Yet more evidence that commercial brewers do not mash at 5.2 to 5.6 pH ...

[Silver_Is_Money]

So by that definition, and assuming Die_beerery is using it correctly, and I’m sure he is, the value of 5.4 is the true pH as measured at mash temp

Presuming that @Die_Beerery is measuring at room temperature this is not correct. Wort is factually more acidic at higher temperatures due to there being a higher level of dissociation of H+ ions into solution at higher temperatures. An altered slope is required of the pH meter to correct for temperature differences such that it can assure us that it is both reading and presenting us with the correct (and noticeably more acidic, thus lower) pH at mash temperature, and ATC accomplishes this slope alteration so the meter user does not need to resort to doing the slope correcting math himself/herself. ATC does not fake a room temperature reading at mash temperature (as most falsely presume that it does). If the pH of a sample is factually 5.1 at mash temperature and also factually 5.4 at room temperature, then an ATC meter will present you with a true reading of 5.1 at mash temperature and a true reading of 5.4 at room temperature. A non-ATC meter will however be thrown off at mash temperature if calibrated at room temperature, and it will come with instructions as to how to correct its reading at mash temperature such that after the application of said math you will correctly derive a true and factual answer of 5.1 pH.

What is not known is the room temperature to mash temperature differential across a nominal sample reading temperature differential/span of ~45 degrees C. Above I used a mid-range 0.30. Some say to use 0.25 and some say to use 0.35. That is the only controversy yet to be resolved.

 

[TheMadKing]

Presuming that @Die_Beerery is measuring at room temperature this is not correct. Wort is factually more acidic at higher temperatures due to there being a higher level of dissociation of H+ ions into solution at higher temperatures. An altered slope is required of the pH meter to correct for temperature differences such that it can assure us that it is both reading and presenting us with the correct (and noticeably more acidic, thus lower) pH at mash temperature, and ATC accomplishes this slope alteration so the meter user does not need to resort to doing the slope correcting math himself/herself. ATC does not fake a room temperature reading at mash temperature (as most falsely presume that it does). If the pH of a sample is factually 5.1 at mash temperature and also factually 5.4 at room temperature, then an ATC meter will present you with a true reading of 5.1 at mash temperature and a true reading of 5.4 at room temperature. A non-ATC meter will however be thrown off at mash temperature if calibrated at room temperature, and it will come with instructions as to how to correct its reading at mash temperature such that after the application of said math you will correctly derive a true and factual answer of 5.1 pH.

What is not known is the room temperature to mash temperature differential across a nominal sample reading temperature differential/span of ~45 degrees C. Above I used a mid-range 0.30. Some say to use 0.25 and some say to use 0.35. That is the only controversy yet to be resolved.

Thanks! That jives with what I found on the thermofisher website and makes sense.

But he stated that those readings are from probes in-line with his process, so i don’t think your first sentence is correct. If the probes are in-line then it would not be easy to cool only the wort stream passing by the pH probe, so i believe he is measuring at mash temperature and relying on ATC to ensure the reading is correct.

@Die_Beerery can you confirm or refute this?

So based on your last paragraph the real issue is that you can’t prescribe a generic/nominal room temperature pH value that is “good enough” for home brewers because it could be off because the slope shifts with temperature?

 

[Vale71]

ATC will only correct for the slope change due to the effect of different temperatures on the probe's response. It will not correct for the actual temperature-dependent PH shift of the solution as this depends on the actual composition of the solution which cannot be known to the PH meter, obviously. Basically ATC will adjust for the temperature-induced instrumental error, both during calibration and measurement, and for nothing else.

 

[Miraculix]

Just to throw one thing in which got stuck to my head and somebody might not know.

"Converting" a pH from one temperature to another is not the same thing as for example, converting a gravity from one temperature to another to get an idea about the sugar content of the liquid.

pH is a logarithmic scale of h3o+ ions in solution, which literally changes with temperature. This means that within the same liquid at different temperatures, there is a different amount of h3o+ ions present which therefore effect the chemical reactions within the liquid differently at different temperatures.

However, the amount of sugar in solution stays the same within the liquid at different temperatures, all that changes is the gravity, not the amount of sugar.

 

[dmtaylor]

A non-ATC meter will however be thrown off at mash temperature if calibrated at room temperature, and it will come with instructions as to how to correct its reading at mash temperature such that after the application of said math you will correctly derive a true and factual answer of 5.1 pH.

Oh... yeah!!! NOW I kind of remember... I already learned about this slope thing a long time ago, and so instead of calibrating my pH meter at 6.86 and 4.01, I aim to calibrate it using those same solutions but assuming that while at room temperature they are instead at 6.90 and 4.00. If I did all of this correctly, it essentially allows me to calibrate for measurement of pH at mash temperature but using room temperature cal solutions. At some point I should probably double-check the numbers on all this because although I've been doing things this way for many years, I can't remember now how I even figured it out way back when. I thought the manufacturer provided these corrections, but now I can't find that documentation anymore. (On the other hand, since we're talking about differences of hundredths of a pH point, I honestly don't even really care anyway! Like I always say... "close enough" is close enough!)

 

[Silver_Is_Money]

For the case of @Die_Beerery calibrating at room temperature and then inline measuring a pH of 5.4 at mash temperature, then he is 'effectively' mashing at a room temperature measured pH of around 5.7. Only he can clarify this for us.

 

[dmtaylor]

But he stated that those readings are from probes in-line with his process, so i don’t think your first sentence is correct. If the probes are in-line then it would not be easy to cool only the wort stream passing by the pH probe, so i believe he is measuring at mash temperature and relying on ATC to ensure the reading is correct.

@Die_Beerery can you confirm or refute this?

My thoughts exactly. I wanted to assume since it's in-line that the pH was reported at actual temperature... but without double-checking with D_B, I didn't want to assume either.

 

[TheMadKing]

For the case of @Die_Beerery calibrating at room temperature and then inline measuring a pH of 5.4 at mash temperature, then he is 'effectively' mashing at a room temperature measured pH of around 5.7. Only he can clarify this for us.

That was what i was saying earlier, sorry if i wasn’t being clear... still on my first cup of coffee [emoji4]

 

[dmtaylor]

For the case of @Die_Beerery calibrating at room temperature and then inline measuring a pH of 5.4 at mash temperature, then he is 'effectively' mashing at a room temperature measured pH of around 5.7. Only he can clarify this for us.

*5.65

 

[dmtaylor]

That was what i was saying earlier, sorry if i wasn’t being clear... still on my first cup of coffee [emoji4]

I don't drink coffee until I get to work, where it's free and terrible.

 

[Silver_Is_Money]

I don't drink coffee until I get to work, where it's free and terrible.

I remember those days!

 

[dmtaylor]

I remember those days!

Only 10 more years to 55.

 

[TheMadKing]

So am I understanding correctly that you can only approximate the pH conversion from one temperature to another because the actual pH is changing and that change is dependent on the composition of the solution. So a pH conversion from 20C to 65C wouldn't be the same for a dark wort and a light wort for example?

So why isn’t it just recommended for homebrewers to measure at mash temp with an ATC instrument calibrated at room temp?

I understand that this will decrease the life of the pH probe, and that lab convention says that pH should be measured at room temperature, but are those the only reasons?

 

[dmtaylor]

So am I understanding correctly that you can only approximate the pH conversion from one temperature to another because the actual pH is changing and that change is dependent on the composition of the solution. So a pH conversion from 20C to 65C wouldn't be the same for a dark wort and a light wort for example?

So why isn’t it just recommended for homebrewers to measure at mash temp with an ATC instrument calibrated at room temp?

I understand that this will decrease the life of the pH probe, and that lab convention says that pH should be measured at room temperature, but are those the only reasons?

Everybody is so concerned about the damned probe. But look..... I've been measuring at mash temperature of about 150 F for dozens of batches, using my CHEAP $14 Chinese meter from Amazon, and it works great to this day. When the damn thing dies, which I've little doubt that eventually it will, it's pretty friggin cheap to buy a new one, and NOT one of these stupid $100 models.

And anyway... even after all of my geeking out on all this stuff, I'm still very unconvinced that pH even matters much at all anyway. I may change my tune later. But what I've discovered recently is that overall my beers were better BEFORE I cared about pH than after. And only after I learned the 5.6 thing have my beers improved to not-seen-in-a-long-time levels. But I've only brewed a couple batches like that so far. More data needed.

P.S. I believe there is indeed a grist, recipe, crop component to pH as well. pH can come out slightly different every time you brew, even the same recipe.

 

[Silver_Is_Money]

What is not known is the room temperature to mash temperature differential across a nominal sample reading temperature differential/span of ~45 degrees C. Above I used a mid-range 0.30. Some say to use 0.25 and some say to use 0.35. That is the only controversy yet to be resolved.

It may be that for some meters the differential works out to be 0.25, and for others 0.35 (or anything inbetween). ???

Or as @TheMadKing suggests, there may be Grist/Wort/Wort_density related (inter)dependence to some degree as well.

And @Miraculix reminds us that ideal temperature differential linearity from degree to degree to degree... may be hard to come by when playing with logarythims.

 

[Silver_Is_Money]

Speaking of pH meters, I had been in the market for one, and in the process of searching I recently noticed this meter (see link below) for which, oddly enough, it sells at a broad range of lab supply stores for ballpark $400 (give or take ballpark $35) when purchased with bottled calibrating solutions and bundled in a cheep plastic carrying case, but then suddenly there it was, new and from the manufacturer itself with free shipping on Amazon for only $78 if purchased without the case, and with calibration solution building tablets instead of bottled and ready-made calibration solutions. I took a chance and ordered it, and a few days later it arrived. But in the mean time I checked back on Amazon, and now the very same "without case" meter suddenly costs $345. I haven't used it yet.... Fingers are crossed.

https://www.amazon.com/LaMotte-5-00...er+"no+case"&qid=1573045112&sr=8-1-fkmr1&th=1

 

[hopjuice_71]

So am I understanding correctly that you can only approximate the pH conversion from one temperature to another because the actual pH is changing and that change is dependent on the composition of the solution. So a pH conversion from 20C to 65C wouldn't be the same for a dark wort and a light wort for example?

In theory, you are correct. Different buffering compounds have different thermodynamics of ionization. This means there is a temperature dependence of where the equilibrium lies between free and bound protons, and this differs between buffering compounds. If you know exactly what your buffer is and what the thermodynamics of ionization are, you can predict the temperature dependence of pH. The mash is a bit of a black box in this respect and of course it changes with different grists, water chemistries, etc, so really precise predictions of pH at different temperatures would be difficult. @Vale71 already hinted at all this.

I'm with @dmtaylor. I find close enough in the mash works. Adjusting pH in the kettle seems more important.

 

[Robert65]

my CHEAP $14 Chinese meter from Amazon

Link please?

 

[Vale71]

It may be that for some meters the differential works out to be 0.25, and for others 0.35 (or anything inbetween). ???

Again, the ATC function already knows how the particular probe behaves and compensates for that. It follows that different meters will have different ATC parameters programmed in if their probes behave differently respective temperature change.
The change in PH value in the solution with temperature on the other hand is an actual change and is only dependent on the nature of the solution and not the measuring instrument. It's to be expected that different worts of different composition and/or density will behave differently so that a universal correction value simply cannot be determined.

 

[Robert65]

It's to be expected that different worts of different composition and/or density will behave differently so that a universal correction value simply cannot be determined.

I have been banging my head against a brick wall trying to explain this to people for years. Good luck getting them to listen.

 

[hopjuice_71]

I have been banging my head against a brick wall trying to explain this to people for years. Good luck getting them to listen.

In fairness, it is a difficult concept. Even if one understands what pKas mean grasping how and why these change with temperature is a whole other level. Throw in mixed buffering systems and the mind gets blown

 

[TheMadKing]

Well you guys have convinced me that there may have been a misinterpretation of the literature early in the homebrewing renaissance and I'm going to try it your way for a few batches, starting with my Helles Bock on Saturday.

I'll be using bru'n water to aim for a target pH of 5.7. I'm working on the assumption that Bru'n water's target pH is intended to be measured at room temperature. So that should be within the range of 5.2-5.4 in my mash

I will then attempt to acidify using biological acidification (Sauergut) to 4.9-5.1 in the kettle pre-boil, and 4.8-5.0 post-boil - This will be the third time I've made this recipe so I have a fairly good feel for how it should come out. Nothing will be objectively determined by this, but if it makes a bad beer at least I'll have something to look harder at.

 

[ScrewyBrewer]

If a mash pH prediction for a given grain bill is 5.3 at 77F/25C a sample taken at 152F/66.7C will be 5.00. With the pH meter calibrated with calibration solutions at 77F/25C for the former and at 152F/66.7C for the latter.

 

[Miraculix]

Well you guys have convinced me that there may have been a misinterpretation of the literature early in the homebrewing renaissance and I'm going to try it your way for a few batches, starting with my Helles Bock on Saturday.

I'll be using bru'n water to aim for a target pH of 5.7. I'm working on the assumption that Bru'n water's target pH is intended to be measured at room temperature. So that should be within the range of 5.2-5.4 in my mash

I will then attempt to acidify using biological acidification (Sauergut) to 4.9-5.1 in the kettle pre-boil, and 4.8-5.0 post-boil - This will be the third time I've made this recipe so I have a fairly good feel for how it should come out. Nothing will be objectively determined by this, but if it makes a bad beer at least I'll have something to look harder at.

Don't assume. Ask @mabrungard himself!

 

[Silver_Is_Money]

I will then attempt to acidify using biological acidification (Sauergut) to 4.9-5.1 in the kettle pre-boil, and 4.8-5.0 post-boil - This will be the third time I've made this recipe so I have a fairly good feel for how it should come out. Nothing will be objectively determined by this, but if it makes a bad beer at least I'll have something to look harder at.

I would target 5.1 pH as measured at 20 degrees C. (in full compliance with EBC standard # 8.17) in the pre-boil Wort. That way, even if the post boil and cooling (to 20 degrees C.) Wort misses the 5.1 target by a full tenth, it will still be within the accepted 5.0 to 5.2 pH range which is considered to be the ideal at this juncture.

5.7 isn't a bad 20 degree C. measured target for the mash, but if it was me I might trim the target back to 5.65.

 

[TheMadKing]

If a mash pH prediction for a given grain bill is 5.3 at 77F/25C a sample taken at 152F/66.7C will be 5.00. With the pH meter calibrated with calibration solutions at 77F/25C for the former and at 152F/66.7C for the latter.

But your 5.3 value is never measured by a meter, it is calculated only. So based on that calculated value how can you conclusively state that it will be 5.0 at mash temp, since the actual pH changes non-linearly and the rate of change is dependent on the ions in solution?

Don't assume. Ask @mabrungard himself!

It states that in his water information page on his website

" A slightly acidic mash pH of between 5.2 and 5.8 (measured at room-temperature) improves the enzymatic processes during mashing.... Mash pH measurements vary with the temperature of the mash. There are two components to this pH measurement variation. The first component is a chemical change caused by the change in the energy in the water that makes it easier to split hydrogen protons from acidic molecules in the mash. A hotter mash is therefore a bit more acidic. The second component is due to the change in electrical response of the pH meter probe electrodes with temperature. These two factors produce a mash pH measurement (when using a pH meter) that measures about 0.2 to 0.3 units lower at 150°F than at room temperature. Therefore, it is important to standardize the temperature at which mash pH is measured. All pH readings presented on this page assume measurement at room-temperature [between 20°C and 25°C (68°F to 77°F)]. "

I would be very surprised if Martin hadn't thought all of this through very thoroughly and has not already gone-round this circle with AJ a few times in developing his recommendations though. So I'm more inclined to believe we are missing something than both he and AJ are wrong.

 

[Silver_Is_Money]

If a mash pH prediction for a given grain bill is 5.3 at 77F/25C a sample taken at 152F/66.7C will be 5.00. With the pH meter calibrated with calibration solutions at 77F/25C for the former and at 152F/66.7C for the latter.

This assessment is close enough to spot on in my book, since it takes the middle ground approach.

 

[ScrewyBrewer]

But your 5.3 value is never measured by a meter, it is calculated only.

@TheMadKing you miss the point and so the confusion.

The pH meter is first calibrated with calibration solutions at 77F/25C for the sample taken at 77F/25C .

It is again calibrated with calibration solutions at 152F/66.7C for the sample taken at 152F/66.7C.

 

[Robert65]

Here's a thought on why a room temperature measurement might be particularly useful. Those of us who do step mashes would obviously measure a different pH at each different temperature through the program. But presumably samples taken at any or all of those temperatures would give the same value when cooled to the same reference temperature, even though there may be no way to predict the correlation. So the room temperature measurement would still be a fixed reference point for the particular mash, and changes due to a particular temperature can be ignored. We can empirically correlate room temperature mash pH with effects on the wort and beer, without worrying about the actual chemistry at mash temperature.

 

[TheMadKing]

@TheMadKing you miss the point and so the confusion.

The pH meter is first calibrated with calibration solutions at 77F/25C for the sample taken at 77F/25C .

It is again calibrated with calibration solutions at 152F/66.7C for the sample taken at 152F/66.7C.

Sorry, I'm not trying to be dense, but your original statement did not contain a sample taken at 77F/25C - it contained a value calculated at that temperature, and then a sample taken and measured at a different temperature, which is all I'm confused about