Mash pH was 5.9. Is that realistic?

[kombat]

Motivated by the posts emphasizing mash pH and water quality, I've begun taking my water a little more seriously. Last year, I bought a pH meter, (this one) but never really used it. I tried it a couple of times with plain tap water, and I was getting weird readings (pretty sure my tap water's pH isn't actually 10.0).

So I recently bought a couple of bottles of the buffer test/calibration solution (the 7.0 and the 4.01). I used the 7.0 one and calibrated my meter.

I checked my mash this weekend (brewed an American Lager Saturday morning), and the meter read 5.9. Later, after the brew was finished and I was checking my gravity sample, I measured the wort pH from the sample, and it was still 5.9.

Is this possibly correct? Is it within the expected range? Is my meter screwy/cheap/worthless? Should I be adjusting my mash? Did I waste $100?

 

[mabrungard]

Wort pH is dependent upon the alkalinity of the water used and the acidity of the grains mashed. A pH of 5.9 is entirely possible if you weren't taking measures to move pH in the right direction. Adding an acid to the typical pale grists is a necessary thing.

By the way, why didn't you use the 4.0 solution also? You typically use both solutions to calibrate a meter.

 

[kombat]

Impatient, I guess, and I figured once I'd calibrated it at 7, it should be fine. I'll probably do it again and include the 4.01 solution in the calibration.

 

[didinho]

i never checked ph at the end of the boil, but 5.9 during mash is normal: grains acidify water, and in some cases you don't even need to correct it: for example in stout dark grains give me a ph around 5.7 (with Milan tap water and my mash/grain ratio)

P.S. I use ph card/stick: cheap but well working on 23 liter batches

 

[mattdee1]

I'm also in Ontario but several hours away, so not sure how much our water supplies have in common. I will say this: a pH of high-5's, low-6's is what I would expect in a pale-grain mash using untreated tap water at my house, based on experience. You may notice some grainy/husky flavors in that beer; that was happening to me on pale beers, so I switched to using RO water and building the profile myself.

Regarding your meter calibration, you definitely want to use both the 4 and 7. Keep in mind, the meter doesn't measure pH, it measures a voltage and multiplies that by a calibration factor to report a pH. Doing a single point calibration at 7 will set you up to measure accurately when you're right around 7, but any measurement device requires more than one calibration point to "linearize" or "determine the slope of the curve" -- which are fancy ways of saying "determining the relationship between a change in measured voltage and a change in pH".

 

[kombat]

Alright, so I calibrated it last night with both the 7 and the 4.01 solutions, and I'm still getting weird readings.

When I tested the 7.0 solution, the meter read 7.2. So I hit the "Calibrate" button, and it blinked and read 7.0. I then moved on and did the same thing with the 4.01 solution, but the meter read 4.3. I hit "Calibrate" again, and it said 4.0. I rinsed the probe with distilled water between readings. After all this calibration, I then tried it again in some plain distilled water, and I forget what it read (I know), but I was expecting it to read bang-on 7.0 (isn't distilled water 7.0?), and I believe it was reading considerably lower than that, like 5.9.

Still not sure if I've got a dud on my hands, or I just need to dial it in somehow.

 

[beskone]

Alright, so I calibrated it last night with both the 7 and the 4.01 solutions, and I'm still getting weird readings.

When I tested the 7.0 solution, the meter read 7.2. So I hit the "Calibrate" button, and it blinked and read 7.0. I then moved on and did the same thing with the 4.01 solution, but the meter read 4.3. I hit "Calibrate" again, and it said 4.0. I rinsed the probe with distilled water between readings. After all this calibration, I then tried it again in some plain distilled water, and I forget what it read (I know), but I was expecting it to read bang-on 7.0 (isn't distilled water 7.0?), and I believe it was reading considerably lower than that, like 5.9.

Still not sure if I've got a dud on my hands, or I just need to dial it in somehow.

Sounds right to me, distilled water that's been sitting out can easily have a ph of ~6. Pure non ionized water is exactly 7, but once you expose it to air it starts to absorb co2 from the air lowering the ph. Your meter is probably spot on after the calibration.

Make sure to calibrate every brewday!

 

[ajdelange]

A true mash pH reading of 5.9 is possible but unlikely. If your water has a pH that high or higher and high alkalinity it could happen though.

More important than that is that you apparently made that reading with an uncalibrated meter. Such readings are not to be trusted. And you must, for accurate pH readings in the mash pH region, do a two point calibration (4 and 7 buffer - fortuitously mash pH is just about half way between those two and that is where pH readings are most accurate).

That's still not quite the whole story. Cheap meters (and at $50 that's a cheap meter) are often unstable which means that 5 minutes after you calibrate them they are off. You need to check that your meter is stable before trusting its readings. You do this by checking the pH in the only thing you really know the pH of: the buffers you used for calibrating. The procedure for this stability check is spelled out at:
https://www.homebrewtalk.com/showthread.php?t=302256
which also contains tips on calibration and use, explains what ATC is and so on.

You can't depend on the pH of DI water as reliable as it is not pure water but rather water that has been acidified by dissolving CO2 from the air. DI water, even with dissolved CO2, is very low in conductivity and that makes pH measurement tricky without the use of ion strength adjusters and special buffers. If you could get pure water and measure its pH it would be 7.08 at room temperature (7.00 at 24.7 °C).

 

[kombat]

OK so I calibrated my meter the other night, and tried it again this morning. I took a sample of the early runnings from the mash tun as I was draining to the kettle, and let it cool to room temperature. I tested it with my (now calibrated) meter, and it read 5.5. I think it might actually be working?

 

[FVillatoro]

OK so I calibrated my meter the other night, and tried it again this morning. I took a sample of the early runnings from the mash tun as I was draining to the kettle, and let it cool to room temperature. I tested it with my (now calibrated) meter, and it read 5.5. I think it might actually be working?

The PH of distilled water (from what i've tested) can vary from 7 as low as 5.5 depending on how long it's sat outside.

I always calibrate my meter the same day while I am mashing with PH solutions 7, and then 4.

Make sure that you record the temperature at which the PH calibration solutions are, and then once you drain your wort bring it down to match that temperature (this will help ensure that you are getting the most accurate reading).

I record my readings with pictures as I tend to forget to write things down (testing wort PH on this pic). This PH meter was okay, but my newest Anaheim Scientific one is worlds better.