Temp differential inside and outside of carboy?

Discussion in 'Homebrewing' started by hojo813, Oct 27, 2021.

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  1. hojo813

    hojo813 Initiate (0) Aug 3, 2018 Virginia

    I just watched a YouTube video and he mentioned that the temp in the carboy is about 4 degrees higher than if you have the temperature probe taped to the outside of a plastic carboy.

    Is this true? I thought it was maybe 1-2 but 4 is a lot! It can make or break a delicate beer. Mine is taped to the carboy and I cut a piece of a beer coozi for insulation. I'll definitely be doing an experiment as soon as I rack this pilsner to the keg and lager.
     
    #1 hojo813, Oct 27, 2021
  2. VikeMan

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

    There's no one-size-fits-all answer to this question. The difference between the temp in the middle of the fermenting beer and the temp measured by a probe taped to the outside would depend on several things.

    - size and configuration of the fermenter
    - the thermal mass of the beer, in part a function of its volume.
    - fermenter material and thickness
    - difference between ambient (room) temp and beer temp, which will not only vary by brewhouse and batch-to-batch, but also over the course of a single fermentation
    - type and thickness of the insulation covering the taped on probe
    - location of the taped on probe
    - probably more that I'm forgetting

    A very well known homebrewing guru has said that he taped a probe to the side of a fermenter and measured the internal temp and got the same answer, therefore it doesn't matter. Sometimes he doesn't put as much work into the advice he dispenses as he should.
     
    #2 VikeMan, Oct 27, 2021
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  3. hojo813

    hojo813 Initiate (0) Aug 3, 2018 Virginia

    I keep my car boy in a converted mini fridge that is precision controlled with a temperature controller and a reptile heater cord that I placed in a grill type pattern to heat the beer up. Only brought this up because I just finished the pilsner and that needs good temperature control and I was worried that it was ruined. Thanks
     
    #3 hojo813, Oct 27, 2021
  4. Supergenious

    Supergenious Maven (1,273) May 9, 2011 Michigan

    Type of yeast and how vigorous of a fermentation will make a difference too. As long as your max temp stays within a couple degrees of specified limit of your yeast, you’ll be fine. RDWHAHB.
     
    #4 Supergenious, Oct 28, 2021
  5. hojo813

    hojo813 Initiate (0) Aug 3, 2018 Virginia

    Oh yeah. I've found that out over the years.
     
    #5 hojo813, Oct 28, 2021
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