Have you ever been frustrated with a stuck fermentation? It’s one of the most common issues home brewers face when making beer.

If fermentation does not start or stalls, the result can be an overly sweet and unbalanced beer. Fortunately, diagnosing the problem is easy as taking steps to get your beer fermenting again.

Fermentation is one of the most critical steps in the homebrewing process. But what happens when fermentation stops before it should?

This can happen for various reasons, and there are several solutions to fixing a stuck fermentation. Let’s look at what causes a stuck fermentation, how to diagnose it, and how to fix it. 

What Causes Stuck Fermentation? 

Several possible explanations exist for why your stuck-fermentation beer may have stalled out. One possibility is that your yeast cells did not have enough oxygen when pitched into your brew.

Yeast strain needs oxygen to multiply and convert sugars into alcohol, so fermentation will slow down or even stop entirely if there’s insufficient oxygen.

Sometimes putting the same strain of yeast back in suspension will get it going again. Add some yeast energizer to the beer.

Another possibility is that your wort was too hot when you pitched the yeast, which can cause them to become stressed and die off before they’ve had a chance to do their job.

Finally, high levels of bacteria may present in your wort, preventing the yeast from doing its job. 

The most common reason for fermentation to be “stuck” or appear to have stopped is temperature fluctuations.

If the temperature of your beer is too high or too low, this can cause the active yeast cells to become dormant, thus halting the fermentation process.

Additionally, if you don’t use enough more yeast or if your wort has an unbalanced pH level, this can also cause your beer to remain in its fermenting stage for an abnormally long time. 

Diagnosing Stuck Fermentation 

Because there are so many potential causes for a stuck fermentation, diagnosing why exactly yours is not progressing can be difficult.

The best way to do this is by testing your gravity and pH levels with a specialized test kit designed specifically for homebrewers. Suppose you find that everything appears normal according to these tests.

In that case, you may want to consider other possible causes, such as inadequate oxygenation before pitching the yeast or higher-than-normal amounts of bacteria present in your wort during fermentation. 

Fixing A Stuck Fermentation 

Suppose you suspect that low oxygen levels are causing your fermentation to stall.

In that case, you can try aerating your wort by stirring vigorously for several minutes or using an aquarium pump and air stone setup to introduce oxygen directly into the brew.

If the temperature is an issue, try cooling down the wort with a cold water bath or using an ice pack wrapped around the fermenter before pitching additional yeast.

Additional yeast may be able to revive a sluggish fermentation, although simply tossing in a fresh pack of yeast may not be significant enough if most of the nutrients have been depleted.

You’re likely to have better results with a method called Kräusening. In this approach, you prepare a small yeast starter, and when it reaches high Kräusen, you add it to the fermenter.

This will introduce more healthy, active yeast cells to the wort and get fermentation back up to speed.

Add a pinch of yeast nutrient and boil the solution for 20 minutes, then top up with boiled water as necessary and cool to about 70 °F (21 °C).

Aerate thoroughly (oxygenation is better) and pitch with a fresh yeast sample; if you have a stir plate, keep the pitched wort continuously agitated.

Maintain at room temperature until it is fermenting vigorously (the so-called high kräusen stage), then add this starter to the beer.

For best results, the beer should have been left in the fermenter during this time so that much of the dissolved CO2 would have escaped.

Finally, if bacteria are causing problems, you can use chemical sanitizers such as Star San or iodine-based sanitizers like Iodophor to kill off any rogue microbes that may be present in your wort. 

What To Do When Your Fermentation Is Stuck 

Check The Temperature 

The temperature of your fermenting liquid will directly affect how quickly the yeast converts sugars into alcohol.

Yeast activity slows down when the temperature drops below 60°F (15°C) and stops completely around 40°F (5°C).

If your beer is stuck, one of the first things you should do is check your fermentation temperatures\ and ensure it’s in an ideal range for yeast activity. 

Check The Gravity 

The gravity of a beer refers to its sugar content—the higher the gravity, the more sugar is present in the liquid.

A low gravity reading could indicate that there isn’t enough sugar for the yeast to convert into alcohol.

If this is the case, consider adding some additional sugar or malt extract to raise the final gravity and give those little yeast something to snack on!  

Check For Oxygen Levels 

Yeast needs oxygen to ferment properly. Low oxygen levels can lead to stalled fermentation. To ensure that you’ve enough oxygen in your wort, consider aerating it with an aquarium pump before pitching your yeast.

This will give them a good starting point for fermentation and help prevent stalls.  

Check The Yeast Health  

Another common cause of stuck fermentation is unhealthy or too little yeast added during pitching.

Make sure you’re using fresh packets or vials of yeast and adding enough yeast cells for proper fermentation—typically 10-14 grams per 5 gallons (18-26 grams per 10 liters) of wort/must/juice is recommended.

You can also purchase yeast nutrient packs specifically designed to help healthy fermentation if needed! 

Insufficient yeast nutrients can also be a factor in stalled fermentation. Ensure you’re supplementing your wort with enough nutrients for the yeast to remain healthy and active throughout the process.

Conclusion

Stuck beer fermentation is an issue that can be frustrating to diagnose and fix, but it is possible!

By checking your beer’s temperature, gravity, oxygen levels, and yeast health, you can get your fermentation back on track and ensure it finishes successfully. With the right techniques and practices, a stuck fermentation can be a thing of the past.

When it comes to home brewing, a stuck fermentation is one of the most common issues brewers face—but fortunately, it’s easy to diagnose and fix!

Low oxygen levels during pitching, high temperatures during fermentation, and bacterial contamination are all possible culprits behind a stalled-out fermenter.