How to Know When Fermentation Has Finished

This blog provides information for educational purposes only. Read our complete summary for more info.

Outdated. New article here.
Portrait of Emmet Leahy

Emmet Leahy is the Chief Operating Officer and lead product developer at Clawhammer Supply, a small scale distillation and brewing equipment company. He loves the process of developing new equipment for making beer at home just as much as he does using it to brew his own beer. He's also passionate about teaching people how to use distillation equipment to produce distilled water, essential oils, and with the proper permits, fuel alcohol and distilled spirits.

Leave a comment

Please note, comments need to be approved before they are published.

96 Comments

  • S
    Comment Author: STeve

    I have a question that I hope you can help me with. I am a long time all grain Brewer and I am on my 2nd batch in my new still. Last batch my fermentation stopped at .02 OG was about .067, and I could not do anything to get it to move, so I figured I must not have achieved full conversion? Second time around I used and iodine test to validate my conversion then moved it to my conical. I hit it with a turbo yeast on Monday, now at Friday and it’s stopped at 1.025, Making me nervous… Not sure what the possible cause might be. Secondly, when I distilled my last batch I got decent yeild for quantity but a alcohol content of 40-55% about half the proof I expected ( I made all my cuts at specific temps). But I figured with the lower fermentation I would just get a lower yeild of high proof, not normal yeild with lower proof? Hopefully you can help me I am new to this so just a few questions.

  • M
    Comment Author: Mike

    Dear friends, i am a newbie, my fermentation is going on with 4KG sugar and 1KG molasses in 20l water. Used 20g of bakers yest hydrated in a slice of bread, with an air lock bucket. Its been 10 days and bubbling, how many days should i wait

  • P
    Comment Author: paul

    I’m running a 5 gallon still with a thumper before the coil , is the first few ounces coming off the coil still poison or has the thumper eaten that ?

  • S
    Comment Author: steve

    I’ve had this same thing happen to me before. What I did was get a packet of
    dry yeast – dissolve it in small amount of warm water with no sugar in glass
    when it has a good rise to it pour it slowly into your wash. It will start to
    eat the sugar again – let it set till done then run it as soon as it stops. your
    alcohol content should be good.

  • B
    Comment Author: Beau

    This question is for Jake (or anyone who knows). on the yeast, will the instant yeast still work? i unfortunately just ran across your post after i pitched flieshmann’s instant yeast. next time i’ll definitely use the active dry yeast, but i’m wondering if i should just throw this whole mash out now that i’ve pitched the instant yeast. 5 gallons of sugar wash, necessary nutrients/buffer, 10 grams of yeast.