May 15, 2020

Stuck Fermentation


You’ve spent hours making your latest creation. You’ve sweated over the mash tun, rested at all the notable temperatures, infused, decocted, whirlpooled, first wort-hopped, hop rocketed, chilled, and pitched your yeast. You relax and pour yourself a pint, looking forward to seeing that layer of krausen the next day and hearing the happy sound of healthy yeast pushing off C02. Now, you get to choose your own adventure.

We’ll start with adventure scenario number one. You walk into the room and absolutely nothing has happened - no bubbles, no airlock activity, no action whatsoever. You decide to give it some more time, as you’ve heard that sometimes it takes a while for the yeast to get moving. Another day passes, and you still don’t see anything. Don’t fear! All is not lost. There are a few easy things you can do to figure out what’s happening and get your batch back on track.

How To Start A Completely Stuck Fermentation

  1. Check your gravity! If your fermenter isn’t properly sealed (a common occurrence with buckets) you could have a big crop of healthy yeast working away invisibly.
  2. If your gravity has dropped, or if you see a thick foam on top of the beer or signs of that on the sides of the bucket, seal up your fermenter and leave it for a few more days. You have plenty of cells, and nothing to worry about.
  3. Check to see how warm your fermenter is. If it’s sitting on your cold basement floor, it might be too chilly for the strain of yeast you’re using. Check the manufacturer's recommendations for that particular strain. Warming it up a couple of degrees could make a world of difference. You can do this by using a temperature controller and heat wrap, or for very minor changes put a blanket under it to insulate it.
  4. If your gravity hasn’t changed, put in more yeast! If it’s a bigger beer (anything over 1.070 OG) it’s worth it to delay a little longer and get a starter going. Otherwise, pitch the appropriate amount of yeast for your gravity. In this circumstance, you can also re-aerate the wort before you put the yeast in. Shake your fermenter for 5 minutes, or use your oxygenation kit as usual. Oxidation won’t be a concern until after the fermentation is underway.

Now, let’s move onto adventure scenario number two. You have a fermentation for a few days, but it’s a bit sluggish, and it stalls out early. You check your gravity, and you’ve dropped, but not nearly enough. A day later, nothing has changed.

How To Fix A Sluggish Fermentation

  1. Don’t Re-aerate at this point. You could oxidize the beer in the fermentor.
  2. Take the time to make a yeast starter. Because the yeast that was present has scavenged all the available oxygen to multiply and go forth, you need a yeast culture that’s at the pinnacle of health and activity. You get this by making a starter and pitching it at “high krausen” or the peak of froth and activity.
  3. As far as which yeast to pick, you aren’t limited to the same strain you used initially. If you had a significant enough drop in gravity, you will already have gained the yeast character you’re looking for. This is generally produced in the first 48 hours of fermentation. My two favorite picks for a stuck fermentation are Wyeast 3711 and Safale US-05. Both are clean, high-attenuating, yeasts that can survive in higher alcohol, nutrient-scarce environments.
  4. Speaking of nutrients, add a small dose of yeast energizer. The yeast that stalled-out are the vast majority of nutrients in there, so a little extra will go a long way. Don’t go over the manufacturer recommendations of ¼ tsp. per gallon, as that can cause problems as well.
  5. If you can, once your batch is at terminal gravity, warm the fermentor up by a couple of degrees and let it sit for another 24-48 hours. The first crop of yeast put off some odd chemicals when it got stressed out, so warming it up will give the new yeast a chance to re-absorb those. Check out our controlling fermentation temperature article.

And there you have it! Beer is a remarkably resilient thing, so don’t panic! A little TLC, and your batch will be right back on track again.

Read More About Fermentation:

Fermentation - Learn about fermentation for beer. 

Cold Crashing - So what is brewing yeast anyway?

Controlling Fermentation Temperature - Make sure your yeast is happy with the temperature. 

How To Ferment For Higher Gravity -  If you’re making a high ABV beer, read this.