Is there any reason why you can't use the same sample for all your gravity readings rather than taking a fresh sample each time? The idea being to take an initial reading and then keep this sample separate from the main brew and use this sample purely for gravity checks.

  • Is this sample going to have been pitched with yeast? Otherwise if kept sterile it won't change any.
    – brewchez
    Feb 11, 2014 at 20:04
  • yes it would be
    – robjmills
    Feb 12, 2014 at 10:20

1 Answer 1


I guess you're assuming the sample will continue to ferment with suspended yeast?

There's quite a few reasons why this can fail:

  • the sample may not be at the same temperature as the beer (both due to it's location plus it lacks the exothermic heat produced from the large volume of yeast in the main ferment.)

  • the sample may become contaminated and ferment with the help of contaminants (bacteria/wild yeast) resulting in a lower gravity than the main brew

  • the sample may not contain as much yeast as in the main brew, so ferments at a different rate

  • the sample may evaporate quicker (if uncovered and without an airlock)

  • Yeah, i'm assuming it would continue to ferment. The sample would be stored in the same location as the main brew and would be covered. That said, your arguments against it seem pretty solid - thanks!
    – robjmills
    Feb 8, 2014 at 11:10
  • You could use it as a rough guide. If it's at the same temp, and it ferments out, then you can be sure the main brew probably has fermented out too.
    – mdma
    Feb 8, 2014 at 13:48

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