First time home brew. I followed instructions and pitched yeast into wort (which looked like mud) airated it a bit, placed in my basement with a cover over it.

There was a bit of activity in the first 3 days, a tiny bit of clarity, but it would appear like the yeast has stopped? No activity or movement in the carboy. The vapour lock isnt bubbly or anything. There is an inch of setiment at the bottom of the carboy.

Question is... since it was only active for 3 days, should i do something like pitch more yeast? Shake it? Or is it done fermentation? How do brewers know? Thanks!

  • 3
    'How do brewers know?' Best way is to sample the specific gravity, usually with a hydrometer. When it stops changing, the yeast is done. Mar 2, 2016 at 12:59

2 Answers 2


As Fraklin commented, the best way to know is by measuring the specific gravity. This will tell you how much sugar is in the wort/beer, both before and after fermentation. When you are getting stable gravity readings over a couple/three days, then you the yeast is done. If the gravity is still "too high", then you know the yeast have stalled out, or the wort is particularly un-fermentable.

A 3-day fermentation is not unheard of, especially for moderate gravity ales fermented warm.


Agreeing with Franklin. Taking the specific gravity readings over 2-3 days is the best practice. You could also pick up a refractometer to take gravity readings if you need to. I use one since I do 1-2 gallon batches frequently and only larger batches when I know the recipe is good. EDIT: As a note from a commenter, refractometers do not give direct readings in the presence of alcohol; you'll need at least a correction.

However, just because there isn't any more alcohol being produced or visible activity doesn't mean 'fermentation' is completely done. Fermentation isn't just about making alcohol. I assume you've heard of some of the byproducts that yeast make while eating, pooping, and reproducing. Some of them are not good BUT yeast love to take care of themselves so after the alcohol is made they will also clean up some of those nasty byproducts, cleaning up the flavor of the beer.

My novice suggestion would be to raise the ambient temperature of the fermentation chamber or just wrap it in a sweater or blanket. Three days is usually when the frequent activity stops for a lot of my brews as well but I always let them sit at the least a week. It can't hurt!


  • Just a note that refractometers do not give direct readings in the presence of alcohol; you'll need at least a correction. I use a refractometer pre-fermentation, and a hydrometer post, as do I think most people who use refractometers.
    – jsled
    Mar 2, 2016 at 17:21
  • Ah yes, you are correct @jsled. There are a number of calculators and apps out there that you can use if you do wish to use the refractometer to determine your final ABV. I generally just use the refractometer to ensure fermentation has stopped and if my batch is bigger than 2 gallons I just use a hydrometer to snag that actual OG and FG.
    – Dan Hutt
    Mar 2, 2016 at 19:55

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