How do you measure mash temp reliably?

Discussion in 'General Home Brew Equipment Discussion' started by Multigrain, Oct 4, 2019.

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  1. Oct 4, 2019 #1

    Multigrain

    Multigrain

    Multigrain

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    Hello!

    Never thought the day would come where I would ask this. But as I have had problem to get FG down to where I want it lately I thought it would be interesting to hear how you get a reliable result?
    I have done about 65 all grain batches by now and thought I would had nailed it by now, but nope!

    Through my wife who work at a lab I had borrowed a calibrated highly accurate thermometer (0.00 precision). Its digital and read the temperature immediately.
    When I dip it in various places and depth in the pot it can differ up to 5C at a bad day. It does level out after stirring the pot around for a while and left to rest for about 10 min, but even then it can vary a bit. Do you trust your reading and how do you do? (My last Munich Dunkel came into FG 1.016 instead of 1.011..:( and i dont know why. High FG has been a problem lately.

    Rant start here:
    What i have found is that it is really difficult determine the accuracy of the measurement of thermometers in beer brewing! I would not reliably be able to tell the differentiated closer than 1.5C at the most based on an average in the pot. If there is interest I can try to record the variation next time and make it to a web friendly gif or something.
     
  2. Oct 4, 2019 #2

    Rodcx500z

    Rodcx500z

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    Hi I understand your question but I don't think I know the answer all I can say is what I do, I heat my mash water say to 70c turn the kettle off and dough in then take a reading I have a proper food grade industrial probe, If the mash is were I want it I stick the lid on and leave it, every 15 mins I give it a stir and check temp if it's got to low I turn the heat on lowest setting 900w for 5 mins stir and take a reading then heat off, I do this 3 times over the hour, if you turn the heat on make sure you stir to get an even temp through the mash, I hope this helps with your problem even if only a little acheers.
     
  3. Oct 4, 2019 #3

    cushyno

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    No matter what I measure with, PT100 probe attatched to a PID, or Inkbird handlheld probe, I always double check with a trusty 18 yr old glass thermometer.

    Stir the Mash, let it settle. You're bound to get hot spots and temperature gradients across the mash, unless you circulate.
     
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  4. Oct 4, 2019 #4

    Rodcx500z

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    +1 on hot and cold spots, I can set mash temp on the kettle and it works but the probe is at the bottom, so temp is to hot down there and cools in the middle and top so I just do the best I can acheers.
     
  5. Oct 4, 2019 #5

    Ghillie

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    To even out mash temperatures properly, you really need to be recirculating.

    If high FG is a problem, I would mash lower: in order to compensate for your innate errors with consistent temperatures throughout the grain bed. ie your temperature readings are lower than they actually are.

    FYI, you should still be getting 1.010 or lower, even with a 67C mash, so your temp readings must be way out.
     
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  6. Oct 5, 2019 #6

    Brew_DD2

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    I would also be looking at fermentation with those FGs. Do you ramp up temps at the end of fermentation to complete attenuation?
     
  7. Oct 5, 2019 #7

    Alside101

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    Check your hydrometer. Mines out by a few points so it looks like its high but its not
     
  8. Oct 5, 2019 #8

    Clint

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    Wiv me elbow...
    I mash in around 80 and take a reading...it's usually not far away. I make any adjustments as required measuring as I go with my Inkbird BBQ thermometer.
     
  9. Oct 19, 2019 #9

    Multigrain

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    I missed I got so many replies, sorry guys, and thank you!
    One think I have not been doing is ramping up the temp. I usually set it to 18-20C and keep it like that for usually 14 days then I bottle.
    I have a glass thermometer I bought from the brew shop and another regular kitchen therm. I will check all of them in boiling and ice water to try and find ny offsets.

    It was many batches ago I mashed higher than 65C so I am surprised as my experience of fermentability has been much lower than expected. Will make a wit tomorrow, lets see how that goes. Will also check my hydrometer and compare it to my refractometer I use during brew day.
     
  10. Oct 19, 2019 #10

    BeerCat

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    I will second that. I mash at 67c sometimes and still get to 1010. Recirculating will even out mash temp.
     
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  11. Oct 20, 2019 #11

    matt76

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    Several things here:

    Calibrate your thermometer - I'm a geeky scientist/engineer type so before I ever did my first AG brew I calibrated my thermometer by sticking it first into a boiling kettle of water and then into some melting ice.

    Mash tun - I actually mash in my brew kettle in the oven (it just fits) where I can control the temperature. Now I used to just add the grain and then hot water, stirring as I go (no grain bag!). Like this I could fit my mash temp bang on every time.

    However, now I clip 2 grain bags (one fine mesh, the other coarse) to the rim of the kettle, add my grain, then the water and stir. I'm struggling now to got my mash temps - my theory is some of the water goes through the grain bags and isn't mixing so well with the grain. But I definitely notice warmer and colder spots as I stir.

    Hydrometer error - I've checked mine numerous times in tap water, water from the softener and also de-ionised water, and checked the temp is 20degC. Every time it reads 1.003-1.004 without fail. This is an issue when trying to read FG. For example if Brewer's Friend predicts FG 1.013 but the hydrometer reads 1.016 - well, is it really done or does it need a few more days.....
     

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