Strange pH behaviour, or not?

Discussion in 'General Brewing Discussions' started by okoncentrerad, Jan 3, 2019.

  1. okoncentrerad

    okoncentrerad Active Member

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    I did an impromptu mash yesterday evening with the boil early this morning. I think I finished mashing by 10pm and after a short pasteauristion I let it sit in the kettle until 7am today, when I started the boil. Temperature of the wort was down to something like 45C (110F) at that time.

    It's not every time I take pH readings but fairly often, just to see where I'm at. I don't take readings in the beginning or middle of the mash but usually after mash since I don't feel confident enough to adjust on the fly. Yesterday evening I forgot to take a reading so I did it this morning instead. The pH reading was almost 7....close to my water's natural pH of 7.2. The recipe calculator had an estimated pH of 5.6 and I had adjusted the mash water with some lactic acid to get in to the 5.4 area. My first thought was that my pH meter was kaput and/or needed calibration but even after calibration and testing on other fluids it kept showing 7 on my wort and pH after boil read about 6.7.

    So, can anyone explain to me what happend, or what might be the cause? Would leaving the wort to chill down 8 hours before boil have this effect? And most importantly, how will it affect my beer?

    The grist was some leftovers (but not old) from other brews, 53% pale ale, 22% wheat malt, 20% munich and a bit of crystal.
     
  2. Yooper

    Yooper Administrator
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    Something is wonky- it's just not possible to have a pH of 7 on wort with an mash pH of 5.4, especially post- boil. I don't know what happened, if it's not the pH meter though.
     
  3. okoncentrerad

    okoncentrerad Active Member

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    The pH 5.4 was the theoretical mash pH, according to the recipe builder. The actual reading was done the morning after (pH 7). I will go back and check the pH meter once more, to see if I've missed something in the early morning hours.
     
  4. Nosybear

    Nosybear Well-Known Member

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    That is weird - a mash of nothing but pilsner (the lightest and least acidic malt) in distilled water should come out at around 5.8. I'd start with the meter - if you can borrow one or otherwise cross-check it on reference solutions, check the meter. That it came out as a pH of 7 (neutral) is an indicator something is wrong - distilled water with no CO2 dissolved in it has a pH of 7 but not much else. But there is no way a wort should have that high of a pH.
     
  5. Mark Farrall

    Mark Farrall Well-Known Member

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    How long ago was the last calibration of the meter? Mine becomes dodgy after a week.
     
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  6. HighVoltageMan!

    HighVoltageMan! Well-Known Member

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    Absolutely, meters should be regularly calibrated. It's the only way to know if your readings are accurate. If your meter's probe is bad, about the only way you will know is to calibrate the meter. Slow response times are an indication the meter is losing a probe or the probe needs cleaning. A simple way to clean the probe is to soak the probe in full strength household bleach for 5 minutes and then straight strength white vinegar for 5 minutes. The better way is an acid based cleaner made for pH probes. After each cleaning the probes are soaked in pH storage solution for a couple of hours and then re-calibrated with 7.01 and then 4.01 solution. Probes need to be kept in a pH storage solution when not used. Drying out the probes often times destroys them and they need to be replaced. Most probes go bad on their own within 12-18 months.

    Single junction meters such as the Milwaukee PH-56 require more cleanings and calibration than a dual junction probe meter like the Milwaukee MW102.

    If it's not the meter then it's a weird bacteria that can raise the pH, most bacteria lower pH.
     
  7. okoncentrerad

    okoncentrerad Active Member

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    Thanks for the replies, yes it seems like it's the meter that's gone bad, have done some testing on it now. It won't calibrate properly either so I'm going to try cleaning it. Worst case I'll buy a replacement probe for it.
     

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