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BrewLogue
New Member
Username: Brewlogue
Post Number: 25
Registered: 11-2008
Posted From: 96.251.130.97
| | Posted on Thursday, March 04, 2010 - 08:00 pm: | 
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A guy at the homebrew store mentioned that mash pH is .35 higher at room temperature than it is at mash temp. After I thought about it, I think I remember reading that somewhere. Does this sound right?
Also, the ESB that I have mashing right now measured 5.5 at 75 degrees, so I guess that puts me right where I want to be. |
Bill Pierce
Moderator
Username: Billpierce
Post Number: 11371
Registered: 01-2002
Posted From: 24.141.103.148
| | Posted on Thursday, March 04, 2010 - 08:27 pm: |
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John Palmer says that the pH will read about 0.3 higher at mash temperature than at room temperature. My typical procedure is to take a sample of the mash liquid with a deep spoon and blow on it (like hot soup) until it is at least cool enough to touch, then measure it with my pH meter that is temperature compensated from 5 to 50 degrees C (41-122 F). That way I haven't worried about adjusting the readings; I would be more concerned if I used pH strips inserted directly into the hot mash. |
michael atkins
Advanced Member
Username: Mga
Post Number: 756
Registered: 11-2003
Posted From: 204.26.73.111
| | Posted on Thursday, March 04, 2010 - 09:18 pm: |
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Brew --- Handy tip for easy reference.
I sometimes forget usefull facts given to me at the LHBS, or which way to adjust data or measurements or fail to remember things posted earlier on this board. Instead of always searching the B&V board I use this handy method.
The following is an excerpt that I copied and pasted into the recipe notes of my pro mash program. If you use pro mash just set up a new recipe, enter the notes and paste. Then title it as "AA Mash PH". That way these handy references are always available. Putting AA in front of the title always keeps these tips at the front of the file and easy to find. I have them for several things such as "AA Making a Starter.rec", "AA Lime Water calculations.rec", "AA Carbon Recipe.rec", "AA Mash PH.rec", etc.
And as Bill Said even back in 2007---
"At room temperature, the mash pH should be in the range of 5.2 - 5.6. If your meter is not temperature compensated (or you are using pH strips) and the mash liquid is still warm, adjust that downward to 4.9 - 5.3. As Chris says, you can prolong the life of the meter electrode by allowing the liquid to cool (I just use a spoon and blow on it for 15-20 seconds) before taking a reading."
"(Message edited by BillPierce on July 13, 2007)"
You would think that the PH adjustment or formula for making a starter would be easy to remember, but if you drink as much beer as I have in my lifetime you may someday be making notes also! |
BrewLogue
Junior Member
Username: Brewlogue
Post Number: 26
Registered: 11-2008
Posted From: 96.251.130.97
| | Posted on Thursday, March 04, 2010 - 09:29 pm: |
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Well, I've been using my new pH meter, and it is temperature compensated. Does that mean that my mash was accurately measured at 5.5? Of course, 5.5 is within range, but if that is the true pH, shouldn't it ideally be between 5.2-5.3? |
Bill Pierce
Moderator
Username: Billpierce
Post Number: 11372
Registered: 01-2002
Posted From: 24.141.103.148
| | Posted on Thursday, March 04, 2010 - 09:50 pm: |
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Assuming that the temperature of the sample you are measuring is within the temperature compensation range of your meter, the mash pH reading should be bewween 5.2 and 5.6. I would consider 5.5 to be well within the correct range. There's an old engineer's adage that perfect is the enemy of the good; don't obsess about adjusting it exactly between 5.2 and 5.3, |
michael atkins
Advanced Member
Username: Mga
Post Number: 758
Registered: 11-2003
Posted From: 204.26.73.111
| | Posted on Thursday, March 04, 2010 - 09:54 pm: |
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The instructions on my refractometer say that the MR Milwaukee series will read accurately at 20C (68F). Those with ATC (automatic temperature compensation) adjust automatically within the 10-30C (50-86F) range. |
BrewLogue
Junior Member
Username: Brewlogue
Post Number: 27
Registered: 11-2008
Posted From: 96.251.130.97
| | Posted on Thursday, March 04, 2010 - 10:42 pm: |
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Good info. Thanks! |
Bill Pierce
Moderator
Username: Billpierce
Post Number: 11373
Registered: 01-2002
Posted From: 24.141.103.148
| | Posted on Thursday, March 04, 2010 - 11:23 pm: |
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We're discussing pH measurement, Michael, rather than specific gravity, although what you say about temperature compensation applies to refractometers as well. It's somewhat less of an issue with a refactometer because the very small sample rather quickly cools to the ambient temperature of the glass objective. |
Tim Wi
Senior Member
Username: Riverkeeper
Post Number: 1054
Registered: 03-2005
Posted From: 75.65.152.154
| | Posted on Friday, March 05, 2010 - 12:51 am: |
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For all practical purposes, pH dose not change with temp (it actually does, decreasing with increasing temp, but the magnitude of change is small enough that it can be ignored, ESPECIALLY in a beer wort with lots of buffering potential)
The magnitude of difference cited above is due to the instrument.
test strips and simple meters are calibrated at a particular temp. It is only at that temp that they are most accurate. The further from this optimum, the greater the inaccuracy
Meters that compensate for temparature are calibrated for a range of termperatures, and are able to adjust output based on the input from its temp probe "on the fly". |
Denny Conn
Senior Member
Username: Denny
Post Number: 7362
Registered: 01-2001
Posted From: 75.145.77.185
| | Posted on Friday, March 05, 2010 - 07:53 pm: |
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Take a look here, and at some of Ki's other articles on pH....
http://braukaiser.com/wiki/index.php?title=An_Overview_of_pH |
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