Is pH stated at room temperature or operating temperature?

[nyakavt]

[quote]Good deal!  So on the strips at mash temp I’m still looking for a value of 5.2 - 5.5?  I might be thinking a bit to hard on this one.
[/quote]

You still want to shoot for 5.1-5.3 on the colorpHast strips regardless of the temp reading (I shoot for 5.0-5.3, which are the strip markings).  The decrease in pH of the solution due to increased temp is offset by an increase in apparent reading on the strip due to the chemical reaction of the litmus paper being affected by temperature.  The -0.3 systematic error inherent to the strips is still present and must be accounted for.  Also be aware that with darker beers the wort color can affect the color of the strip, so make sure to dab it with a towel before trying to read.

[mabrungard]

@hokerer

yep, just look at is as .3 inherent error and .3 temp shift.  The .3’s are in opposite directions so they cancel each other out.

Uh…I don’t use the strips since I have a meter and the fact that they have proven to be inaccurate in the mash, but I don’t think the temp shift enters into this issue.

[tristan]

@nyakavt

You still want to shoot for 5.1-5.3 on the colorpHast strips regardless of the temp reading (I shoot for 5.0-5.3, which are the strip markings).  The decrease in pH of the solution due to increased temp is offset by an increase in apparent reading on the strip due to the chemical reaction of the litmus paper being affected by temperature.  The -0.3 systematic error inherent to the strips is still present and must be accounted for.  Also be aware that with darker beers the wort color can affect the color of the strip, so make sure to dab it with a towel before trying to read.

Thanks!  This is helpful info!

[malzig]

@mabrungard

@hokerer

yep, just look at is as .3 inherent error and .3 temp shift.  The .3’s are in opposite directions so they cancel each other out.

Uh…I don’t use the strips since I have a meter and the fact that they have proven to be inaccurate in the mash, but I don’t think the temp shift enters into this issue.

That’s quite an oversimplification.  If you correct for the pH shift at room temperature, ColorpHast strips are both accurate and precise.

If you don’t calibrate a pH meter you’ll get the wrong pH measurement, but that doesn’t make it inaccurate.

Like any tool, you need to know how to use it.

[euge]

My Brown ale’s mash was 5.2 pH @ 80F on Friday. I’m assuming it was in range.  Just check the pH to make sure the mash isn’t off. If it was off I don’t have anything food-grade to drop it but I could raise it with some bicarb.

[johnf]

@malzig

@mabrungard

@hokerer

yep, just look at is as .3 inherent error and .3 temp shift.  The .3’s are in opposite directions so they cancel each other out.

Uh…I don’t use the strips since I have a meter and the fact that they have proven to be inaccurate in the mash, but I don’t think the temp shift enters into this issue.

That’s quite an oversimplification.  If you correct for the pH shift at room temperature, ColorpHast strips are both accurate and precise.

If you don’t calibrate a pH meter you’ll get the wrong pH measurement, but that doesn’t make it inaccurate.

Like any tool, you need to know how to use it.

How precise? The design precision is .3 pH. That is not as precise as even a very inexpensive meter.

As for accuracy, they measure .3 low at reference temperature, compared to a calibrated meter at reference temperature.

This isn’t a temperature issue, they are just wrong in mash, for whatever reason.

[malzig]

@johnf

How precise? The design precision is .3 pH. That is not as precise as even a very inexpensive meter.

As for accuracy, they measure .3 low at reference temperature, compared to a calibrated meter at reference temperature.

This isn’t a temperature issue, they are just wrong in mash, for whatever reason.

So the pH meter makes an electronic correction for it’s inaccuracy and you have to make a minor mental correction.  After that correction they are both accurate.  Besides, it’s pretty easy to get a bad reading from a pH meter in complex solutions like a mash.  Some pH meters don’t handle ions as simple as sodium very well, let alone complex species like proteins.  Two calibrated pH meters can easily differ by 0.3-0.6 when measuring the same solution.  Don’t be fooled into thinking that, just because you get a digital readout that you know the exact pH of the mash.  You really have no idea if the pH is 5.3 when the meter says 5.3.

The strips will tell you that the mash pH is between 5.3 and 5.6.  When the color is between those two spots you can assume it’s closer to 5.4-5.5.  I think that’s an appropriate precision for brewing, which you may not.