Brewed my own somewhat robust Stout today to check its mash pH

[Silver_Is_Money]

My Hanna meter instructions said to never touch or attempt to wipe the sensor bulb as it would damage the coating on it. So I've always soaked the bulb in the cleaning solution and rinsed it with RO water.

Mine explicitly instructs to damp it dry between samplings. I don't rub it. I merely put a tissue up to it.

 

[ScrewyBrewer]

Mine explicitly instructs to damp it dry between samplings. I don't rub it. I merely put a tissue up to it.

Yep at $57 a shot replacing probes gets expensive.

 

[Silver_Is_Money]

The Apera pH60 was $69 when I bought it. I see they are $79 now on Amazon.

 

[dmtaylor]

How does it fare in a stabilty check?

Not possible to run a proper stability check with the cheap $10 models. It has an auto-turnoff feature after 5 minutes, which even touching the light button every minute will not reset to keep it on. Then when the gauge is restarted, even without moving and standing in the same solution it was in prior to turnoff, the reading jumps to a higher number then slowly levels out over 3-4 minutes to where it ended up 5 minutes before. I did run a test today on 6.86 solution. After about 90-100 seconds or so, I felt it was stable enough to take the initial reading of 6.89. The last thing I saw before it turned itself off was 6.87. So it's reasonably steady. I have no idea what it would do beyond the 5 minutes timeout, but if the standard is 6.86 and I'm within 0.03, I'd say that's plenty good enough for me. I'm not going to fart around with pH readings longer than that anyway. If I want a pH reading at the end of the mash or whatever, I'm going to have to take a fresh reading anyway... and be sure to document it within 5 minutes before the thing turns off.

 

[ajdelange]

The purpose of the stability test is to see if a meter holds its cal long enough to be of practical use. If you wish to use it 15 or 20 minutes after you calibrate it then you want to know that it reads close to the correct pH after 15 or 20 minutes. The fact that your meter shuts itself down after 5 minutes does not keep you from doing a stability check. Just calibrate it and read the buffer after 5 minutes, repeat at 10 minutes and so on.

 

[dmtaylor]

The purpose of the stability test is to see if a meter holds its cal long enough to be of practical use. If you wish to use it 15 or 20 minutes after you calibrate it then you want to know that it reads close to the correct pH after 15 or 20 minutes. The fact that your meter shuts itself down after 5 minutes does not keep you from doing a stability check. Just calibrate it and read the buffer after 5 minutes, repeat at 10 minutes and so on.

Okay. In that respect, it holds its calibration for a long time. The last time I used it was about 2 weeks ago. Didn't need to calibrate it today, and it was consistently reading close to the 6.86 standard.

 

[ajdelange]

Interesting. Usually the cheapos are, if they work at all, incredibly unstable. Even a guy using a $1000 laboratory meter with a $400 electrode can't count on his electrode holding cal for 2 weeks (though I've seen it happen).

 

[dmtaylor]

People are free to waste their money in any way they choose.

 

[ajdelange]

As I am sure you are well aware people buy $1000 meters with $400 electrodes because it is cost effective in the end. Were it not the bean counters would never allow it.

 

[dmtaylor]

Of course. At home, my time spent calibrating and fiddling around waiting for a stable reading is all 100% free, rather than $58/hour.

 

[Rev2010]

The Apera pH60 was $69 when I bought it. I see they are $79 now on Amazon.

This is the one I bought. Only got to use it once so far but liked it much better than the Milwaukee I used to have. It's $79 with 10% off so I got it for like $72. Unlike most others though it's a kit that comes with a small amount of buffer and storage solutions so you can use it right away without buying anything else which is cool. I already bought their buffer & storage solution kit.


Rev.

 

[Silver_Is_Money]

Does anybody else notice that when the pH sample is constantly stirred, the pH continues to fall, fall, fall? I believe due to CO2 from the ambient air dissolving into the beer? It is for this reason that I limit stirring as soon as the reading seems reasonably stable.

I do believe this to be the case, as letting the meter sit in the wort for a few minutes and stabilize always results in a higher reading. Perhaps as much as 0.1 points higher. Yet another reason why many people likely report false low mash pH readings.

In other news, I bottled this stout yesterday, and filled 64 x 12 Oz. bottles (falling just short of a 65th). Would have gotten 65, but used some earlier on during bottling for tasting and for getting the FG reading.

OG = 1.062 (after adding 1 Lb. of highly unfermentable lactose sugar)
FG = 1.021 (which includes the 1 Lb. of lactose sugar)
ABV =~5.5%
Yeasts apparent attenuation = ~73.5% for the 50/50 blend of Windsor and S-O4, so adding the S-O4 accomplished my intended goal here. NOTE: Apparent attenuation was computed after deducting the ~SG contribution of the lactose from both the OG and FG.

Tasted quite good at this stage, albeit perhaps a bit thin (perhaps since I miscalculated for the cold weather and thus mashed at 149.5 degrees instead of my intended 156 degrees) but I've learned over the years not to put any trust in any of such pre-carbonation tasting perceptions. All of my beers inevitably seem to taste great to me at this stage in the game. Some stay that way post carbonation, others become only so-so, and others devolve so far as to crash and burn. I've never gotten a handle on why this phenomenon is so.

 

[ajdelange]

Does anybody else notice that when the pH sample is constantly stirred, the pH continues to fall, fall, fall?

Yes, this has been noticed for many years. It even has a name "stirring error". It is caused by the fact that moving liquid past the bulb of a pH meter disturbs the "double layer" of charges on and near the bulb. The electrode should be swished around in the sample (or buffer) sufficiently to ensure that any adhering rinse water is swept away from the vicinities of the bulb and reference electrode and that the sample is homogenous and the reading taken after the electrode has been still for some time.

It has been noted that stirring error increases the slope of the electrode response. Hence pH values effected by it should appear lower if the pH is less than 7 as you have noted, and higher if the pH is greater than 7.

 

[dmtaylor]

It has been noted that stirring error increases the slope of the electrode response. Hence pH values effected by it should appear lower if the pH is less than 7 as you have noted, and higher if the pH is greater than 7.

Interesting. Thanks.

 

[Silver_Is_Money]

Update: It's now ~3 weeks post bottling, and with this being the first batch I ever brewed for which I intentionally did no aeration step prior to (or after) pitching my 50/50 blend of Windsor and S-O4, I can now report that this has led to 100% success. When using dry yeast I will likely never again waste my time aerating. I can also report that when fermented at 63 degrees (+/- 1), Windsor and S-O4 dry yeasts play rather nice together, as a firm yeast cake layer remained tightly glued to the bottom of the bottle and showed no sign of any yeast rousing during the pour. That plus the achieved FG was that of S-O4 and not that of Windsor. I'm also convinced that the small amount of zinc sulfate that I added along with some Fermaid K yeast nutrient contributed to it's nicely rounded smoothness. Despite using a load of deep roasted malts, and on top of that mashing at a rather low pH of between 5.13 and 5.22, there is (quite to my surprise) no raggedy bitter deep roasted malt edge to it.

Thanks go to Martin Brungard for first bringing the yeasts need for a bit of added zinc for stress reduction and thereby a more rounded smoothness when mashing with RO or distilled water (neither of which contain zinc) to my attention.

 

[ScrewyBrewer]

I followed Martin's water properties advice for a Dry Irish Stout and it came out really good too. I used straight Windsor and the attenuation was a lot lower than WLP-004. It made a very tasty and crushable ~4% ABV beer though.