PH Meter and Hydrometer/Refractometer readings

Discussion in 'Homebrewing' started by drink1121, Apr 11, 2016.

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  1. drink1121

    drink1121 Initiate (0) Mar 23, 2009 California

    This is a Monday two-fer.
    1) just got a Milwaukee MW101 PH meter and have a question about reading it. I took a sample of my mash at around 50 C and adjusted the temp. on the meter to 50 C after calibrating it in the solutions. the readings, for several samples pulled, at about 30 minutes into the mash were about 5.3. just for science, I brought the same samples down to room temp. and measured, after adjusting the meter to 20 C, were around 5.45ph. anyone know what in the world is happening? is it not accurate at 50 C, even though the knob is adjusted accordingly?

    2) same brew day: I always use a refractometer to measure pre-boil and OG's. the OG on this was at 1.047. sine I had samples from doing ph readings, I decided to see what the hydrometer said and it read 1.022 at room temp. is the hydrometer just good for fermented wort? if not, what the heck is going on? (it has been consistently reading FG correctly according to calculations)
     
    #1 drink1121, Apr 11, 2016
  2. pittvkyle7

    pittvkyle7 Initiate (0) Apr 16, 2007 Connecticut

    I don't know about the ph meter, but you need the check the hydrometer in water - it should measure 1.000.
     
    #2 pittvkyle7, Apr 11, 2016
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  3. jbakajust1

    jbakajust1 Pooh-Bah (2,552) Aug 25, 2009 Oregon
    Pooh-Bah

    You will get a false reading when your wort is that hot with a hydrometer. Needs to be closer to 20C to get an accurate reading.
     
    #3 jbakajust1, Apr 12, 2016
  4. drink1121

    drink1121 Initiate (0) Mar 23, 2009 California

    yeah it was at room temp. - both hydrometer and refractometer were at room temp.

    also, my refractometer was calibrated with water beforehand***
     
    #4 drink1121, Apr 12, 2016
  5. VikeMan

    VikeMan Grand Pooh-Bah (3,067) Jul 12, 2009 Pennsylvania
    Pooh-Bah

    Was the mash finished when you took your samples for the pH readings? If not, you might not have had full extraction/conversion yet, so gravity would be low.
     
    #5 VikeMan, Apr 12, 2016
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  6. drink1121

    drink1121 Initiate (0) Mar 23, 2009 California

    it was not finished. do I need to wait until it is finished to take a reading? if so, how do I adjust the ph if its off? sorry, I am fairly new to ph adjustments, but not to all-grain.
     
    #6 drink1121, Apr 12, 2016
  7. VikeMan

    VikeMan Grand Pooh-Bah (3,067) Jul 12, 2009 Pennsylvania
    Pooh-Bah

    You take a sample for pH early in the mash. You take a sample for gravity (normally from the kettle) after the mash is done.
     
    #7 VikeMan, Apr 12, 2016
  8. drink1121

    drink1121 Initiate (0) Mar 23, 2009 California

    yeah I take the gravity then and I took the PH sample around 30 minutes into the mash. I should take maybe 5 minutes in going forward?
     
    #8 drink1121, Apr 12, 2016
  9. utahbeerdude

    utahbeerdude Maven (1,374) May 2, 2006 Utah

    Mash pH does decrease as the temperature increases, typically by about 0.2 to 0.3. In general, when people discuss mash pH they are talking about the pH of a sample that has been cooled to room temperature. Cheers!
     
    #9 utahbeerdude, Apr 12, 2016
  10. drink1121

    drink1121 Initiate (0) Mar 23, 2009 California

    right, but the Milwaukee I am suing has an adjustment for temperature. Should I just ignore this and cool to room temperature every time? if so, how do you cool quickly so I can still adjust the mash ph if necessary?
     
    #10 drink1121, Apr 12, 2016
  11. utahbeerdude

    utahbeerdude Maven (1,374) May 2, 2006 Utah

    The temperature correction on the meter makes it so the meter gives an accurate pH reading at the temperature of whatever solution you are measuring. It does not tell you what the pH would be if the solution happened to be at room temperature (RT).

    EDIT: Yes, cool to RT each time; use an ice bath if you want to do it quickly.
     
    #11 utahbeerdude, Apr 12, 2016
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  12. daem3384

    daem3384 Zealot (691) Nov 24, 2015 California

    I just want to reiterate that pH is a roughly linear function of temperature.

    pH @ rt= mash pH * 0.0055(mash T - room T) in Celsius.

    The temperature correction for the probe is for the computational software in the device, not for the above calculation, but this way you don't need to wait for a cooled sample.
     
    #12 daem3384, Apr 12, 2016
  13. drink1121

    drink1121 Initiate (0) Mar 23, 2009 California

    if I use this formula: 5.3*.0055(47)= 1.37. this doesnt seem correct. am I missing something?
     
    #13 drink1121, Apr 12, 2016
  14. daem3384

    daem3384 Zealot (691) Nov 24, 2015 California

    Oops, thanks for catching that. It's

    pH @ rt= mash pH + 0.0055(mash T - room T)

    This also has about a .05 uncertainty depending on the mineral content of your water, but is generally a good correlation.
     
    #14 daem3384, Apr 12, 2016
  15. daem3384

    daem3384 Zealot (691) Nov 24, 2015 California

    Also, are you sure that 47 degree delta T is right. Because if it is, that means that you're mashing at WAY too high of a temperature. There should be no reason for your mash to be 117F more than room temperature.
     
    #15 daem3384, Apr 12, 2016
  16. drink1121

    drink1121 Initiate (0) Mar 23, 2009 California

    154 degrees farenheit = 67.678 Celcius; 67.78-20(room temp) = 47.78.
    this equation makes more sense. my room temp. mash ph would be 5.54.

    edit* my actual room temp reading was closer to 5.45, but my mash was also 30 minutes in.
     
    #16 drink1121, Apr 12, 2016
    Last edited: Apr 12, 2016
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