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Home Brew Forums > Home Brewing Beer > Brew Science > Need reassurance that my problem was likely my pH meter probe!
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Old 08-06-2012, 01:39 PM   #1
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Default Need reassurance that my problem was likely my pH meter probe!

So, I brewed a pale beer yesterday. It had 9lbs pils, .5lbs Caramel Pilsner (9L crystal), .25lbs special roast (50L), and .25lbs acidulated malt. So, that's 2.5% acid malt. I calibrated my meter and checked the pH at about 15 minutes in to the mash. Somehow I got a reading of 5! My water was basically RO (Poland springs with 3 grams of calcium chloride in a thin mash (roughly 2 quarts/lb)). As a little background, I haven't used the meter for ~4-5 months. The probe has been sitting with storage fluid around the glass part of the probe for that time (at least it still seemed to be submerged...didn't look very closely). When I calibrated it the readings were way off initially (4 seemed to be around 4.5...7 maybe around 7.3). Would a cleaning with cleaning solution help? Are my buffers perhaps too old (they're near the end of the bottle and about a year old)? I heard bacteria can change the buffers' pH. I'm not especially worried that my mash was actually at 5, since I tasted the wort and it tasted quite good. Plus, from what I've read on here it's not likely that my mash could actually go that low (unless I accidentally added the wrong amount of acidulated malt, which I don't believe I did.). Anyways, what say you HBT?

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Old 08-06-2012, 02:24 PM   #2
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I find that with RO water, acid or acid malt is only needed with the lightest colored grists. The grist above may have had enough acidity without the inclusion of the acid malt. The low pH may be factual. Did you evaluate the mash pH of that grist with Bru'n Water?

From my experience, old buffers that are kept tightly capped only vary by about a tenth of a unit at that age. That's not good enough to calibrate with, but not so bad as to totally screw up your readings. New buffers are probably a good idea.

I find that dipping the probe in a strong lye solution and a strong acid can help keep probes clean. If I'm not mistaken, the lye destroys cell walls and the acid solubilizes the remains.

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Old 08-06-2012, 02:28 PM   #3
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Originally Posted by mabrungard View Post
I find that with RO water, acid or acid malt is only needed with the lightest colored grists. The grist above may have had enough acidity without the inclusion of the acid malt. The low pH may be factual. Did you evaluate the mash pH of that grist with Bru'n Water?

From my experience, old buffers that are kept tightly capped only vary by about a tenth of a unit at that age. That's not good enough to calibrate with, but not so bad as to totally screw up your readings. New buffers are probably a good idea.

I find that dipping the probe in a strong lye solution and a strong acid can help keep probes clean. If I'm not mistaken, the lye destroys cell walls and the acid solubilizes the remains.
Yes, both Bru'n Water and Ez Water estimated 5.4 (EZ Water was actually 5.44). I'll certainly get new buffers the next time I use my meter, though. I'll also try the cleaning solution I have for my probe.
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Old 08-06-2012, 02:46 PM   #4
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You were probably OK and your probable pH would have been about 5.50 but of course I'm guessing. Obviously you want to check out your pH meter. The first thing to do is get fresh buffers and try to calibrate your meter with them. Follow your manufacturer's instructions but as they are sometimes sketchy you might want to have a look at the sticky on pH meter calibration here. Be sure to do the stability check after calibration. In this test you keep checking the pH of one of the buffers over time. It obviously should read the same thing every time but if the meter has slowed response and the calibration algorithm doesn't take this into account you can get a miscalibration and drifting response.

The biggest problem with buffers is that they get contaminated either with sample, the other buffer in the pair or the DI water used to rinse the electrode between buffers/samples. Yes, bacteria can grow in them and this can pull the pH. As a consequence of this the buffers contain antibacterial components. But don't trust a liquid buffer (or powders either for that matter) that are past their expiration dates. Never return used buffer to the stock bottle. Do all calibration and measure all samples at as close to the same temperature as you can (whether the meter has ATC or not).

Meter electrodes do age and they do get dirty. How old is this meter? Aging usually manifests itself by slowed response, reduced slope and increasing offset or any one or any combination of these. If your meter reports slope and offset to you take note of these. Slope should be at least say 52 mV/pH and offset less than say ± 10 mV. In brewing the biggest problem is fouling of the reference junction with protein. This is easily removed with an enzyme based cleaner such as Zymit. Avoid harsh chemicals if you can. Lye, for example, dissolves glass. In days of yore that was a common method of 'rejuvenating' electrodes (though the etching was usually done with hydrofluoric acid). I haven't seen anything harsher than enzyme based cleaners recommended in a long time. But then rejuvenation isn't so likely to be necessary these days. I've had electrodes last 3 yrs and have heard reports of even longer life than that.

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Old 08-06-2012, 03:02 PM   #5
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You were probably OK and your probable pH would have been about 5.50 but of course I'm guessing. Obviously you want to check out your pH meter. The first thing to do is get fresh buffers and try to calibrate your meter with them. Follow your manufacturer's instructions but as they are sometimes sketchy you might want to have a look at the sticky on pH meter calibration here. Be sure to do the stability check after calibration. In this test you keep checking the pH of one of the buffers over time. It obviously should read the same thing every time but if the meter has slowed response and the calibration algorithm doesn't take this into account you can get a miscalibration and drifting response.

The biggest problem with buffers is that they get contaminated either with sample, the other buffer in the pair or the DI water used to rinse the electrode between buffers/samples. Yes, bacteria can grow in them and this can pull the pH. As a consequence of this the buffers contain antibacterial components. But don't trust a liquid buffer (or powders either for that matter) that are past their expiration dates. Never return used buffer to the stock bottle. Do all calibration and measure all samples at as close to the same temperature as you can (whether the meter has ATC or not).

Meter electrodes do age and they do get dirty. How old is this meter? Aging usually manifests itself by slowed response, reduced slope and increasing offset or any one or any combination of these. If your meter reports slope and offset to you take note of these. Slope should be at least say 52 mV/pH and offset less than say ± 10 mV. In brewing the biggest problem is fouling of the reference junction with protein. This is easily removed with an enzyme based cleaner such as Zymit. Avoid harsh chemicals if you can. Lye, for example, dissolves glass. In days of yore that was a common method of 'rejuvenating' electrodes (though the etching was usually done with hydrofluoric acid). I haven't seen anything harsher than enzyme based cleaners recommended in a long time. But then rejuvenation isn't so likely to be necessary these days. I've had electrodes last 3 yrs and have heard reports of even longer life than that.
Wow, thanks for the long response! The electrode is about 8 months old maybe, if I had to guess? It hasn't seen a ton of use though, especially in the past 5 months. I suppose I'll get some fresh buffers the next time I use them. Ultimately I suppose I shouldn't be too worried. The sample tasted good, and I was getting a lot of coagulation of proteins post boil in my hydrometer jar, so I'm guessing I probably wasn't as low as 5, but we'll see how the final result tastes. The OG was ~1.055 and I used nottingham, which is a pretty quick yeast, so hopefully In 3-4 days I'll be able to take a green sample to get an idea of the results.
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Old 08-06-2012, 06:15 PM   #6
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I've noticed that Castle pilsner has resulted in about 0.2 pH (room temp) lower mash pH's than if I had used Weyermann pilsner - will be mashing Castle again this week and have another data point to verify that claim. Either way your mash is probably at least 5.3 at room temp instead of the 5 you measured.

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Old 08-06-2012, 06:36 PM   #7
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I've noticed that Castle pilsner has resulted in about 0.2 pH (room temp) lower mash pH's than if I had used Weyermann pilsner - will be mashing Castle again this week and have another data point to verify that claim. Either way your mash is probably at least 5.3 at room temp instead of the 5 you measured.
I was using Weyermann, so I'm probably OK. The reading was just bugging me, hence the thread. How do you like Castle? I tend to brew Belgian-style beers most often, so I may get a sack of Castle pils next.
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Old 08-06-2012, 07:00 PM   #8
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I was using Weyermann, so I'm probably OK. The reading was just bugging me, hence the thread. How do you like Castle? I tend to brew Belgian-style beers most often, so I may get a sack of Castle pils next.
I've liked everything made with Weyermann malts, can't really comment yet on Castle. I've just gotten into brewing Belgians this Spring & blindly using Castle malts wherever possible for those just because it's from Belgium. Switching base malts goes against some of the advice I've heard from Jamil about maintaining a consistent continental pilsner and really getting to know it.
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Old 08-06-2012, 07:05 PM   #9
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I've liked everything made with Weyermann malts, can't really comment yet on Castle. I've just gotten into brewing Belgians this Spring & blindly using Castle malts wherever possible for those just because it's from Belgium. Switching base malts goes against some of the advice I've heard from Jamil about maintaining a consistent continental pilsner and really getting to know it.
Have you noticed much of a flavor difference, Weyermann vs Castle? I suppose it'd be hard to notice unless you did something like a pilsner with both (or perhaps a pilsner and a blonde)
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Old 08-06-2012, 07:37 PM   #10
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Have you noticed much of a flavor difference, Weyermann vs Castle? I suppose it'd be hard to notice unless you did something like a pilsner with both (or perhaps a pilsner and a blonde)
I think you'd have to do an experiment like you suggested and control every other variable.

Other than bottling, I haven't opened a Belgian that I brewed yet this Spring/Summer in an attempt to build a backlog of high gravity aged beers between quicker turnaround ales.
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