ph in the water calculator is always .2 high

Discussion in 'General Brewing Discussions' started by jay3847, Feb 25, 2020.

  1. jay3847

    jay3847 Member

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    I've been doing salt additions for a couple years now and the calculated ph is always .2ish higher than the actual. I got a good Milwaukee tester with the calibration solutions. I have used RO water, tap water and Crystal Geyser bottled water.

    Any thoughts?
     
  2. Trialben

    Trialben Well-Known Member

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    Trust your PH meter and adjust if need be...
     
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  3. Yooper

    Yooper Administrator
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    We definitely need to look into the results here- .2 is a big difference.
    Can you give me a link to your recipes where this is happening, and the actual pH you achieved?
     
  4. Nosybear

    Nosybear Well-Known Member

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    Yeah, .2 is big. I'm normally within. 02, is that perhaps what you meant?
     
  5. jay3847

    jay3847 Member

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    My last brew was predicted at 5.49 and the meter showed 5.28 after the mash. Temp of the sample was probably 120ish.

    I am certain this is me doing something foolish but looking for some ideas. I started with RO water and added 3 grams of gypsum on 1 gram of calcium chloride to this recipe:
    https://www.brewersfriend.com/homebrew/recipe/view/945096/jay-s-top-crop-test (I'm top cropping some Kveik that I'll dry, just for the hell of it).
     
  6. Nosybear

    Nosybear Well-Known Member

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    That temperature should decrease the pH by about 0.01. Something's off - that mash should land a lot higher than that pH even with the salts. If the error is systematic, that is, if you get a 0.2 error every time, it's something in the meter. Was this the first time you've gotten that error? It also seems that you're adding a lot of salts to a mash this small.

    For the record, 5.28 is not a bad pH for that grist and color. I'd have been shooting for 5.3 in a light mash.
     
  7. HighVoltageMan!

    HighVoltageMan! Well-Known Member

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    I agree, calculators get you close and are estimates, meters tell you what is the actual pH.

    Edit: Measure pH at 70-80F. It will be .2-.3 lower at mash temperatures. This will save on your pH probe. Higher temperatures shorten probe life. A good pH would be 5.3-5.4 at 80F, that translate into 5.1-5.2 at mash temperatures.
     
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  8. jay3847

    jay3847 Member

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    Let me do some tests based on temperature and then will report back. I thought the temperature calibration that comes with the MW102 took care of that.

    Thx.
     
  9. Nosybear

    Nosybear Well-Known Member

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    Nope, it compensates for difference between probe temperature and sample temperature. It does not correct the sample temperature.
     
  10. jay3847

    jay3847 Member

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    Well, that might explain that. Like I said, I must have been doing something stupid.
     
  11. J A

    J A Well-Known Member

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    I've gotten very similar results consistently, but I've assumed that it's just because I'm too lazy to calibrate my meter. I'll have to start looking at the process more carefully.
     
  12. jay3847

    jay3847 Member

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    So, I did the test to see the impact of cooling on the measured ph.

    I heated some tap water and then measured as a cooled the water in stages
    • Temp 153 ph 7.64
    • Temp 137 ph 7.78
    • Temp 122 ph 7.87
    • Temp 110 ph 7.89
    • Temp 85 ph 7.91
    I repeated the test with a different starting ph and go very similar results.

    Soooo, I can either cool the runoff down before testing, or just add .26 to the ph depending on the temp of the sample.
     
  13. Nosybear

    Nosybear Well-Known Member

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    Cool the runoff, or at least a sample. More accurate and easier on the probe.
     
  14. Yooper

    Yooper Administrator
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    Make sure you’re checking mash pH about 10-15 minutes in, not after the mash. The pH will continue to fall a bit throughout the mash.

    Also, don’t stick your pH meter into something so hot!!!!!! You’ll ruin the electrode. Measurements are always done at room temperature. ALWAYS. Even if you have ATC, it won’t protect your meter from those high temperatures. ATC means that the meter will adjust to temperatures variations in the sample, say like from 68F to 72F, not that you should stick the probe into hot samples!

    Cool your sample. I use a shot glass to hold the mash liquid. Cool that in a little ice water bath too under 80 degrees. THEN take the pH. Make sure you don’t have any grain in the sample.
     
  15. jay3847

    jay3847 Member

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    I have been testing at 15 minutes and that is why I wanted to get this right, and I also have the obligatory shot glass for ph measurements! I'll cool the shot glass in advance so it will cool the sample faster to room temperature.

    Thank you, all!
     
  16. Yooper

    Yooper Administrator
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    The pH difference with a sample taken at 155 and one taken at 70 degrees is huge. A mash temp pH should be a approximately .25 lower than a room temperature mash pH.

    Any time pH numbers are given, it’s referring to the room temperature reading. 20 C is the standard.
     

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