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January 29, 2014

Making Moonshine - How to know when fermentation is finished: Part 1

So you have 5 gallons of delicious corn mash fermenting in your basement and your Clawhammer moonshine still has been assembled and cleaned. You already read our article Bourbon, Whiskey, Vodka and Moonshine - How Much Yeast? and you added the correct amount of healthy yeast. Now you need to know how to tell when it's done fermenting.

Fermentation Variables

There are a few variables that can impact how long fermentation will take.

  1. 6.5 gallon glass carboy with corn whiskey mashThe type of yeast you use will play a large role in the amount of time it takes for a mash to ferment. Turbo yeasts will finish fermenting a lot faster than a bread yeast will.

  2. The temperature of the room the mash is fermented at will have a big impact on how long it takes to finish. A mash fermenting at 80 degrees will ferment a lot quicker than a mash fermenting at 55 degrees. 

  3. The amount of sugar is the mash will also play a big role in the amount of time needed for fermentation to finish. The more sugar in the mash the longer the fermentation will take. If you have an 8% ABV mash it is going to ferment a lot quicker than a 20% ABV mash. 

Measuring Fermentation - the Easy Way

We like to call this the "set it and forget it" method. It applies if you have your mash fermenting in a carboy or a bucket with an airlock.

Make sure 18-48 hours after you add the yeast to the carboy/bucket that you see movement in the airlock. You should see the airlock bubble a few times a minute. If you see activity in the airlock it means that the yeast is working and you're good to go. Let the mash sit for 14 days. If you still see bubbles in the airlock after 14 days let it sit for another few days, or at least until you see no bubbling for at least a minute or two. Once there is no activity in the airlock, the mash is ready to run. This is a non scientific method but has been  pretty reliable in terms of judging when fermentation has finished.

What if I don't see any activity in air lock after 18-24 hours?

If you don't see any activity after 18-24 hours make sure that the lid and airlock are tight. If both are tight then gently swirl the bucket/carboy- you just want to mix everything together. Check back after 12 hours if you still don't see any activity then add more yeast from a new yeast starter. After you add more yeast check back after 18-48 hours and you should hopefully see some activity. You should also try and keep the bread yeast happy -they seem to thrive between 74-78 degrees.

Monitoring Fermentation - the Scientific Way

The most accurate way to monitor the fermentation process when making moonshine is to use a hydrometer. Taking specific gravity measurements with a hydrometer not only lets you know that it has completely finished fermentation, it also allows you to determine the potential alcohol of your mash and the actual alcohol content of the wash. These numbers can be used for all sorts of things and we discuss all of this in our article on monitoring fermentation (the scientific way).

  • Can i put a glass carboy in a large aluminum bucket of water and heat the two together to vaporize? in other words, indirectly heat the carboy and use it as a still?

    Posted by Harry on January 16, 2018
  • At what temp should wheat mesh maintain until finished and what is the best yeast to used for wheat vodka

    Posted by DEnny sEnters on December 28, 2017
  • Man some of you guys need to do research on moonshine b4 you do a ferment. No Dnt add turbo yeast to an already fermenting bucket. You Dnt have to siphon water off there is no way for you to do that. That’s why you distill it. Nobody ever taught me anything. I watched moonshiners and did plenty of research and I’ve never had a problem. I have a 5 gallon going now with Fleishman yeast for 6 days at around 75 degree room it bubbles 1 time every 2 minutes. I’m gonna let it set another week

    Posted by Bill on December 17, 2017
  • Man some of you guys need to do research on moonshine b4 you do a ferment. No Dnt add turbo yeast to an already fermenting bucket. You Dnt have to siphon water off there is no way for you to do that. That’s why you distill it. Nobody ever taught me anything. I watched moonshiners and did plenty of research and I’ve never had a problem. I have a 5 gallon going now with Fleishman yeast for 6 days at around 75 degree room it bubbles 1 time every 2 minutes. I’m gonna let it set another week

    Posted by Bill on December 17, 2017
  • You guys are way overthinking this entire process. All you need is for yeasts to eat the sugar and turn it into alcohol. Then you boil off the alcohol at a temperature lower than which water boils (212) for those that don’t know that. Henceforth you get distilate that is always above 50% alcohol. Once your run starts to slow down even while still at 210 degrees you better start paying attention to the liquor coming out of your worm, it will get cloudy very soon thereafter. If its me, once it only drips at 210 degrees i shut er down and pour whatever else is left in the still out.

    Posted by SHine RHine on October 25, 2017
  • How long can fermentation sit after bubbles stop?? Is 2 or 3 days ok ??

    Posted by Stumpy Al on October 09, 2017
  • After fermentation do I need to let the mash set a few days before running it?

    Posted by LEwis on September 08, 2017
  • It states in this in this article pretty clearly that 1-2 minute spacing between bubbles in the airlock means it’s done, especially if it’s been fermenting for 14 days already. This is also not a place to ask questions, but to make comments.

    Posted by Joseph on September 07, 2017
  • Hi. I have a 5 gallon bucket of mash working, and I’m getting bubbles through air lock every 1.5 -2 minutes. How much time do I have before I have to run it before I’ve waited too long?

    Posted by Vince on September 05, 2017
  • I am on my second run. My first run didn’t turn out so hot as we were brewing up that batch every drop came out cloudy or had a taste of water with no alcohol content at all. We think we jumped the gun but our yeast wasn’t fizzing or bubbling as you said in this post still came out as water. Now this next batch we are running would it have a natural smell as to when the yeast is done with fermentation?

    Posted by John on September 05, 2017
  • Where I live the summer temperatures are also too hot for the turbo yeasts. some solutions are:
    - cool your wash right down to 18 degrees celsius before adding the yeast;
    - Put the fermentation bucket in another bucket with water- evaporation helps cooling down a little;
    - use distillers yeast that may generate less heat on its own.
    Overheating of the wash during fermentation will result in less of an alcohol yield, but the end result may still be impressive.
    I don’t know if it gets cold in your part of australia, but turbo yeast gives impressive results (up to 22%) when the fermentation bucket is kept really cold.

    Posted by Abe on June 20, 2017
  • I have had my mash working for a week with turbo yeast and its almost quit working and its kinda week can i still run it

    Posted by Jimmy Wilson on February 24, 2017
  • I am new to this and may sound like a stupid question but here it goes.
    Can i add turbo yeast to my already fermenting mash ? If so should i add the 24 or 48 hr yeast. i didnt plan very well and going on vacation .
    As of today it has been 3 full days of fermentation .
    Please help !!!
    Thanks in advance

    Posted by Jon on February 21, 2017
  • A quick question. At the end of fermentation do I need to siphon off the water or do I leave for the processing? I have a flat top still and the bottom is the fermentation pot. Any help will be appreciated.

    Posted by Bill on February 20, 2017
  • Have my corn maize & sugar w/whiskey turbo yeast in 6.5 gal bucket,do I wait until all bubbling has stopped or is there a day limit (like 2 weeks)

    Posted by MIke cHristensen on February 03, 2017
  • ottawa canada

    im did a double batch of the rebel rum recipe from this website, (with a few secret adds), and pitched it with 1 pack per carboy Lavlin ec 1118 yeast – its been bubbling for 21 days straight, in a 70 celcius room. first 14 days it bubbled 21 times per minutes, then slowed to half that. if you raise the temp in the room to 5-10 degrees it will speed up the process – but the yeast i used was 18%abv which is also high so its taking longer than normal. as longs as its bubbling…let it bubble…until it stops. like the joe dirt movie, “He’ll finish when he’s done dear”.

    Posted by jason on January 27, 2017
  • Gday guys I live in Perth Western Australia and the temperturehere in summer is on average 37 degrees cellcus I just did my first ever mash a simple sugar shine using turbo yeast (it was recomended to me by the brew shop) I pitch the yeast at 30 degrees but today’s temp has been 39 degrees I have managed to keep the mashes temp down too 34 degrees will this result in a bad was

    Posted by John mastaglia on January 05, 2017
  • My mix is in a 5gal water cooler.I place 4 to 6 inches of whole corn,10 lbs of sugar and 6 pks of yeast.Fill container with water.mix well and allow to seat for 30 to 40 days.At that time there is no more activity.The final product produces 1 quart and a 5th of good moonshine.The proof is always a 100 proof.

    Posted by Pat Leary on December 07, 2016
  • I am new to the whole home brewing community. being this is my first time to do a run, I am making 2 different 1 gallon batches. I used the same amount of pre distilled water, bread yeast, and sugar in both. the difference is one has strawberrys and pineapple the other is just sugar. my concern is the one with fruit has stopped as far as any activity (in the airlock, or any small foaming/bubbling) and the sugar one is still going strong {bubble the airlock once every 3 seconds or so}. at this point they have both been going now for 4 days. any advice or insight would be greatly appreciated.

    Posted by justin on October 13, 2016
  • Is it necessary to use thump keg

    Posted by Popav on August 07, 2016

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