Secondary Fermentation,
is it Worth the Effort?

Do I transfer my green beer for a secondary fermentation or not?  Apparently there is a controversy among homebrewers regarding this question.  I’ve never worried too much about it to tell you the truth.   Part of the controversy is more about semantics than actual mechanics.  The way I see it, I’m not so much transferring my beer to a secondary fermenter as I am transferring my beer to a secondary conditioning vessel.   I believe there are many benefits of transferring your green beer to another vessel for conditioning and clearing.

Determining When to Transfer for Secondary Fermentation

Determining when to transfer will have an impact on what is happening in the secondary fermentation vessel, ie. are you doing a secondary fermentation or are you allowing your beer to clarify and condition in a cleaner vessel? 

1. If you transfer after all fermentation has ended, ie. you have taken gravity readings and they have not changed for the last two or three days, then unless you give the beer another week or two in the primary fermenter to clean up the by-products, transferring to secondary will accomplish the same thing but in a much cleaner environment. 
2.  If you transfer for a secondary fermentation just after the krausen has fallen back into the beer, most likely the primary phase still has a little time left before the beer is fully attenuated.  There will be enough yeast in suspension to fully attenuate the beer and it will do so in a cleaner environment with no yeast cake, bitter gunk on the side of the fermenter, or autolysis to worry about.  
3. If you have given your beer several weeks in the primary fermenter and feel it is time to bottle or keg, then transferring to a secondary fermentation vessel will allow you to do a cleaner transfer to package without worrying about getting the little “floaties” in your bottle or keg.

What's Going On in the Primary Fermenter?

Fermenting in a carboyPrimary Fermentation

So, what’s going on in the primary fermenter when it’s time to transfer?  The yeast have begun to go dormant and settle out to form a yeast cake on the bottom of the fermenter.  The primary phase of fermentation is now winding down or finished. The Krausen has fallen back into the beer, leaving behind a layer of residue on the sides of the fermenter.  This residue is composed of additional wort proteins, hop residue and resins, and dead yeast.  This bitter residue, if stirred back into the beer, could cause off flavors.  But fortunately, they are somewhat insoluble and mostly just stay stuck to the side of the fermenter. There are still fermentation by-products in the beer such as diacetyl, acetaldehyde and DMS that need to be cleaned up by the yeast that are still suspended in the beer.  Most homebrewers do, but you don’t have to do your diacetyl rest in the primary fermenter. 

For a low-gravity ale, it is probably not necessary to rack over for a secondary fermentation unless you want to give the beer more time to clarify and condition.   You probably won’t have to worry about autolysis at this point because you will be racking of the sediment before the yeast begin autolysis.  But, if you have a higher-gravity beer, or your yeast does not flocculate well, you may want to give the beer an extended amount of time to clarify.  Basically you are just allowing the beer to drop bright and get rid of all the proteins and micro-particles that could possibly cause problems with your beer after packaging.

What about Oxygen Contamination?

The major obstacle to racking a young beer seems to be the worry about oxygen ingress and all that entails, ie. Reduced shelf-life, staling, oxidation of malts which reduces malt flavors and aromas, etc.  Nothing good can come from getting any oxygen in your beer at this point.  What I recommend is transferring your beer from primary to secondary with CO2 pressure in a closed system.  To see how to do a transfer to secondary fermentation in a closed-system, take a look at the article  “Closed-System Home Brewing” By Bennett Dawson, Republished from BrewingTechniques' July/August 1994 on the MoreBeer.com website hereor take a look at the instructions for the CO2 powered racking cane kit here.

CO2 Powered Racking Cane Kit from love2brew.comCO2 Powered Racking Cane Kit sold by love2brew.com

Even if you use an auto-siphon to transfer your beer to a secondary vessel, by purging the receiving vessel and laying a blanket of CO2 on top of the beer in the primary, and back-flushing your siphon with CO2, you should be able to transfer from primary to secondary with very little to no oxygen contamination.  Just make sure your hoses are tight so no oxygen can enter the system.

Benefits of Transferring to a Secondary Vessel

If you decide you want to transfer to a secondary fermenter, here are the possible benefits:

1.       For high-gravity beers, an extended aging period is required before the beer is ready to drink.  Because the yeast in the primary fermenter will die and excrete by-products you don’t want in your beer, it is necessary to transfer these beers to a secondary vessel for bulk aging.

2.       It allows your beer to clarify.  Most of the suspended micro-particles will settle out during the secondary fermentation.  Of course, you wouldn’t want to transfer weissbiers or Belgian Witbiers because these beers are supposed to be cloudy.

3.       If you wish to fine your beer with gelatin or another fining agent, and you don’t want to reuse your yeast, you can do so in your primary fermenter and then transfer the clear beer to a secondary vessel for further aging and conditioning or to crash cool and package.

4.       If you ferment in a bucket, transferring to a secondary clear carboy will allow you to get a good look at your now clear beer and do a better job of racking to a keg or bottling.

5.       You can add oak, dry hop, or add fruit or other flavorings while there is not enough CO2 present to gas-off the volatile notes you want to keep in your beer.  Plus, you can now leave the beer on the oak, fruit or hops for an extended time without worrying about yeast autolysis.

6.       If your primary fermentation is stuck, or you feel it should attenuate more (based on your forced fermentation test), you can rack to a secondary fermentation vessel and add more yeast without worrying about all the gunk and dead yeast in the primary fermenter and how it might affect your beer. 

7.       Racking to a secondary glass carboy will prevent any oxygen ingress that could happen if you wish to age or condition your beer and your primary fermenter is a plastic bucket.

8.       For those beers with gravities that are in between session and high gravity, say 1.065-1.08, it may be prudent to give these beers some extra aging time.  I realize that they are not high-gravity beers that will require long aging times to fully condition, but they are not session beers that are ready to drink in a few weeks either.  So, I would rather err on the side of caution and give these medium-gravity beers plenty of time to condition.  It’s not going to hurt the beer, whereas transferring to keg or bottling too early might.

Conclusion:  If you transfer your beer from a primary fermenter to a secondary vessel using the closed-system method, and you can’t use oxygen contamination as an excuse, then the only drawback will be the extra time and an extra vessel to clean.  I know that some prominent homebrewers don’t recommend that you ever transfer an ale to a secondary fermenter, but if you feel the benefits outweigh the possible drawbacks, it’s your beer and you must decide the best course of action for yourself.  Most of the time, I’ll allow plenty of time for the beer to finish fermenting and clean-up the diacetyl and other by-products of fermentation in the primary fermenter, usually about two to three weeks.  Then I’ll almost always transfer to a secondary vessel and crash cool it in the fridge.  This allows the beer to clarify and cold condition prior to packaging.  I have fined with gelatin in primary before transferring to the secondary but most of the time, I’ll add gelatin to the secondary and transfer from there to a keg after its dropped clear.  But, everyone does things differently and what works for me probably won’t work for everyone else.   

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