Home Brew Forums > Predicting pH with Brun Water

02-04-2013, 12:51 AM   #11
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Quote:
 Originally Posted by ne0t0ky0 5.12 pH @ 90F corrected is: 5.0793 5.21 ph @ 100F corrected is: 5.1414 5.42 pH @ 97F corrected is: 5.3673
Where did you find this and what is the temp of the correction?

Kai

02-04-2013, 12:54 AM   #12
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Quote:
 Originally Posted by Kaiser Where did you find this and what is the temp of the correction? Kai
http://www.hamzasreef.com/Contents/Calculators/PhTempCorrection.php

And I assume 25C, as if I put that temp in the calculation, it results in the same reading as the input.

02-04-2013, 02:18 AM   #13
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Quote:
 Originally Posted by ne0t0ky0 http://www.hamzasreef.com/Contents/Calculators/PhTempCorrection.php And I assume 25C, as if I put that temp in the calculation, it results in the same reading as the input.
Thanks.

This doesn't apply here. The calculator calculates the temperature depended shift in the probe's response to a given pH. It's the TC function (temperature correction) of a meter that has ATC (Automatic Temperature Correction). The temp dependent pH shift in wort (or any other substance for that matter) is different. It is an actual change in pH and the reason why we want to settle on one temp for pH measurements. I like 25 C since that's the temp at which my calibration buffers are correct.

Kai

02-04-2013, 02:23 AM   #14
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Quote:
 Originally Posted by Kaiser Thanks. This doesn't apply here. The calculator calculates the temperature depended shift in the probe's response to a given pH. It's the TC function (temperature correction) of a meter that has ATC (Automatic Temperature Correction). The temp dependent pH shift in wort (or any other substance for that matter) is different. It is an actual change in pH and the reason why we want to settle on one temp for pH measurements.
Interesting. Could such a correction table be created for wort? or would it not be feasible given all of the variability of the mash composition?

Quote:
 Originally Posted by Kaiser I like 25 C since that's the temp at which my calibration buffers are correct. Kai
Good to know; it's never been clear to me until now that I need to select a target room temperature and use that consistently with the pH measurements.

Thanks!

02-04-2013, 02:27 AM   #15
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Quote:
 Originally Posted by ne0t0ky0 Good to know; it's never been clear to me until now that I need to select a target room temperature and use that consistently with the pH measurements. Thanks!
I seem to remember a private conversation via PM with AJ a while back and this was the issue I remember. Just way too many variables in differing worts.

02-04-2013, 02:33 AM   #16
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Quote:
 Originally Posted by ne0t0ky0 Good to know; it's never been clear to me until now that I need to select a target room temperature and use that consistently with the pH measurements. Thanks!
Just to point out; this is my failure to comprehend what's written quite clearly in the pH Meter Calibratation thread

Quote:
 2. Cool the sample to room temperature, ideally the same temperature as the buffers you used for calibration. This prolongs electrode life and reduces the burden on ATC. If you use a small metal saucepan you can achieve the cooling quickly by immersing it in cool/cold water.

02-04-2013, 02:49 AM   #17
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Quote:
 Originally Posted by ne0t0ky0 Interesting. Could such a correction table be created for wort? or would it not be feasible given all of the variability of the mash composition?
maybe. Someone would have to be willing to subject his/her pH meter probe to high mash temperatures for many different mashes to see what the correlations is and what the variability is.

Kai

02-04-2013, 02:57 AM   #18
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Quote:
 Originally Posted by Kaiser maybe. Someone would have to be willing to subject his/her pH meter probe to high mash temperatures for many different mashes to see what the correlations is and what the variability is. Kai
I'd say go low first and see if a curve developed and then go up.

02-05-2013, 01:40 AM   #19
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I experienced a lower mash pH recently on a recipe with some carafa and crystal malts. I mixed both baking soda and pickling lime in my mashing liquor to raise alkalinity, and also add some sodium, aside from other additions.

The model was fine at 1.2 qt/lbs for the protein rest, but the second infusion to saccharification lead to a lower pH of 5.1. It took a surprising amount of pickling lime to raise to my desired 5.4 pH The water/grist ratio was about 1.8 qt/lbs.

I forgot to note how much pickling lime I added. I normally measure to 0.1 g, but I was hasty to raise my mash pH. In the future, though, I will ensure I have extra lime on hand during mash-in. I'd rather add lime (raise alkalinity, and add calcium), than lower pH with an acid and leave the corresponding anions. Not after all the hassle of RO filtering!

02-05-2013, 01:20 PM   #20
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Quote:
 Originally Posted by lockwom I experienced a lower mash pH recently on a recipe with some carafa and crystal malts. I mixed both baking soda and pickling lime in my mashing liquor to raise alkalinity, and also add some sodium, aside from other additions. The model was fine at 1.2 qt/lbs for the protein rest, but the second infusion to saccharification lead to a lower pH of 5.1. It took a surprising amount of pickling lime to raise to my desired 5.4 pH The water/grist ratio was about 1.8 qt/lbs.
If I'm reading this correctly you struck at protein rest temperature and found the pH OK (which I presume means around 5.4), then infused to step to saccharifcation and found the pH had fallen back to 5.1? Is that correct?

If I am reading that right then something is wrong. It is normal for pH to drift but the rate usually slows dramatically after 15 minutes or so unless you are doing decoctions and even then it isn't likely to be much unless the water is calcium rich. And the drift is usually upward. So if you see a drop of 0.2 - 0.3 after an infusion I'd check the meter. Inexpensive meters drift quite a bit. There is a Sticky here that goes into how to check the stability of your meter.