[mabrungard]

I find that now that I store my probe in storage solution, the calibration settings change very little.  This suggests that if you store the probe properly, the meter should maintain its calibration better.  I still check my calibration every session since its providing important information for my mash acidity vs pH calibration data set.  

Another consideration is that as the probe ages, its susceptability to calibration drift is greater.  I would check the calibration every several sessions in any case.

[Thirsty_Monk]

Can you buy a replacement probe for this pH meter?

[narcout]

Can you buy a replacement probe for this pH meter?

Yes.

[Thirsty_Monk]

Cool, I have 10 more test strips. I am due to get me a pH meter

[blatz]

little confused here - I brewed a fest yesterday - pH read 5.61 at room temp and 5.44 at mash temp.  I know its a little high, but I think I'm okay - gravity etc was fine.  More important, does that differential seem right?  I thought it should be 0.3 difference between mash and room temp readings?

[blatz]

also - is there a good reason why I couldn't save some of the calibration solutions (in white labs tubes) for future use? 

[bluesman]

little confused here - I brewed a fest yesterday - pH read 5.61 at room temp and 5.44 at mash temp.  I know its a little high, but I think I'm okay - gravity etc was fine.  More important, does that differential seem right?  I thought it should be 0.3 difference between mash and room temp readings?

I wouldn't worry too much about that difference, although I would be curious as to why it varied at that rate. You're within range, so you should be fine with it either way. I assume you calibrated your meter prior to taking your readings?

[mabrungard]

I thought it should be 0.3 difference between mash and room temp readings?

There is disagreement as to the difference in pH between mash and room temperature measurements.  For instance, Malting and Brewing Science states that the difference is about 0.35 units.  You and other sources quote a 0.3 unit difference.  Measurements by AJ Delange and Kai Troester indicate its more like 0.2 units. 

[gordonstrong]

I measured it for my book using lab-grade equipment; it was about 0.3 to 0.35.  But I was measuring distilled water, not mash.  I think AJ was suggesting that it might be less of a difference that way.  I'd like to try some experiments with different liquids and see if it makes a difference.

If you're talking about a 0.05 difference, you also have to look at the precision of your instrument.  Can it resolve to that level?  How is it rated?

Also, you say "mash temps".  It's a curve, so the difference isn't the same across all mash temperatures.  I'd have to go back to check my data to see where it was 0.3 and where it was 0.35, but it was likely in single infusion ranges.

A 0.05 difference in pH isn't going to affect your beer in any meaningful way, so I don't know that it's worth arguing about.

[blatz]

I use the MW 101  http://www.water-testers.com/contents/en-us/p4324_milwaukee_mw101_ph_meter.html

like you said, the more I think about, the less it is worth worrying about.

One thing that was cool - Martin's sheet said the pH at room temp should come out to 5.6, and it did.  Too bad, I forgot to go back and change my salt additions when I rearranged my grist - I would have shot for 5.4-5.5 instead, but all should be good.

[hubie]

I think the temperature dependence depends upon how acidic the solution is, and if that is true (and my subconscious isn't telling me that just to mess around with me), then it should depend upon the mash composition: mashes with highly kilned malts should act different than distilled water.  Of course the chemistry in a mash involves many different compounds with different dissociation rates, some that increase the pH and some that decrease the pH, so the real answer is probably not so neat.

This is why I went into physics.  I much prefer to break the problem down into a simple idealized system:  let's assume a spherical mash tun...

[mabrungard]

I think the temperature dependence depends upon how acidic the solution is

This factor might have some relevance.  I had not thought about it prior.  But, it may not really be that significant since we focus on a relatively narrow pH range for mashing since it tends to optimize our mashing performance.  For those cases where the brewer does not manage their mash pH, then I concur that the acidity and temperature dependence could affect the typical pH offset that has been reported.
 

[narcout]

little confused here - I brewed a fest yesterday - pH read 5.61 at room temp and 5.44 at mash temp.  I know its a little high, but I think I'm okay - gravity etc was fine.  More important, does that differential seem right?  I thought it should be 0.3 difference between mash and room temp readings?

How did you measure the pH at mash temperature?  I have the same meter as you and the maximum temperature compensation is 50 degrees Celsius (122 degrees Fahrenheit).

I've also heard that it isn't good for the probe to immerse it in mash temperature liquids. 

[blatz]

little confused here - I brewed a fest yesterday - pH read 5.61 at room temp and 5.44 at mash temp.  I know its a little high, but I think I'm okay - gravity etc was fine.  More important, does that differential seem right?  I thought it should be 0.3 difference between mash and room temp readings?

How did you measure the pH at mash temperature?  I have the same meter as you and the maximum temperature compensation is 50 degrees Celsius (122 degrees Fahrenheit).

I've also heard that it isn't good for the probe to immerse it in mash temperature liquids. 

154.  yes, I know its bad, but I couldn't help myself. 

[gordonstrong]

I was using gear in a chemistry lab that was rated for those temperatures.  I wouldn't do it on consumer gear that isn't rated for it.