Which temperature to use?

Discussion in 'General Brewing Discussions' started by jay3847, Jul 23, 2019.

  1. jay3847

    jay3847 Member

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    I just got a tilt and am learning new things about my setup: there is a significant difference between the temp at the top of the fermenter vs the bottom.

    In a 3 gallon carboy in the frig, I use an inkbird with a thermowell controlling a heat wrap giving me 70 degrees towards the bottom of the carboy (for example) and the tilt at the top reads 62. Everything is calibrated so I believe the numbers. It makes sense to me that the top of the wort would read colder in a glass carboy even though I've wrapped everything in a towel.

    I've read a number of posts saying this thermal difference is correct. So with that in mind, should I use the temp at the top of the carboy as my fermentation temp for an ale yeast, or the temp at the bottom?
     
  2. Mase

    Mase Well-Known Member

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    One way to fix this is to use a circulating fan to make sure the temps are the same throughout the chamber.

    During “active” fermentation, the temp at the top and the bottom of the vessel are pretty close as the active fermentation really mixes things around. If you ever watch an active fermentation through a glass carboy, you’ll know what I mean.
     
  3. jay3847

    jay3847 Member

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    I do know what you mean and that makes me suspicious about one of the thermometers. I'm not at high krausen yet, but close enough that the activity would have evened out the temp. Great point.
     
  4. jay3847

    jay3847 Member

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    And the answer to this was an Inkbird thermometer WAAAY out of calibration. That needs to be added to my pre-brew checklist.
     
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  5. Bubba Wade

    Bubba Wade Well-Known Member

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    I use an SS Brewtech fermenter with the heat exchanger coil and thermowell in the lid. Since I ferment in hot weather in my garage in Louisiana, the chiller runs frequently. My Tilt floats closer to the edge of the vessel and will often show a 2-3 degree difference with the controller. I don't worry about it much. There will always be some temperature stratification inside the fermenter as there is no active circulation and all mixing relies on natural convection.
     
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  6. Group W

    Group W Well-Known Member

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    Good points from Mase and Bubba. Couple more thoughts. Take 6 different thermometers and you will get 6 different readings, regardless of calibration. Temps are always swinging due to overshoot on heating and cooling targets on our systems. You can see it on your Tilt graph. +\- 2 degrees f is good by me. Jay, keep in mind that 3 gallons is not much thermal mass and temp swings will be greater compared to fermenting 5, 10, + gal. It’s a dynamic environment and we rationalize with static measurements. The proof is in the pudding. If it makes good beer, don’t sweat the small stuff.
     
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  7. Ward Chillington

    Ward Chillington Well-Known Member

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    And this begs the question, how did you or do you calibrate your stuff and what do you use as the benchmark or standard?

    Everything that I have found is that your "ice water bath" is supposed to be 32° F and a rolling boil at the center of a pot is supposed to be 212° F and the only device I have that seems to get that right is my old mercury thermometer. So when you are stressing about that two or that half a degree it's time to recall the sage wisdom of Palmer and Papazian....."it's a robust system" and "Relax, don't worry, have a homebrew".
     
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  8. Head First

    Head First Well-Known Member

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    I use a regular lab thermometer to check kettle dials. They vary by a few degrees so I get mashed in correctly and just use whatever temp the dial says as it gets recirculated.
    1 or 2 degrees for sample temps is close enough so use little pocket digital for them. And the stick on one's work well for ferm and lagering temps. No need to sweat 1 or 2 degrees IMO. Actually the stick on one's are very acurate.
     
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  9. Hogarthe

    Hogarthe Well-Known Member

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    For super accuracy the freezing water/boiling water isn't supposed to be good enough. You want to calibrate at the temps you actually use. But that's way harder to do accurately because how do you know if something is 150f or 68f without a calibrated thermometer? It's close enough to calibrate at 32 and 212, but keep in mind altitude can change your boiling point.
     
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  10. Ward Chillington

    Ward Chillington Well-Known Member

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    Right like 1 degree F per 500' above sea level or .5 C for you 152M guys.
     
  11. Nosybear

    Nosybear Well-Known Member

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    It's 200 degrees here at 6,000 feet. I have to adjust hops to compensate.
     
  12. Hawkbox

    Hawkbox Well-Known Member

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    97.8C here.
     
  13. Nosybear

    Nosybear Well-Known Member

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    Squirrel! Mine translates to 93.3 C.
     
  14. Hawkbox

    Hawkbox Well-Known Member

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    Can't even brew a good cup of tea that low.
     
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  15. Bubba Wade

    Bubba Wade Well-Known Member

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    99.93 °C here in Louisiana. I don't believe that I need to compensate.
     
  16. Ozarks Mountain Brew

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    I'm at 1,299 ft and wort boils at 209 F here
     
  17. Ozarks Mountain Brew

    Staff Member

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  18. Bubba Wade

    Bubba Wade Well-Known Member

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    Note that the boiling point of wort will be approximately 0.4 C (0.7 °F) above the boiling point of water for a given elevation, assuming a 1.050 specific gravity.
     
  19. Trialben

    Trialben Well-Known Member

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    Yep now hes quoting from other threads on this site.
     
  20. Hawkbox

    Hawkbox Well-Known Member

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    I mean I do that occasionally, but usually because I'm drunk.
     
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