Measuring mash pH and temperature?

The general consensus seem to be that mash pH should be between 5.2 - 5.8
However there seems to be a difference of opinion at what temperature that should be taken at:
According to BREW N WATER (section 2.4) it is at room temperature
However according to a study by BYO which references several sources including John Palmer who I quote "The target mash pH range for every beer, regardless of style is 5.4 - 5.8 at room temperature (5.1 - 5.5 at mash temperature) "
From the above BYO study and from Palmer it would seem that you need to correct the pH meter reading taken at room temperature by subtracting 0.35 ( some discussion on 0.25). You may consider just taking the reading directly from the mash but this gives other undesirable complications as well as the potential to damage the probe.

From my own observations using Brewfather I have consistently been around 0.35 above my target pH in the software, leading me to think that Brewfather calculates for mash temperature. (There is a discussion on this currently on the Brewfather facebook page).
So should I be subtracting 0.35 from the pH meter reading and taking that as my mash pH, the numbers certainly line up nicely or am I off track?

Some ph meters promise automatic temperature correction (atc).

Like you, I hear much on this that I not sully understand....

Regarding pH meters with Automatic Temperature Control...they do not compensate for the change in pH of your wort that occurs as a result of a change in temperature. As the OP's research reveals...there is a 0.3-0.35 variation in the pH of a solution between the mash temperature and room temperature.

All ATC does is compensate for the change in the electrical response of the meter itself with samples of different temperatures.

Oh yeah....measuring at mash temperature will only shorten the life of your pH meter!!

nickjdavis said:

Regarding pH meters with Automatic Temperature Control...they do not compensate for the change in pH of your wort that occurs as a result of a change in temperature. As the OP's research reveals...there is a 0.3-0.35 variation in the pH of a solution between the mash temperature and room temperature.

All ATC does is compensate for the change in the electrical response of the meter itself with samples of different temperatures.

Oh yeah....measuring at mash temperature will only shorten the life of your pH meter!!

Click to expand...

Thanks Nick!

The recommended range for mash pH (5.2 - 5.8 or thereabouts) is for a sample cooled to room temperature.

strange-steve said:

The recommended range for mash pH (5.2 - 5.8 or thereabouts) is for a sample cooled to room temperature.

Click to expand...

So what is Palmer getting at when he says "The target mash pH range for every beer, regardless of style is 5.4 - 5.8 at room temperature (5.1 - 5.5 at mash temperature) "

and the following from BYO

John Palmer was cited in two of the emails that we received at BYO, so I dropped John an email and followed up with a phone call to make sure I was understanding his views. John sent me a presentation he gives about brewing water, “Putting Brewing Water in Perspective”, as a reference.

In this presentation, Palmer cites mash pH ranges in the literature referenced to mash temperature (Bamforth and Briggs), and also cites a pH range in the literature referenced to room temperature (Kunze). He uses a temperature offset of pH 0.25 (more on that later), as opposed to the 0.35 offset from Malting and Brewing Science. Here is a summary of what Palmer reports for the best pH range for optimal extract yield, by source (the range from my answer in question is included in for comparison), and with Palmer’s 0.25 offset included:

Bamforth’s range is: 5.3 to 5.8 (mashtemp) / 5.55 to 6.05 (room temp)

Briggs’ range is: 5.2 to 5.4 (mash temp) / 5.45 to 5.65 (room temp)

Kunze’s range is: 5.25 to 5.35 (mash temp) / 5.5 to 5.6 (room temp)

Lewis’ statement: 5.2 to 5.5 (mash temp) / 5.45 to 5.75 (room temp)

Click to expand...

The term room temperature is hardly scientific. I was always led to believe it was 5.2 - 5.8 at 20c.

@Galena Good question and I certainly can't answer for John Palmer. This point was raised on another forum recently and discussed by several very experienced brewers, some of which with scientific backgrounds, and even so there was a little confusion. However it was suggested that unless a temperature is stated along with the pH then anyone worth listening to would probably be referring to room temperature.

As you know pH varies according to temperature and so is meaningless without a reference temperature. If there isn't one given then convention would suggest the standard reference which is either 20 or 25°C, I'm not really sure which.

The ranges you've quoted above are probably correct, but 5.2 - 5.8 is a large range. Would there be a qualititave difference between a beer mashed at 5.2 pH and the same beer mashed at 5.8 pH? Maybe, I don't really know. If you aimed for a midpoint of 5.5 pH would that be better? Again I don't really know. Is there any software that is accurate enough to worry about an exact target? I'm not sure, but I doubt it. The target range is mostly for enzyme efficiency, so as long as your conversion efficiency is good does it really matter if the pH is on the lower end or the higher end of the range? Maybe, but I don't really know (there's a theme here).

I suppose what I'm saying is if you aim for something like 5.5 pH as measured at room temperature then that's probably good enough. You might be a little off one way or the other but as long as it's only a few 10ths then is it worth worrying about? No surprise, I don't really know, but I don't

This is one part of the brew day I keep forgetting to do. The couple of times I have measured pH it’s been somewhere around the 5.4 mark.
Given that I’ve been hitting my expected OG most brews, I haven’t got to excited about it so far.

I will make the effort next time round, and also to do proper efficiency calculations.

@strange-steve Thanks, I think I need to re-read the mash section of Palmers book, I'm not sure that I'm ready to read "Water"