Primary Fermentation

Looking for more information about primary fermentation? This is the definitive post to answer the questions of what it is and how long it should last.

Definition of Primary Fermentation

We define primary fermentation as the process of introducing a fermenting microbe to your wort or must until its process is complete or interrupted/merged with a second process.

How Long Should Primary Fermentation Last?

For homebrewing beer, the length of time for fermentation can vary.  If you are a beginner homebrewer and you are brewing an ale that doesn’t have a high starting gravity (less than 1.070) from a recipe kit, you should let your primary fermentation last 2 weeks. Just leave the beer in your primary fermentor for 14 days as a good rule of thumb.

There may be recipe kits out there that have instructions to only ferment the beer for 1 week and then bottle.  For example, when we started homebrewing over ten years ago – we followed recipe instructions from our local homebrew shop kits that had the one week fermentation step.

Over the years, the two week standard has served us well. Again, this is a good guideline for most ales that you brew when you first start out homebrewing.

Here are some points to keep in mind:

  • A fermentation duration of two weeks is not a rule. It could take shorter or it could take longer. The duration is determined by many factors including the yeast (strain, health, and count), your wort, and the temperature.

The best way to know that your fermentation is done is to take a gravity reading to see if your beer has fermented to its target final gravity.

Get tips on how to take gravity readings during fermentation!

  • In our experience, two weeks is better than one; we have had better results with two weeks than one. It gives the yeast more time to reprocess some of the early stage fermentation byproducts and time for the yeast to settle out.
  • Keeping your beer in one fermentation vessel for two weeks and then bottling or kegging is ideal. By skipping a secondary vessel conditioning phase, you are eliminating a chance for contamination. Also, we are of the opinion that conditioning most ales in a secondary vessel provides little to no flavor enhancements to the final beer that you can get from bottle or keg conditioning.

Follow this link to read more about secondary fermentation and when to skip the step.

  • We feel that secondary vessels should be used for high gravity beers, for lagering, for beers that are going to have post-fermentation additives (dry hopping, fruit, spices), and for beers that call for the addition of a second microorganism intended to feast on sugars that the primary strain does not.  You should use them for certain techniques or beer styles.  The point is, for most ales, a two week primary fermentation is all you need.

Primary Fermentation

Hopefully, this post has helped you out.  Please leave a comment below if you have a specific question for us to answer.  Brew on.