The question about secondary fermentation has been around as long as someone popped open a carboy and thought, “Let me make more work for myself”. All joking aside, there are some legitimate reasons to use a secondary fermentation. But first, let’s go through just what exactly secondary fermentation actually is.
What is Secondary Fermentation?
In it’s simplest form, a secondary fermentation is really just a second fermentation that occurs in a separate vessel than primary which ranges from several weeks to several months. Some brewers argue that this allows beer to “smooth out”. It could also be done so complex flavors from additions (fruit or additional hops) or a very high gravity beer to meld together.
Is secondary fermentation necessary? When should you do secondary fermentation vs keeping it all in one for the primary?
The short answer: no. It’s not necessary. Like many things in homebrewing, there are certain reasons why you would want to do a secondary fermentation. This depends mainly on the flavor and style. However, you can make just as good beer using only a primary vessel vs doing one in an additional secondary. A secondary increases the cost because you need additional fermenters. It also increases time spent cleaning equipment. With that said, there are solid reasons to use a secondary fermentation.
Here are three reasons to do secondary fermentation
Fruit Additions or Dry Hopping
Dry hopping or adding fruit additions is more effective when you remove the beer from the yeast sediment. It helps for a few reasons including not stirring up the yeast cake (at the bottom of the fermenter) and allowing the beer to be enhanced with the full flavor of the fruit or additional “dry” hops.
Some people use dry-hopping within the keg, however clean up is already a pain the ass and I personally wouldn’t want to complicate it by having hop particles stuck in various tubing. Although you can probably prevent this using a hop sack and not dumping hops in directly in the keg.
Extra Clear Beer
I personally use a combination of Irish Moss (Amazon Link) and cold crashing when it comes to clearing up beer. However, you can also transfer the beer from the primary fermenter into a secondary fermenter to enhance the clarity. Many breweries also do this in what they call either a “bright tank” or a “conditioning tank”. This allows the beer to mature. Some folks also use gelatin which acts to form the proteins together and results in clear beer.
High Gravity Beer
Certain beers require a long aging period (think Russian Imperial Stout, or an 8% abv Bourbon Barrel Stout). This extra time allows the beer to mellow in flavor. It can aid with the harsh alcohol taste that can be intense. The hardest part with these is waiting so long to be able to try it. Due to the extra time allowing the beer to mature, many folks recommend that the beer is removed from the yeast cake that is present during primary fermentation. This helps to avoid any potential off flavors. Sometimes brewers also want to reuse the yeast and removing the beer prevents any additions from impacting the yeast cake.