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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).

  • fermenting after the first 24 hours (bubbling like crazy). can I stir it gentle once, then cover it back up and leave it?
    Will it harm the fermentation process?

    Posted by Dwayne Patlyek on August 23, 2018
  • Just looking through and it looks like,theirs a lot of people interested in this art . That’s great, Enjoy .

    Posted by Gregory Nodine on July 31, 2018
  • I made one of those cocktail type moonshine every into. And I put into the jar warm and sealed even with my alcohol is used. Is that okay? I made it for a couple parties we’re going to be going within the next week’s.

    Can I make those cocktail brews and seal them warm like that will they keep for any length of time? What is your subsections? I’ve got several different recipes I’d like to try. And I’d like to make and store. Do I let them cool completely before I put the lid on?

    Posted by Cheryl on June 18, 2018
  • ok, tHIS is how II make a mash. Add 1 part corn meal to 3 parts hot water (3 to1 ratio). Stir until it’s like a super thick glob of starch. Cook out for about 1/2 hour. Sprinkle amalyse enzyme to mash & stir until like a thin soup & cook for about 1 hour at 70C (converting the starch to sugar). Let cool to about 38C. Add mash to container with heated sugar water (2kg sugar to 4 litres water), activated yeast stirred through. Leave sit for about 2 weeks. strain well before stilling. .

    Posted by Dave on June 05, 2018
  • do i leave the corn goodies in the wash to fermet or does it have to be taking out

    Posted by josie on May 16, 2018
  • If the mash to make bourbon cooked long the 4 hours what happen the Mash

    Posted by Sal on April 09, 2018
  • has anybody heard of ti root and sugar cane moonshine

    Posted by ken on April 01, 2018
  • 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


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