Author Topic: Mash ph Delta Discrepancy  (Read 542 times)

Offline Brent

  • 1st Kit
  • *
  • Posts: 2
  • TenSpeed Brewer
    • View Profile
Mash ph Delta Discrepancy
« on: March 13, 2018, 05:56:34 PM »
On my last brew day I used a cooled sample of the mash liquid to test the delta between the mash temp ph and the room temperature ph.

My results were confusing since John Palmer and others claim the difference should be .35 where my delta was double that at .7

Has anyone else experienced this difference? And what could be causing this?

Mash ph @ 154*F was 5.1 and the room temperature ph @ 75*F was 5.8
Brent

Offline ynotbrusum

  • I spend way too much time on the AHA forum
  • ********
  • Posts: 2885
    • View Profile
Re: Mash ph Delta Discrepancy
« Reply #1 on: March 13, 2018, 06:02:09 PM »
Here comes a potential rabbit hole - I think all pH measurements are intended to be done at room temperature...so did you cool the mash sample to room temperature?  If not, that could be an issue for comparison.  Also, I hear tell that it shortens the life of the probe to use mash temperatures for readings.
Hodge Garage Brewing: "Brew with a glad heart!"

Offline dmtaylor

  • Official Poobah of No Life.
  • *
  • Posts: 3388
  • Two Rivers, WI
    • View Profile
    • Manty Malters - Meet the Malters! - Dave Taylor
Re: Mash ph Delta Discrepancy
« Reply #2 on: March 13, 2018, 06:36:03 PM »
The difference that Palmer and I get is more like 0.25, not 0.35 and certainly not 0.70.  Most likely operator error.  Try again next batch and see if it comes down closer to 0.25 difference.

I continue to measure at mash temperature because it's easier and gives instant results.  If/when my probe dies, I might reevaluate.  However so far it works just fine after about a dozen batches measuring hot.
Dave

The world will become a much more pleasant place to live when each and every one of us realizes that we are all idiots.

Offline denny

  • Administrator
  • Retired with too much time on my hands
  • *****
  • Posts: 19762
  • Noti OR [1991.4, 287.6deg] AR
    • View Profile
    • Dennybrew
Re: Mash ph Delta Discrepancy
« Reply #3 on: March 13, 2018, 07:30:13 PM »
On my last brew day I used a cooled sample of the mash liquid to test the delta between the mash temp ph and the room temperature ph.

My results were confusing since John Palmer and others claim the difference should be .35 where my delta was double that at .7

Has anyone else experienced this difference? And what could be causing this?

Mash ph @ 154*F was 5.1 and the room temperature ph @ 75*F was 5.8

Reality often astonishes theory.
Life begins at 60.....1.060, that is!

www.dennybrew.com

The best, sharpest, funniest, weirdest and most knowledgable minds in home brewing contribute on the AHA forum. - Alewyfe

"The whole problem with the world is that fools and fanatics are always so certain of themselves, and wiser people so full of doubts." - Bertrand Russell

Offline Robert

  • Brewmaster General
  • *******
  • Posts: 2021
    • View Profile
Re: Mash ph Delta Discrepancy
« Reply #4 on: March 13, 2018, 08:05:27 PM »
Your experience is not odd, Brent.  You generally see it stated that the delta is "usually around 0.3" or something like that.  Any examples of measured data sets I've seen shows this displacement is really all over the place, from maybe 0.15 up to the 0.7 range you saw.  There is no simple conversion formula, as every mash is different, depending on grist, water chemistry, temperature of the sample, market trends in Bitcoin futures, and feng shui  ;).  That's why, since pH in brewing always refers to pH at STP reference conditions,  that's where you measure it.  (And because that tiny thin glass bulb of reference solution really hates extreme temps.  I killed a couple of expensive probes really fast by trusting a conversion formula Palmer published, thinking it would be neat to just dip it in the mash.  And the formula was always wrong.)
Rob Stein
Akron, Ohio

I'd rather have questions I can't answer than answers I can't question.

Offline Brent

  • 1st Kit
  • *
  • Posts: 2
  • TenSpeed Brewer
    • View Profile
Re: Mash ph Delta Discrepancy
« Reply #5 on: March 14, 2018, 10:10:14 PM »
Thanks, I will continue to monitor and experiment and hopefully my delta settles down to the .25 as Dave has experienced.

Kal from the Electric Brewery seems to measure his ph right in the mash tun (like I have been doing) and he shoots for 5.2 which according to theory would be 5.45 or 5.5.

I suppose a rapid cool down of the wort sample is best so not as to lose precious time in the proper ph zone.
Any suggestions on that process?

Brent
Brent

Offline EnkAMania

  • Assistant Brewer
  • ***
  • Posts: 173
    • View Profile
Re: Mash ph Delta Discrepancy
« Reply #6 on: March 14, 2018, 10:12:33 PM »

I suppose a rapid cool down of the wort sample is best so not as to lose precious time in the proper ph zone.
Any suggestions on that process?

Brent

I have a bowl of nearly freezing water.  I have the sample in a little glass.  Stir around in the cold water for 3 minutes and I have a room temperature sample.
Some day we'll look back on this and it will all seem funny

Offline BitterItDown

  • Cellarman
  • **
  • Posts: 59
    • View Profile
Re: Mash ph Delta Discrepancy
« Reply #7 on: March 15, 2018, 12:29:59 AM »
Perhaps this link will help explain:

https://www.omega.com/Green/pdf/pHbasics_REF.pdf

Offline dmtaylor

  • Official Poobah of No Life.
  • *
  • Posts: 3388
  • Two Rivers, WI
    • View Profile
    • Manty Malters - Meet the Malters! - Dave Taylor
Re: Mash ph Delta Discrepancy
« Reply #8 on: March 15, 2018, 01:05:05 AM »
Perhaps this link will help explain:

https://www.omega.com/Green/pdf/pHbasics_REF.pdf

That's cool, thanks for sharing.

Hmm... seems that when measuring at 65 C (149 F), at a pH of about 5, we should be adding +0.24.

Haven't we seen a number like that thrown around before?  :)
Dave

The world will become a much more pleasant place to live when each and every one of us realizes that we are all idiots.

Offline thcipriani

  • Assistant Brewer
  • ***
  • Posts: 182
    • View Profile
Re: Mash ph Delta Discrepancy
« Reply #9 on: March 15, 2018, 06:10:24 PM »
Also does your meter do ATC at all?

My limited understanding is that when folks say the pH differs by 0.35ish at room temp vs mash temp they mean the actual pH of the solution is different. It's also true that meters have to perform their own internal correction for temperture as well. That is, a meter with ATC will show the difference in the actual pH (~0.35) and a meter without it will have undefined behavior and just be unpredictably incorrect.

If your meter doesn't have ATC: might explain it. If it does: then TIL that ~0.35 might not be normal pH difference. I've never actually tried this with my ATC meter (as others have pointed out folk wisdom is it shortens probe life).
Tyler Cipriani
Longmont, CO
http://gangsta.party/

Offline denny

  • Administrator
  • Retired with too much time on my hands
  • *****
  • Posts: 19762
  • Noti OR [1991.4, 287.6deg] AR
    • View Profile
    • Dennybrew
Re: Mash ph Delta Discrepancy
« Reply #10 on: March 15, 2018, 07:52:04 PM »
Also does your meter do ATC at all?

My limited understanding is that when folks say the pH differs by 0.35ish at room temp vs mash temp they mean the actual pH of the solution is different. It's also true that meters have to perform their own internal correction for temperture as well. That is, a meter with ATC will show the difference in the actual pH (~0.35) and a meter without it will have undefined behavior and just be unpredictably incorrect.

If your meter doesn't have ATC: might explain it. If it does: then TIL that ~0.35 might not be normal pH difference. I've never actually tried this with my ATC meter (as others have pointed out folk wisdom is it shortens probe life).

ATC corrects for the temp of the meter, not the sample.
Life begins at 60.....1.060, that is!

www.dennybrew.com

The best, sharpest, funniest, weirdest and most knowledgable minds in home brewing contribute on the AHA forum. - Alewyfe

"The whole problem with the world is that fools and fanatics are always so certain of themselves, and wiser people so full of doubts." - Bertrand Russell