I started a fermentation 24 hours ago and it has increased the temperature from 22°C to 28°C in the last 8 hours. Additionally the gravity dropped from 1.060 to 1.024 already which seems insanely fast for a brew that is supposed to end at 1.017.

I'm using a Fermzilla with pressure kit and put the insulation jacket on immediately, I guess that's where the temperature rise came from?

Is this gravity drop normal? It seems insanely fast to me.

  • Very fast, but expected given the temperature keep your airlock clean and hopefully you like your beers a little fruity.
    – mreff555
    Jun 21, 2020 at 1:47
  • Fermzilla is closed fermentation, so no airlock! But yes, pretty fruity 😅
    – sebastiaan
    Jul 3, 2020 at 8:37

1 Answer 1


It is very fast, probably due to the high temperature (the higher the faster it will ferment), the insulation jacket would keep it warmer. The type of yeast used cans also cause this, some yeast are more vigorous than others, but in the end, the main reason is the temperature.

Depending on your room temperature, you might not need an insulation jacket (I never used one).

  • I only got the jacket to keep sun out and thought it would maintain the temperature but of course the reactions going on inside the vessel produce heat, which I failed to anticipate! Fermentation was completely finished in 36 hours, oops. Beer tastes quite good though.
    – sebastiaan
    Jul 3, 2020 at 8:39
  • 1
    To block light, I sometimes put a t-shirt over my carboys. No need to have something insulated in this case.
    – Philippe
    Jul 3, 2020 at 13:34

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