pH Meter Operation

I was recently asked what my recommendations for pH meter operation were. I’ve compiled my recommendations below. Enjoy!

Calibrate your meter prior to each brewing session to assure that its reporting correctly. Turn the meter on for several minutes to warm up and stabilize the electronics and probe before calibration and use. After that warm up, perform the calibration.

Any meter that has a 4/10 pH adjustment setting, should start the calibration with the 7 pH solution. Tweak the 7 adjustment setting to read the proper value when immersed in the 7 pH solution. Be aware that the 'proper' value changes based on the ambient temperature of the calibration solution. It might be 7.00 or some slightly different pH depending on the calibration solution temperature.

Always rinse the probe with RO or distilled water and then blow off or dab-off all the water droplets from the probe and bulb before moving from one solution (or wort) to another. Always pour out a cap full of calibration solution from the bottle before testing and don't insert the probe into the bottle of calibration solution since that can contaminate the solution. Discard each cap full of solution after you've finished the entire calibration.

Once the 7 setting has been confirmed, move to the 4 pH solution and tweak that setting to read the 'proper' value based on temperature. Rinse the probe and double check the calibration with the 7 solution. Tweak that 7 setting, if necessary. If you had to tweak the 7, you should recheck the 4 reading also.

I recommend using shot glasses made out of glass for holding wort samples. I keep the shot glasses in the freezer since the extra heat capacity of the chilled glass helps cool the hot wort more quickly. Another option is to use a thin glass container and put the container in a cold water bath to cool the sample. Since standard pH probes typically have small diameter, they fit in a shot glass easily and you don't have to place much wort in the glass. Less wort means there is less to cool and the wort cools quicker. Add only enough wort to provide enough wort depth to cover the bulb. pH meters with larger diameter probes will have to use a larger glass container.

Since a shot glass does not require a large wort volume to submerge the bulb, I use an infant medicine dropper to grab a wort sample from the tun. I let that hot wort cool for a moment by swirling it in the chilled glass to help get its temperature down before putting the probe in the wort. Getting the wort down to under 80F helps avoid stressing the probe's glass bulb. Exposing the bulb to hot and cold extremes does increase the chance that it will crack. Poof, goes the probe!

I find that it takes a few minutes for the wort’s pH reading to stabilize. If the hundreth value is jumping back and forth on the meter, the reading is essentially stabilized. If it’s still rising or falling consistently, wait a moment more. Do try and chill the wort to around 65F and record the pH then since that is generally accepted measurement standard. Record your pH reading and return the wort to the tun. Rinse the glass container and probe with RO or distilled water and dry both. Replace the glass in the freezer to rechill. I use 2 glasses so that I can assure the glasses are chilled and can check pH more frequently during the mash.

Storing the pH probe is an important issue. It either needs to be bathed in storage solution or it needs to be sealed in cap or cover with a couple drops of distilled or RO water to keep the glass bulb moist. If you are storing in a cap or cover and using the distilled or RO water, you don't want to add more than a drop or two since you don't want that water to touch the bulb since that can leach some of the electrolyte out of the probe. Electrolyte loss can eventually destroy a probe.