Measuring Ph of mash and temp corrected readings

[frettfreak]

Until recently I thought I had a pretty good handle on my mash pH and chemistry but I just read something that made me question myself.

In the May / June 2017 issue if Zymurgy, there is an article about mash pH. There wasn't anything new to me until I read this:

"Once the sample has cooled to room temperature, take the reading. The pH of the sample at room temperature will be about .3 higher than the pH at mash temperature. Thus if you get a reading of 5.6 for your cooled sample, the corrected reading is roughly 5.3."

Obviously I know there are different readings at different temps and that you should be cooling your sample before taking a reading (even if you have an auto temp correcting meter). I do that every time. Where my confusion is in the corrected readings.

Depending on the beer, I will be anywhere from 5.2 - 5.5 and usually hit my target (I use Bru'n water). But that's the reading on my cooled sample. So according to the article, if the pH of my cooled sample 5.2, my actual mash pH is 4.9!?!? :smack:

I feel like an idiot if this is the case!!! Can someone with some knowledge chime in here and tell me if i have been doing this all wrong?!?!?

Thanks in advance!

 

[mabrungard]

The pH at wort temperature is not relevant. Target and measure room-temperature pH only! Build your experience of what pH works for your beers by calibrating your experience to ROOM-TEMPERATURE measurements.

 

[ajdelange]

Thus if you get a reading of 5.6 for your cooled sample, the corrected reading is roughly 5.3."

This is not right. The corrected reading is 5.6 at laboratory temperature and all references to pH readings are at laboratory temperature. Except when they aren't. Few authors explicitly state that pH readings are at laboratory temperature (with DeClerck being a notable exception) and some, though it is rare these days (Gordon Strong) refer all pH readings to mash temperature. Usually you can tell which the author has in mind as it is pretty well accepted that proper mash pH is between 5.4 and 5.6 at room temperature. If you see people talking about mash pH in or close to that band you can be pretty sure room temperature is being discussed. If you see a range of 5.2 to 5.4 then it's probable that mash temperature is being discussed.

There are, of course, advantages to doing it both ways with the major advantages of room temperature being that it is easy on electrodes and room temperature is always 20 °C whereas mash temperature might refer to a protein rest temperature, a low saccharification rest or a high saccharification rest. One can work on the assumption that all malts have the same 'glide' (what I call the derivative of pH with temp) and use that to justify room temperature but a little experimentation with a few malts quickly taught me that they don't all have the same glide at all. Thus using room temperature to predict and measure pH introduces error as the actual reactions of interest take place at mash temperature IOW that is what is actually relevant. The approximations we obtain by using the standard practice (room temperature) are generally close enough.

This uncertainty is just something we have to live with. Responsible authors always state the temperature and the pH!

 

[Silver_Is_Money]

This issue seems to repeat itself periodically, and is often fueled by brewing magazine articles.

The actual pH is the 25 degrees C. (77 degrees F.) pH, as that is the only temperature at which a pH 4 buffer and a pH 7 buffer will actually read pH 4 or pH 7 respectively (by design).

If you get your sample to the ideal 25 degrees C. you will not need temperature compensation. If your pH meter has ATC (automatic temperature compensation) it will purportedly give correct readings within a few degrees C. of the ideal 25 degrees, as well as internally compensate for the inherent non-ideal pH slope of a "real world" electrode vs. the theoretical ideal electrode output, and therefore still read decently correctly at what most would accept as a nominal "room temperature". Your pH meter should ideally be calibrated at 25 degrees C. also, but for all practical purposes calibration and sampling at 20 degrees C. is accurate enough for mashing.

I do not have the magazine to verify what it is actually attempting to state, but if you take a pH reading at a typical mash temperature and it is 5.3, your actual and proper 25 degree C. mash temperature pH will be roughly 5.6 (give or take). If you have expressed it as stated in the article, then its author is in error.

https://mashmadeeasy.yolasite.com/

 

[ajdelange]

If you get your sample to the ideal 25 degrees C. you will not need temperature compensation. If your pH meter has ATC (automatic temperature compensation) it will purportedly give correct readings within a few degrees C. of the ideal 25 degrees, as well as internally compensate for the inherent non-ideal pH slope of a "real world" electrode vs. the theoretical ideal electrode output, and therefore still read decently correctly at what most would accept as a nominal "room temperature".

This isn't quite correct. https://www.homebrewtalk.com/showthread.php?t=198460

See Your pH meter should ideally be calibrated at 25 degrees C. also, but for all practical purposes calibration and sampling at 20 degrees C. is accurate enough for mashing.

As the referenced post explains (and then in subsequent posts goes into more detail) a meter can be calibrated at any temperature as the pH's of the buffers at all reasonable temperatures are stored in the meter. It also explains that a meter calibrated at T1 can very well measure the pH of a sample at T2 provided that the isoelectric pH (pHi) of the electrode is exactly 7 or that the actual pHi of the electrode can be entered into the calibration algorithm. Under these circumstances the two calibration buffers don't even need to be at the same temperature!

A full calibration measures slope, offset and pHi. The more usual calibration assumes pHi = 7 and estimates the slope and offset of the meter. ATC adjusts gain for the temperature of the electrode at the time of the measurement relative to the slope at some reference temperature.

I have never seen a pH meter that allows the user to enter pHi but I have seen electrodes with pHi greater than 8 (the usual goal is 6 < pHi < 8) and this is because the algorithms are not very sensitive to pHi.

So calibrate your meter with buffers near room temperature and make your sample measurement near room temperature with confidence that your calibration and temperature correction (for the electrode slope only!) will be correct but for fine work have buffers and samples at as close to the same temperature as possible. This does not 'stress' ATC.

 

[frettfreak]

The pH at wort temperature is not relevant. Target and measure room-temperature pH only! Build your experience of what pH works for your beers by calibrating your experience to ROOM-TEMPERATURE measurements.

So what I have been doing is correct. Making sure my temp adjusted readings are within the "ideal" range?

This is not right. The corrected reading is 5.6 at laboratory temperature and all references to pH readings are at laboratory temperature. Except when they aren't. Few authors explicitly state that pH readings are at laboratory temperature (with DeClerck being a notable exception) and some, though it is rare these days (Gordon Strong) refer all pH readings to mash temperature. Usually you can tell which the author has in mind as it is pretty well accepted that proper mash pH is between 5.4 and 5.6 at room temperature. If you see people talking about mash pH in or close to that band you can be pretty sure room temperature is being discussed. If you see a range of 5.2 to 5.4 then it's probable that mash temperature is being discussed.

There are, of course, advantages to doing it both ways with the major advantages of room temperature being that it is easy on electrodes and room temperature is always 20 °C whereas mash temperature might refer to a protein rest temperature, a low saccharification rest or a high saccharification rest. One can work on the assumption that all malts have the same 'glide' (what I call the derivative of pH with temp) and use that to justify room temperature but a little experimentation with a few malts quickly taught me that they don't all have the same glide at all. Thus using room temperature to predict and measure pH introduces error as the actual reactions of interest take place at mash temperature IOW that is what is actually relevant. The approximations we obtain by using the standard practice (room temperature) are generally close enough.

This uncertainty is just something we have to live with. Responsible authors always state the temperature and the pH!

So what would be your advice based on your experience? Continue to measure at room temp and aim for a higher pH in the "ideal" range? 5.4-5.5 at room temp?? Sorry, just not quite sure what your recommendation was.

 

[mabrungard]

So what would be your advice based on your experience? Continue to measure at room temp and aim for a higher pH in the "ideal" range? 5.4-5.5 at room temp?? Sorry, just not quite sure what your recommendation was.

I'm a little surprised by that recommendation. My experience has shown me that a more appropriate room-temperature mashing pH should always be in the 5.2 to 5.6 range and can be further refined with respect to the style brewed and the brewer's preferences.

 

[Qhrumphf]

I don't think there's unanimous agreement on the "ideal" range. With a few exceptions (highly roasted beers) I don't like room temp pH of 5.6. I tend to prefer 5.3-5.5 room temp (most targeting 5.4-5.45). In some cases I'll aim as high as 5.55 or as low as 5.25, but those are only in specific cases.

I hadn't considered there actually being a legitimate reason to read at mash temp, the wear and tear on the electrode has always been enough to convince me to read at room temp (at least after quickly destroying my first one from always reading at mash temp).

 

[Gadjobrinus]

Aren't we talking, for the most part, of pH meters that get nowhere close to these accuracy measurements (I've always used the Extech pH 110 - to good effect for cheese, and beer. Meaning they've turned out well. Most likely, my obsessive interventions regardless of pH along the way)? A bench meter, sure....but in practice, aren't these meters "one brewer's 5.3 is another's 5.5?"

Not urging a conclusion, I'd really like to know. If one can truly count on a truly countable accuracy out to .1, corroborating the company's lit, I'd personally be very pleased.

 

[Silver_Is_Money]

In truth, so many educated guesses are being made by any mash pH prediction software that shooting for the nominal ideal midrange mash pH value of 5.4 with them is generally a safe bet.

Any such software package does not know the actual DI Mash pH's for any specific malt in a grist bill (unless the brewer has tested his individual malts, and the software allows for manual override whereby the actual values can be input), and therefore the software must use math model algorithms designed to guess the DI mash pH for each grist bill component. The hope being that, in a sort of fuzzy logic kind of way, some malts in the grist bill will be guessed pH high, and some pH low, with the average error cancelling out and consequently mirroring the overall reality of the actual grist bill components (the recipe) as a whole.

And just as importantly the same applies to strike water mineralizations actual impact upon the mash pH. The software does not know the precise buffering capacities so again it math model guesses. It does not know the true impact of your waters mineralization with respect to the Kolbach ideal pH shift, so again it guesses. We know now that Kolbach measured the impact of mineralization upon pH well downstream at knock-out and not during the mash at all, let alone early in the mash, and we also know that knock-out pH is often found to be about 0.2 lower than mash pH, so if software aggressively applies Kolbach's mineralization pH shift equation to the mash it will inherently predict a noticeably lower mash pH than software which actually tries to take this knowledge into consideration.

And lastly the software must assume that the strike water analyticals you input are a close reflection of your actual waters analysis at the very moment wherein you gathered it up for the brew session.

In the end it's a vast multiplicity of educated guesses by software math models iintended to mimic reality, and if all of the modeled guesses average out the software will appear to the end user to know what it is doing, but if all of the guesses fail to average out and mirror your actual grist, minerals impact, and water analyticals the software will be off. Sometimes it appears to win the game, and sometimes it doesn't. But how it plays the game (the overall validity of its algorithms) is also seriously important.

So given all of the merely educated guesswork that is at play, I again must reiterate that using such software to target the mash pH mid-range of 5.4 is never a bad initial bet. It allows for the potential of software error at a magnitude of +/- 0.2 pH, while still keeping you within the ballpark.

And lastly, in all of this do not lose sight of the necessity to measure mash pH at or very near room temperature. None of the above considers the inherent potential for error from the pH meter and the methods of the end user in calibrating and utilizing it, which adds still more potential for error (with this error not being the fault of mash pH prediction software).

https://mashmadeeasy.yolasite.com/

 

[Qhrumphf]

The first time with a given recipe, sure, you're ballparking it no matter what you do. Although over the years I've found Bru'N Water to be remarkably accurate to measured pH- usually within 0.05, especially if using 88% lactic acid. Acid malt is more variable.

Dialing in comes from brewing the same recipe over and over and knowing what pH gives you the outcome you want and adjusting accordingly. Some homebrewers do this. Many do not. Again acid malt's variance makes it difficult, using actual lactic acid is more consistent in my experience. Also helps to have the same general grouping of malts to draw from.

 

[ajdelange]

I'm a little surprised by that recommendation.

The quoted post here says the ideal range is 5.4 - 5.5. The range I offered was 5.4 - 5.6.

My experience has shown me that a more appropriate room-temperature mashing pH should always be in the 5.2 to 5.6 range

pH values between 5.4 and 5.6 are always, without exception, between 5.2 and 5.6.

and can be further refined with respect to the style brewed and the brewer's preferences.

Expanding the range is the opposite of refining it but I certainly agree that people may want to make beers with mash pH's that fall outside the 5.4 > pH < 5.6 range on occasion.

pH is ultimately like any other variable such as sulfate content. There may be, for a particular consumer for a particular style (or more likely for a particular grist) a pH which produces the 'best' beer by some unspecified criterion of optimality (IOW there are several candidates) but a brewer isn't going to know what that is going in. It's probably going to fall between 5.4 and 5.6. It's going to fall between 5 and 6 with probability higher still.

 

[Silver_Is_Money]

What must be removed from the reporting of success with any such mash pH software is a form of bias that hinges upon apologetics. The nature of this bias is one whereby the software user virtually worships the software and trusts it so implicitly that when actual measured results deviate from the software, the software is defacto presumed correct and the user discards or dismisses their own pH readings as being in error and thereby untrustworthy of living up to the standards of the worshiped software. The result being that these readings are not recorded and certainly not publicly reported, lest one expose their own weakness in not being true to the exalted software to the entire world. As a consequence, others watching from the outside see only an endless stream of published success stories, and they then begin to also exalt the software to a plateau of near godly status. And so on, and so on....

I'm aware of a vast number of software users who have seen the success stories of others, and not having seen or been made aware of their failures, they thereby do not even consider or attempt to measure mash pH, simply because the software has ascended to a plateau of exaltation within their mind to where they feel it completely unnecessary to actually and carefully measure mash pH. And when the beer tastes good, the reports go out praising the software, but again, when the beer tastes bad, such reporting does not often happen (and even when it does, it does not generally even suspect or ever mention that the software may have been part of the problem). This bias merely perpetuates the software myth cycle.

Software is clearly better than merely guessing, but to state or presume implicitly that any such software is going to be nigh on dead on correct for most all cases in clear violation of the application of reasonable +/- error bars (statistical probability bars) is a serious stretch. And in such cases an apologetics/bias must be weighed and considered.

https://mashmadeeasy.yolasite.com/

 

[ajdelange]

So what I have been doing is correct. Making sure my temp adjusted readings are within the "ideal" range?

Yes.

So what would be your advice based on your experience? Continue to measure at room temp and aim for a higher pH in the "ideal" range? 5.4-5.5 at room temp?? Sorry, just not quite sure what your recommendation was.

Continue to do what you have been doing i.e. measure at room temperature and adjust the value at room temperature under the supposition that you will find a pH at room temperature that gives the best result whatever actually happens at mash temperature.

I often use the analogue of what pilots do when flying higher than 18,000 ft (FL180). They all set their altimeters to 29.92. The pressure, wherever they are, is unlikely to be 29.92 but as everyone is set for the same a guy whose altimeter says he is at FL180 is not at the same altitude as a guy whose altimeter says he's at FL181 and they don't collide. The 29.92 reading doesn't reflect the correct altitude (that's why they call it the flight level) but it provides useful information about the actual altitude. Similarly the room temperature mash pH isn't the mash pH but it provides useful information about it

 

[ajdelange]

Aren't we talking, for the most part, of pH meters that get nowhere close to these accuracy measurements (I've always used the Extech pH 110 - to good effect for cheese, and beer. Meaning they've turned out well. Most likely, my obsessive interventions regardless of pH along the way)? A bench meter, sure....but in practice, aren't these meters "one brewer's 5.3 is another's 5.5?"

There is lots of debate on this but no, most of us use a decent meter capable of 0.02 accuracy and while many swear by the Chinese junk meters (and get quite hot under the collar when there shortcomings are pointed out) most realize that they are not really suited for brewing.

Not urging a conclusion, I'd really like to know. If one can truly count on a truly countable accuracy out to .1, corroborating the company's lit, I'd personally be very pleased.

Do you really understand the implications of accuracy of 0.1? Most people don't without at least stopping to think about it. I tried to illustrate what it really means in a recent post at https://www.homebrewtalk.com/showthread.php?t=589832&page=8 Have a look at No. 72 there.

 

[ajdelange]

What must be removed from the reporting of success with any such mash pH software is a form of bias that hinges upon apologetics.,,,

It has a name. Confirmation Bias. It is the investigators constant companion and worst enemy. I don't know exactly how it works with brewing calculators but I have my suspicions and those are that the brewer runs the calculator, gets a predicted mash pH, inserts his meter and watches the numbers roll by. As mash pH readings vary quite a bit over a half hour or more eventually the meter reads (this won't always happen, of course) pretty close to what the program predicted and the brewer takes note of that saying to himself 'Man, that SudsoBrew. Spot on again!'. An important aspect of confirmation bias is that one remembers that which confirms his biases and forgets those things which contradict. Thus when the program is way off in left field he says to himself 'SudsoBrew is always right on so I must have entered the data wrong', resolves to check on it later but somehow never gets around to it and very probably does not remember this episode when discussing the relative merits of SudsoBrew and Brewer's Mentor with his buddies.

We know Confirmation Bias is at play because it is always there, many people are unaware that such a thing even exists (and so do not take steps to combat it) and because some claims are made for programs that are just impossible given the physics of the problem (e.g. programs reported to be more accurate than the level to which one can measure pH with a good meter.

 

[Gadjobrinus]

In truth, so many educated guesses are being made by any mash pH prediction software that shooting for the nominal ideal midrange mash pH value of 5.4 with them is generally a safe bet.

Any such software package does not know the actual DI Mash pH's for any specific malt in a grist bill (unless the brewer has tested his individual malts, and the software allows for manual override whereby the actual values can be input), and therefore the software must use math model algorithms designed to guess the DI mash pH for each grist bill component. The hope being that, in a sort of fuzzy logic kind of way, some malts in the grist bill will be guessed pH high, and some pH low, with the average error cancelling out and consequently mirroring the overall reality of the actual grist bill components (the recipe) as a whole.

And just as importantly the same applies to strike water mineralizations actual impact upon the mash pH. The software does not know the precise buffering capacities so again it math model guesses. It does not know the true impact of your waters mineralization with respect to the Kolbach ideal pH shift, so again it guesses. We know now that Kolbach measured the impact of mineralization upon pH well downstream at knock-out and not during the mash at all, let alone early in the mash, and we also know that knock-out pH is often found to be about 0.2 lower than mash pH, so if software aggressively applies Kolbach's mineralization pH shift equation to the mash it will inherently predict a noticeably lower mash pH than software which actually tries to take this knowledge into consideration.

And lastly the software must assume that the strike water analyticals you input are a close reflection of your actual waters analysis at the very moment wherein you gathered it up for the brew session.

In the end it's a vast multiplicity of educated guesses by software math models iintended to mimic reality, and if all of the modeled guesses average out the software will appear to the end user to know what it is doing, but if all of the guesses fail to average out and mirror your actual grist, minerals impact, and water analyticals the software will be off. Sometimes it appears to win the game, and sometimes it doesn't. But how it plays the game (the overall validity of its algorithms) is also seriously important.

So given all of the merely educated guesswork that is at play, I again must reiterate that using such software to target the mash pH mid-range of 5.4 is never a bad initial bet. It allows for the potential of software error at a magnitude of +/- 0.2 pH, while still keeping you within the ballpark.

And lastly, in all of this do not lose sight of the necessity to measure mash pH at or very near room temperature. None of the above considers the inherent potential for error from the pH meter and the methods of the end user in calibrating and utilizing it, which adds still more potential for error (with this error not being the fault of mash pH prediction software).

https://mashmadeeasy.yolasite.com/

Beyond my ken and an education in a post. Another line to start digging, in coming back. Thanks, Silver. Great post.

 

[Gadjobrinus]

There is lots of debate on this but no, most of us use a decent meter capable of 0.02 accuracy and while many swear by the Chinese junk meters (and get quite hot under the collar when there shortcomings are pointed out) most realize that they are not really suited for brewing.



Do you really understand the implications of accuracy of 0.1? Most people don't without at least stopping to think about it. I tried to illustrate what it really means in a recent post at https://www.homebrewtalk.com/showthread.php?t=589832&page=8 Have a look at No. 72 there.

OK, as usual, left me with questions and the need to re-read. Are you aware of the implications of requiring a brain with bad wiring to re-read something so insightfully fascinating, that the user's head is likely to explode by round II?

Nope, kidding. It is sincerely fascinating. I've been fluent in French since I was a young snot and have an ease in learning languages, though much of that has ebbed away now; I was a political economic historian at Berkeley; all science and math has come the hard way, though I love it.

Meaning to say, I'll have to sit and consider and work through all the stuff you guys go through. Just want to thank you for going through it, for "our" benefit.

A more prosaic question. I don't recall what I used those 15-20 years ago when I last brewed, but I was very proud to hit numbers routinely. OGs and pH samplings were generally on.

Shoot to 4-5 years ago now, and cheesemaking. Using the Extech was a bit of an exercise in frustration. The first meter was just a bad meter and they sent another one. Then again. On the 3rd try, we seemed to hit a workable meter. The fact they so easily sent replacements (I didn't have to send the others back) told me, this wouldn't be the first time. They have to be in such a margins game, to be able to do this.

At any rate, my confidence wasn't great. Generally, more "trustworthy" when measuring slurries of one kind or another, say, just after curing and cutting up the curd, or after the cook, before first pressings. Not so good when trying to measure the wheel itself.

At any rate, Extech. My genius friend (I won't reveal his name. He's a California goat farmer and cheesemaker, who also does computer security stuff for nations and the like....there is nothing this guy doesn't know, in my experience) has a bench model I dreamed of, but we haven't been in touch in a few years. And I'm also looking for a portable meter I can take with me outside, for ready testing. Is that possible? Bottom line, foregoing the dedicated bench meter for the dedicated lab one dreams of (OK, see attached), is there a decent meter anyone could recommend for the brewday need?

View attachment Cask Conditioning Brewery - MBS21.pdf

 

[Gadjobrinus]

Yes.



Continue to do what you have been doing i.e. measure at room temperature and adjust the value at room temperature under the supposition that you will find a pH at room temperature that gives the best result whatever actually happens at mash temperature.

I often use the analogue of what pilots do when flying higher than 18,000 ft (FL180). They all set their altimeters to 29.92. The pressure, wherever they are, is unlikely to be 29.92 but as everyone is set for the same a guy whose altimeter says he is at FL180 is not at the same altitude as a guy whose altimeter says he's at FL181 and they don't collide. The 29.92 reading doesn't reflect the correct altitude (that's why they call it the flight level) but it provides useful information about the actual altitude. Similarly the room temperature mash pH isn't the mash pH but it provides useful information about it

Stumped (esp. .bolded). I know you're not saying this, but I'm reading, take a room temp reading, if it says 5.1, simply adjust that to 5.4, as that's a useful value. I know, stupid as I know that's not what you're saying, but short-circuiting is kicking in. Sorry to all.

 

[ajdelange]

I know you're not saying this, but I'm reading, take a room temp reading, if it says 5.1, simply adjust that to 5.4, as that's a useful value.

That is exactly what I am saying.

 

[Gadjobrinus]

That is exactly what I am saying.

I do not mean to be obtuse, but what I literally mean is if the meter says 5.1, I say, basically, "that can't be right! The wort is supposed to be 5.4, to be ideal. So, the meter really means 5.4!"

Or did you mean, adjust the mash with acid, let's say, until your room temp pH meter now indicates 5.4?

Again, obtuseness not intended...

 

[ajdelange]

No problem. I should have read more carefully before I started typing.

If you measure a mash pH of 5.1 when you designed a beer for a mash pH of 5.4 (at room temperature) clearly something is wrong. The first thing to do is to check the pH meter cal by sticking it in pH 4 buffer. Assuming it checks out then you have made and error in the composition of the mash or have added too much acid or your alkalinity is actually a lot less than you think it is. It is probably too late but yes, what I meant to say was that your only recourse at this point would be to add base (absorb acid) to try to get the pH up to 5.4 because in most cases a mash pH of 5.4 (at room temperature) will produce a good beer even though the actual pH of the mash at mash temperature may be 5.2.

 

[Gadjobrinus]

Sorry, boy, I am spacing. I should have said base, to get it up to 5.4.

OK thanks, AJ. Now - you probably address this is the other thread you referenced me to - but what if, though it checks out in the buffer pH 4, you have a crappy meter with crazy drift, or some other flaw such that it was simply misreading a 5.4 room temp as a 5.1 room temp? (E.g., with the Extech, I had to rinse, dry, dual-calibrate after each and every measurement).

Basically, I guess, what gives us confidence, in a meter?

 

[Qhrumphf]

It has a name. Confirmation Bias. It is the investigators constant companion and worst enemy. I don't know exactly how it works with brewing calculators but I have my suspicions and those are that the brewer runs the calculator, gets a predicted mash pH, inserts his meter and watches the numbers roll by. As mash pH readings vary quite a bit over a half hour or more eventually the meter reads (this won't always happen, of course) pretty close to what the program predicted and the brewer takes note of that saying to himself 'Man, that SudsoBrew. Spot on again!'. An important aspect of confirmation bias is that one remembers that which confirms his biases and forgets those things which contradict. Thus when the program is way off in left field he says to himself 'SudsoBrew is always right on so I must have entered the data wrong', resolves to check on it later but somehow never gets around to it and very probably does not remember this episode when discussing the relative merits of SudsoBrew and Brewer's Mentor with his buddies.

We know Confirmation Bias is at play because it is always there, many people are unaware that such a thing even exists (and so do not take steps to combat it) and because some claims are made for programs that are just impossible given the physics of the problem (e.g. programs reported to be more accurate than the level to which one can measure pH with a good meter.

The other factor is the quality of data input. Unless you're accurately testing before brewing, or starting with a purely consistent-ish source (RO or distilled), you don't know for sure what you're dealing with. Many homebrewers and hell a lot of pros pull one water report and just go on that.

I go based on monthly averages, which while not as good as testing every time, gets close enough.

So when measured pH is off from calc, is it the calculator? Is it the data input? Is it variance in grain acidity? Is it some form of user measurement error? I don't know. If I ever question the reading itself (extreme readings- a couple times I've been careless and contaminated the sample with additonal lactic acid and read well into the 4's) I'll always recalibrate the meter and grab a new sample. But it could be any of them. But routinely close enough is close enough. I don't sweat pH too much as long as it's in range and close-ish to target. A stout <5.35 measured I'll add alkalinity. A pale lager >5.45 I'll add more acid, etc. Otherwise I will generally just note for next time and not worry about it.

 

[mabrungard]

pH values between 5.4 and 5.6 are always, without exception, between 5.2 and 5.6.

Expanding the range is the opposite of refining it but I certainly agree that people may want to make beers with mash pH's that fall outside the 5.4 > pH < 5.6 range on occasion.

Thanks for the clarification on the obvious point, but I was disputing your original range. It is fine, but I have found that the desirable range is wider than you stated.

The refinement mentioned in my post was for the brewer to refine THEIR pH target based on their preferences and style brewed.

PS: Does anyone else have a problem with participants authoritatively posting on this forum while remaining comfortably anonymous behind an assumed avatar? You'll notice that AJ and I stand behind our names for what we say on this forum. It certainly keeps us honest.

 

[Gadjobrinus]

I hear you on your p.s., Martin. My authority, which I know to be very grave, very grave indeed, is by the name Paul Smith, out of Madison, WI. Howdy!

 

[Qhrumphf]

PS: Does anyone else have a problem with participants authoritatively posting on this forum while remaining comfortably anonymous behind an assumed avatar? You'll notice that AJ and I stand behind our names for what we say on this forum. It certainly keeps us honest.

I'm not sure if that's directed at anyone on this thread in particular. I certainly don't purport to be a scientist or an authority outside of a few select realms (say, beer judging). Plus at least if you look via website and not mobile app it's not hard to figure out who I am.

However, it's an internet forum. Anonymity and stupidity are part of it. Over time I've learned who is a useful source of information on here and who is not - you and AJ certainly in the former camp. Others who I shan't name put up a facade of knowledge and experience but I've learned they're mostly full of it. Unfortunately newer folks don't have that experience and can be misled (as I certainly was in many ways as a new brewer), but such is life. Having everyone use their real name as a handle isn't gonna do much to prevent any of it.

Although at the end of the day I do opt to take my information from someone who will put their name on the line- you, AJ, Bamforth, Kai, Fix, etc, than some rando on the internet, so I see where you're coming from.

 

[ajdelange]

Thanks for the clarification on the obvious point, but I was disputing your original range. It is fine, but I have found that the desirable range is wider than you stated.

I really don't have a problem with that. Best pH is certainly distributed. My gut says the mean is about 5.45 but I really can't justify that beyond saying that it is my gut. So do we want to say the optimum range is 1 sigma about that, or 1.5 , or 2? I really don't know. And then how big is sigma? My gut tells me it's about 0.1 pH. But again that's my gut.

 

[Gadjobrinus]

AJ, don't know whether you'd be willing to opine (I'd understand if not), but would you put the Extech into the class of cheap, undependable meters? Do you have a recommendation for a portable one, a good one for brewday when one can't conveniently walk to the lab bench? (again, I'd understand if this is a maelstrom you'd rather not join).

 

[ajdelange]

Basically, I guess, what gives us confidence, in a meter?

That's what the stability test is intended to do. See
https://www.homebrewtalk.com/showthread.php?t=302256

 

[TheHopfather]

Interesting topic OP, I was wondering the same thing myself. I've searched and searched for info about mash and room temp pH samples and could never find a straight answer.

@mabrungard - this might be an extremely simple question but does BrunWater calculate the target pH at mash temp or at room temp? I would assume mash temp, which means my room temp samples should be 0.2 ~ 0.3 pH higher then what is actually happening in the mash?

I think my confusion lies in looking at blog posts and such that are showing pH samples reading 5.2. You would think those samples would be cooled, and should be showing higher than that. I'm never quite sure if I should be adjusting my room temp samples down a bit or not.

 

[Gadjobrinus]

That's what the stability test is intended to do. See
https://www.homebrewtalk.com/showthread.php?t=302256

Thanks AJ. Some reading to do, I see.

 

[Big Monk]

PS: Does anyone else have a problem with participants authoritatively posting on this forum while remaining comfortably anonymous behind an assumed avatar? You'll notice that AJ and I stand behind our names for what we say on this forum. It certainly keeps us honest.

I think the varying levels of anonymity here are the most frustrating aspect. Some people, like yourself and AJ are 100% transparent. Others, like myself for instance, are known but not open in the online presence sense.

There are however people posting on all forums, not just here, who use anonymity to present half formed ideas and opinions.

My wife will tell you i'm not an authority on anything besides annoying the crap out of her.

 

[rhys333]

Okay, so my new Thermoworks 8689 comes with ATC. When I test the 7.0 buffer solution my meter recognizes the solution and the display says 6.88 ever time. The manual that comes with my pH meter says its supposed to do this if everything is working well, so this is good.

However, the table on the buffer solution says that at 22 degree C, the readout should be 7.01 instead of 6.88. I've heard that I should use these numbers, so I recalibrate my readout from 6.88 to 7.01. Should I be doing this, or should I trust that ATC has sorted everything out for me and leave the readout at 6.88?

 

[mabrungard]

My wife will tell you i'm not an authority on anything besides annoying the crap out of her.

Then your wife and mine must be sisters!

Regarding the temperature used in Bru'n Water for pH estimation: The instructions in Bru'n Water do emphatically state that all pH prediction is based on room-temperature measurement.

 

[ajdelange]

Okay, so my new Thermoworks 8689 comes with ATC. When I test the 7.0 buffer solution my meter recognizes the solution and the display says 6.88 ever time.

You have purchased a meter that is intended to be calibrated with NIST standard buffers. These are rarely used except in the laboratory. Most meters use NIST traceable 'operational' buffers. With them if the meter sees, during cal, a buffer near 7 it assumes it is a NIST traceable operational buffer and proceeds to do the calibration based on pH values for that meter stored in its memory. If you present such a buffer to your meter it will assume that it is a NIST buffer and proceed to calibrate presumably based on the tables for that buffer unless you tell it that the pH is something different which apparently you must do. Now what I can't tell from the manual is how this entry is treated with respect to temperature variation. Are you supposed to enter the pH of the buffer printed on the bottle label or the pH at the calibration table as obtained from the table often furnished with the buffer?

I would be a little skeptical about readings obtained with this meter (though the error is probably appreciably less than 0.1 pH) and would caution others to avoid it because of this.

Should I be doing this, or should I trust that ATC has sorted everything out for me and leave the readout at 6.88?

It's not the ideal situation by any means but yes, you should do this. Better would be to buy NIST buffers (https://www.inorganicventures.com/productdisplay/ph-686-standard-0) and calibrate the meter as it is intended to be calibrated.

 

[Silver_Is_Money]

The easiest way to clarify this for the OP is to state that a pH of 5.1 measured at roughly 150 degrees F. is the same as a pH of 5.4 measured at roughly 70 degrees F. Both readings are nominally correct with reference/respect to the temperature at which they are taken. But always keep in mind that mash pH software presumes that the reading is to be taken at a nominal 70 degrees F., so if you are measuring pH at mash temperature add ~0.3 to nominally bring your meter readings temperature frame of reference in line with the temperature frame of reference of the software.

https://mashmadeeasy.yolasite.com/

 

[Silver_Is_Money]

Water which is neutral reads as follows: https://chem.libretexts.org/Core/Ph...emperature_Dependence_of_the_pH_of_pure_Water

At 10 degrees C. neutral waters meter measured pH = 7.27
At 25 degrees C. neutral waters meter measured pH = 7.00
At 50 degrees C. neutral waters meter measured pH = 6.63

https://mashmadeeasy.yolasite.com/

 

[ajdelange]

The easiest way to clarify this for the OP is to state that a pH of 5.1 measured at roughly 150 degrees F. is the same as a pH of 5.4 measured at roughly 70 degrees F.

I fear that this may actually confuse him more as they aren't the same at all. The pH actually shifts because the pH depends on the number of protons in solution and the hotter something is the more likely (in most cases0 protons will be jiggled free from acid molecules. IOW the pK's drop as temperature increases.

Both readings are nominally correct with reference/respect to the temperature at which they are taken.

pH is pH. If a meter is properly calibrated (including isoelectric pH) it will read the correct pH at any temperature. But one cannot predict the pH at one temperature from the pH at any other temperature unless he knows the details of the composition of the solution and the behaviour of the individual pKs with temperature. This is, of course, impossible with a mash and so the best we can do is make some assumption about how mash pH actually changes with temperature and this we have to do by making meaurements on mashes or on the grains that go into them. If we measure mash at 150 and find its pH to be 5.1 and then cool it to 70 and find it to be 5.4 we have, for that mash, a glide of 0.3/(80/1.8) = 0.00675 pH/°C. That's not an unusual glide. I use 0.0055 when I don't have actual malt information but I have measured malt glides as large as 0.014 pH/°C but more typically around 0.008 to 0.010 pH/°C.

Thus we cannot say that pH 5.4 measured at 70 is the same as pH 5.1 measured at 150 but we can say that pH 5.4 measured at 70 implies that the pH at 150 is somewhere in the region 4.96 to 5.16.

But always keep in mind that mash pH software presumes that the reading is to be taken at a nominal 70 degrees F., so if you are measuring pH at mash temperature add ~0.3 to nominally bring your meter readings temperature frame of reference in line with the temperature frame of reference of the software.

I would suggest that anyone taking pH readings at mash temperature set the sample aside and record pH at a couple of other temperatures down to room temperature. By so doing he can determine what the glide for his mash actually is and then use that to determine pH at mash temperature from future (for that grist composition) readings at room temperature.

 

[ajdelange]

Water which is neutral reads as follows: https://chem.libretexts.org/Core/Ph...emperature_Dependence_of_the_pH_of_pure_Water

At 10 degrees C. neutral waters meter measured pH = 7.27
At 25 degrees C. neutral waters meter measured pH = 7.00
At 50 degrees C. neutral waters meter measured pH = 6.63

These are half the pK's of pure water at the given temperatures. While pure water would measure those values were it possible to measure it they really represent the neutral pH i.e. the pH at which the concentrations of H+ and (OH)- are equal (and equal to 10^-pK/2). The pKs can be conveniently computed in an Excel spreadsheet from

=4471/A1 +0.01706*A1-6.0875

in which A1 contains the temperature in K (= 273.15 + °C). The pH of pure water at a given temperature is pK/2. So this illustrates the statement I made in the last post that when temperature goes up, pK goes down and H+ ion concentration goes up.

Readers should not expect to be able to obtain any of the numbers from the formula or listed values if attempting to measure the pH of pure (or DI or RO) water as measurement as it is difficult. It is a pretty good insulator and pH measurement relies on current flow. Also it is quickly contaminated by CO2 from the atmosphere which lowers its pH. Air must absolutely be excluded, special buffers are required to calibrate the meter and ion strength adjusters must be added to the sample.