When to stop fermentation - How to stop fermentation

Discussion in 'General Brewing Discussions' started by AHarper, Jul 28, 2020.

  1. AHarper

    AHarper Well-Known Member

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    OK the recipe says OG = 1.048 and FG 1.010 but the gravity hasn't been at 1.010 for 3 successive readings. Do you stop it now - and hit the spec - or do you just let it progress until the yeast does it's work and you shoot past the target FG?
    How would you stop it anyway? Just rack it off the yeast? Is there any other way? - Asking for a friend lol.

    It has always puzzled me as to how you can (accurately) determine the FG - there are so many variables that we amateurs can not control as well as the big guys. Does it matter? Who cares as long as it tastes good - except that it's twice the strength you expected. Hic.
     
  2. Hawkbox

    Hawkbox Well-Known Member

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    Largely depends on what you're doing with the beer.

    If you are bottling, best to leave it until you hit the same reading 3 days in a row. FG is purely a theoretical math calculation so don't bet the farm on hitting it. The main risk here is overpressuring the bottles if it isn't done fermenting.

    If you're kegging, try to wait until it's done but if you're bored go ahead and keg it.

    As you say, we're all really amateurs doing the best we can.
     
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  3. Vallka

    Vallka Well-Known Member

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    Let it Ride
     
  4. Blackmuse

    Blackmuse Well-Known Member

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    This is very true... However, if you brew a recipe enough times and are patient to see when it finishes each time, then you can get a good feel for it. The same can be said with yeast... Use one yeast enough times and you can get to know, based on experience, when it is finished. (at least this is what I have found)

    I have a few recipes that I have brewed enough times that once I hit that FG I feel safe kegging/bottling.

    Right now I have an Oktoberfest that I am unsure about as I have never brewed it before, I used a different step mash, and it is high on the FG. However, I am very familiar with the yeast and it has been long enough and appears to be done. I have doubts that it will continue to drop in points but I will be patient and wait it out just because there are too many variables against me.

    In your case - @Hawkbox gave some solid advice.

    Time certainly never hurts. :) (unless you count our curiosity)
     
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  5. Bubba Wade

    Bubba Wade Well-Known Member

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    I have seen some fermentations go 5 points past target and turn out fine. I usually let it hit a steady reading and give it another 4-5 days. There are still some fermentation activities going on even after the FG hits target.
     
  6. Craigerrr

    Craigerrr Well-Known Member

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    Why are you anxious to package it?
    How long ago did you pitch the yeast?
    Best advice is to let it ride until you know it is done, especially if you are bottling.
     
  7. AHarper

    AHarper Well-Known Member

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    just a general question Craig but one I have though of many times
     
  8. Craigerrr

    Craigerrr Well-Known Member

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    Fair enough sir, but the yeast are living organisms, they consume fermentable sugars, and produce alcohol, Co2, and heat in the process. Kind of like your stomach digesting food, how do you stop it from doing that, you just don't. It is largely out of our control.
     
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  9. J A

    J A Well-Known Member

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    FG is just an estimate until the beer finishes fermenting. When it's definitely done, verified by 2-3 days of steady readings, that's your FG. If it's a couple of points lower than expected, that's fine and will almost make the beer better, not worse. We get pretty used to hitting close but it's not unusual for a point or two variation, even when we've brewed the same recipe over and over.
     
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  10. AHarper

    AHarper Well-Known Member

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    My stomach is not out of control....has my wife been speaking to you? lol
    upload_2020-7-29_10-52-38.png
     
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  11. ^Tony^

    ^Tony^ Active Member

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    #11 ^Tony^, Jul 29, 2020
    Last edited: Jul 29, 2020
    I have found brewing is an "almost" science. You have/build a recipe but the actual brew day is hardly ever perfect. I used to get hung up on the numbers. Now I focus on theory, process, and most of all safety. If I am within a few points on OG/FG/SRM/BTU etc, I'm happy.

    As a rule of thumb I'd say don't panic if you miss the numbers or it takes a few extra days to ferment or if the fermentation is slow to start or the color is a little off or its not dropped as clear as you want. About the only 2 things I think are a MUST is sanitation and making sure your ferment is done before you bottle to avoid bottle bombs (either by measure with a hydrometer or by waiting a few extra days/weeks). Everything else is flexible.

    As more than a few have said, FG is just a recommendation or a kind of "heads up! fermentation might be close to finishing" kind of thing. Fermentation never really stops the yeast go dormant. FG a little low or a little high is fine as long as the numbers stop changing for at least 3 days, which indicates the yeast have gone dormant because they are out of sugar food. Then think about bottling.

    You beer will turn out well (or at least drinkable for you) 99.5% of the time even if you miss your numbers or your timing schedule it extended.

    Technically, I would think you can keep a fermentation going indefinitely, or until the high ABV makes the beer toxic to the yeast, by continuously adding sugar for the yeast to process. Unless you re-boil your beer (yucko_O) ...that will kill the yeast completely but then you can't bottle condition because there are no yeast to do it.
     
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  12. Daniel Parshley

    Daniel Parshley Active Member

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    I use the taste test to determine when to bottle (anyone else do this?), in addition to BRIX being the same for several days. I have noticed that the BRIX rises a few points at the end. If you are using a clear fermenter vessel, you will see it clear as the yeast finishes up and drops out of solution.
     

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