
Whether you are making wine, beer, cider, or any other alcoholic beverage, you’ll draw a sample of the liquid and then dip the probes of your pH meter into it to obtain a reading.
As temperature plays an important role in determining pH, you should ideally take your pH measurements at or close to room temperature.
While the automatic temperature control function on many modern pH meters helps, as the temperature of your solution changes, so does the pH level.
There’s no magic to the process though. All you need to do is make sure that you give the sample a quick stir before you take a measurement.
How to Adjust the pH of Your Brew
Homebrewers will generally not need to adjust their pH levels unless they are far from the acceptable range.
This range you want to fall within is typically a mash pH of around 5.2–5.6.
So, what do you do if you’re off these figures and want to make adjustments?
A common problem is when your pH is too high and you need to lower it. Brewers who wish to add calcium ions can use calcium sulfate or calcium chloride. A couple of teaspoons (per 5 gallons / 19 liters) of either of these will often solve the problem and lower the pH to an acceptable level.
Another alternative is adding lactic acid, citric acid, or phosphoric acid to lower the mash pH.
Water with a high pH, with high carbonate levels, can be neutralized by diluting it with distilled water or water that has been produced through reverse osmosis.
For those occasions where the mash pH is too low, calcium carbonate or sodium bicarbonate helps increase the acidity.
Managing the Boil pH
The wort from mashing is boiled at around a pH of 5.0 to 5.2. If your mash pH is right, then your boil pH is usually okay, but not always.
You can tell if you’ve hit the right pH if you see large, fluffy pieces of break material at the start of your boil. You’re doing well if the pH is 5.2 when coagulating the break.
If your pH is too high, the beer will be characterized by a more bitter flavor, which you don’t necessarily want.
The wort color changes due to the amino acids and sugars reacting, giving the beer a darker color. This effect is accentuated at a higher pH so lighter beers require the addition of a little calcium or acid to lower the pH and hence reduce the color.
During fermentation, you can expect the pH to drop as the yeast takes in ammonium ions and gives off organic acids. Naturally, the yeast strain you choose will affect just how much the beer’s pH changes.
It is seldom necessary to adjust the final beer pH as the fermentation process will ensure that the acidity increases naturally. You’ll therefore end up with the pH of finished lagers at 4.2 – 4.6 and ales sometimes around 3.8.
Expect the beer to lighten slightly during fermentation due to molecules decolorizing as the pH decreases.
FAQ – Frequently Asked Questions about Calibrating pH Meters
1. What is a buffer solution
A buffer solution is required to calibrate pH meters before they are used. The solutions are usually set at a pH of 10, 7, and 4 so that the pH meter is correctly set up for taking readings.
2. What buffer solutions do I need?
It is usual for a buffer solution of a pH of 4 and 7 to be used in calibrating pH meters, but you may also require a 10 pH buffer solution for certain meters.
3. How often do I need to calibrate my pH meter?
You should calibrate your pH meter once per day before you take your readings. You can leave it longer between calibrations, but the accuracy of your measurements can suffer.
4. How does temperature affect my pH meter?
As the temperature of your solution rises, so the molecules become more excited, and the number of positively charged hydrogen atoms increases. This lowers the pH as it becomes more acidic.
Sources:
https://beersmith.com/blog/2017/09/21/ph-meters-for-beer-brewing-selection-calibration-and-use/
https://www.britannica.com/technology/pH-meter
https://blog.homebrewing.org/calibrating-a-ph-meter-for-brewing/
