Is there any reason not to simply lower a hydrometer into my carboy during secondary fermentation, so that I can monitor gravity just by peeking in with a flashlight?

I'm thinking about doing this with a recent tripel batch, so I don't have to disturb it multiple times by taking readings. I'll take precautions like sterilizing the hydrometer. I also think I will tie something like dental floss (sterilized) to it so that I can gently lower it in, drape the loose end over the lip wedged between the lip and the bung, and remove it safely later.

It'll sit there like an iceberg poking its head out, and I can act early if I start to feel like fermentation has stuck. Keep in mind this a beer I would like to leave in the secondary for 3-6 months.

This seems like a good idea to me, but I have lots of "good" ideas that turn out bad. Is there any reason you would not do something like this (either from experience or imagination)?


3 Answers 3


Since this is secondary your gravity shouldn't be changing much. Unless you're moving to secondary during active fermentation, your beer should be at final gravity when you move it.

Unless you're adding fermentables to your secondary, I can't think of a reason to track gravity. And if you are adding fermentables, then you might have some kreusen. And that kreusen would stick to the hydrometer and throw it out of calibration, giving you faulty readings.

So, you could do this, but I'm not sure what it gets you.

  • 1
    100% agree. There will be nothing but maybe a couple points change in secondary.
    – brewchez
    Commented May 8, 2012 at 22:36

The krausen is going to get all over it and potentially make the scale difficult to read if it cakes up in the wrong spot. The churning from active fermentation could also complicate reading a measurement.

  • Right, but that's why I'd be doing this in the secondary. My secondaries usually start with only a thin (1mm?) layer of bubbles and then become placid. Even if the bubbles are actually krausen foam, what about waiting until the surface is placid? Commented May 8, 2012 at 18:04
  • 1
    But why do you need a hydrometer reading every time you look at it? Leave it there for the months you're talking about and then check it.
    – Denny Conn
    Commented May 8, 2012 at 18:41
  • the question is about secondary - no krausen nor churning.
    – mdma
    Commented May 8, 2012 at 18:45
  • By definition gravity should be stable in secondary. Otherwise it isn't a secondary.
    – bk0
    Commented May 8, 2012 at 20:08

Here's the trick:

Get yourself a plastic beer/wine thief and sanitize it along with your hydrometer. Do the thief motion by moving it up and down to fill the reservoir and drop the hydrometer right down in there. You'll get nice clean beer from the bottom and don't need to worry about losing the hydrometer. When finished, just touch the end of the thief on the side of your fermenter and the beer will drain right back in.

I bought mine from the local homebrew store and made sure it was large enough to fit standard hydrometers. Like this one:


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