Mash pH measurement

There's apparently a conflict regarding the recommended way to measure your mash pH. I've seen it mentioned here in one thread or another that your mash pH should be measured at room temperature, which is the method I am accustomed to since I take samples of ~500 F nuclear propulsion plant water but measure it at 25 C. In direct opposition to this Gordon Strong's Brewing Better Beer in which he says that you should measure your mash temperature at mash temp (page 34, first full paragraph, second sentence). I just want to get this cleared up so I make sure I am performing my measurements correctly.

This is one of the very few instances in which I disagree with Gordon. The reasons for doing it at room temperature are clear not the least of which is extension of the life of your electrode. Beyond that going back to the early days samples had to be transported to the laboratory for measurement during which time they cooled and thus pH values reported in the literature are, unless otherwise stated, laboratory temperature pH's. DeClerck specifically mentions that in his book all reported pH values are lab temp. If it's good enough for him it's good enough for me.

Unfortunately, Gordon was not very familiar with this subject when he authored that book. As AJ reiterates, a brewer is far better off measuring mash pH at room temperature for multiple reasons. More over, the pH offset due to the drop from mash temperature to room temperature is relatively consistent. Therefore, it is possible to properly measure pH at room temperature and estimate the actual pH in the hot mash.

But standardizing on a room temperature mash pH measurement is the direction that I and many others have taken.

mabrungard said:

But standardizing on a room temperature mash pH measurement is the direction that I and many others have taken.

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This is bottom line. We want a workable, repeatable process to work from.

Thanks for the clarification. Cheers!

nukebrewer said:

I take samples of ~500 F nuclear propulsion plant water but measure it at 25 C.

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Minor nitpick: You cannot have water at 500° F unless it's under tremendous pressure. Water, of course, turns to steam at 212° F. At normal atmospheric pressure, that's the hottest you can have water, no matter how much heat you apply. Applying more heat just turns it into steam faster, but the water itself can only ever be 212° F.

Of course I don't know but I'm guessing that some pretty hefty pressures might be found in a nuclear propulsion plant.

ajdelange said:

Of course I don't know but I'm guessing that some pretty hefty pressures might be found in a nuclear propulsion plant.

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~1800psi

kombat said:

Minor nitpick: You cannot have water at 500° F unless it's under tremendous pressure. Water, of course, turns to steam at 212° F. At normal atmospheric pressure, that's the hottest you can have water, no matter how much heat you apply. Applying more heat just turns it into steam faster, but the water itself can only ever be 212° F.

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ajdelange said:

Of course I don't know but I'm guessing that some pretty hefty pressures might be found in a nuclear propulsion plant.

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You are indeed correct, AJ. I'm not at liberty to divulge the exact pressure, but it's up there. High enough to keep it from flashing to steam, at least. Also, the pressure needed to keep it from flashing at those temperatures isn't as high as you might think.

ingchr1 said:

~1800psi

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Shhh! That's a government nuclear secret!

nukebrewer said:

Also, the pressure needed to keep it from flashing at those temperatures isn't as high as you might think.

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> 678 psia?

ajdelange said:

> 678 psia?

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That sounds about right. I don't remember the exact number from training but the table I just looked up had it right between 600 psia and 700 psia, but it was too coarse to tell anything more than that.