This is an age-old question, should you transfer your fermented beer into a second vessel prior to bottling or kegging it?
Many recipes found in books and online recommend transferring a beer to secondary within 3 days of fermentation. Some recommend doing it a week later. Lately there has been a ground swell of home brewers saying that secondary is dangerous and should be avoided. We ourselves have debated it and have changed our minds on the topic more than a few times. Here is our current opinion on the debate.
First of all, what is primary and secondary?
Primary: Where the initial fermentation happens. This is where the wort produced on your brew day is placed and the yeast is added. Most often it is a pail, sometimes a carboy or another vessel. Airspace is required in this vessel as vigorous fermentation occurs in it which can bubble up considerably. Typically, beer fermentations are finished within a few days, and then require a rest period. Beer can be safely left in primary for about 3 weeks. Some people argue that it can go longer, but we recommend targeting a max of 3 weeks.
Secondary: Secondary is the … second vessel the fermented beer goes in. The idea behind secondary is to transfer the fermented, but not clarified or finished beer into a new clean vessel that gets it off the yeast. Beer can be stored in secondary much longer than in primary. Typically, very little fermentation happens here, but dry hopping or fruit additions are often done in this stage. The big benefits of secondary are clarification, safe storage conditions, and flavour additions (dry hopping).
What is the debate about?
It all comes down to time and oxygen.
Is secondary actually useful? Or could it do more harm than good?
Once fermentation has started, oxygen is the enemy of your beer. Beer exposed to oxygen for even a short period of time can take on some negative flavours, such as sherry like or cardboard. In extreme cases it can taste like burnt caramel. Oxygenation is by far the most common fault in home brewing. It is very easy to oxidize beer. Once a beer is oxidized, the best place for it is down the drain. There is a much higher risk of getting O2 in your beer when secondary is involved.
During primary fermentation, the oxygen inside the fermenter is eaten by the yeast during the first phase. As the beer ferments, the oxygen is replaced by CO2. The airlock on your fermenter allows excess CO2 to escape the fermenter without allowing any oxygen into it. With a layer of CO2 on top of a beer it is safe from oxidization. Once the primary fermenter lid, or bung is removed; the CO2 layer on the beer may disperse. At this point the beer is very vulnerable to oxygen.
Next, the empty carboy that is being racked into is full of oxygen, and the beer is going to integrate with it as it is racked. Then, it is unlikely that the beer racked into the carboy will be filled to the top. Meaning, there is a lot of oxygen just sitting on the beer. Even a day in this situation can be enough to oxidize the beer. Prolonged contact time will make it worse.
The beer may be clarifying nicely, but it is also being oxidized to the point where it tastes awful. That is not a good trade-off.
Are there ways to improve racking? Absolutely and we’ll get into them further below. They do require special equipment that adds up financially.
The way to make it work in Primary:
Secondary is largely unnecessary, especially if you are bottling your beer. The beer is safe in primary for about 3 weeks.
The big advantage to secondary is that it greatly improves clarity in the finished product. This does not matter much when it comes to naturally carbonated beers (adding dextrose or DME in a bottling bucket and letting the beer carbonate in-bottle). The reason for this is that when a beer is carbonating in bottle – it is fermenting again, and fermentation inevitably produces sediment and debris. Regardless of how clean the beer is going into the bottle, it will have sediment in it after it is carbonated. So, why bother clarifying the beer in secondary and taking the oxygen risk when the clarity will not be improved in the finished product?
To properly clarify bottle carbonated beer is to let it carbonate properly until all of the bottles are fully carbonated (2-3 weeks typically) and then put the beer somewhere cold (0°C or higher) and the beer will clarify and in a safe manner. Feel free to consume the beer anytime, the longer it sits the cleaner it will be. Though we recommend not letting it sit past 6 months.
If you’re kegging, then secondary does have some benefit. Unlike with bottle carbonating, beer in kegs is carbonated by directly applying CO2. Beer that goes in clean will stay clean, and beer that goes in dirty will clarify a bit, but the sediment will still be in the keg. Aging a beer in secondary (especially at cold temps) for a week or two will really help with clarity.
What about oxygen in secondary?
If you’re kegging, it also means you have CO2. That CO2 can be used to in the racking process to limit oxidization.
Using CO2 in racking:
First of all, before siphoning beer into a carboy. Fill the carboy full of CO2 from your tank, we typically just remove the ball lock adapter (grey one) and let the open gas line shoot CO2 into the carboy. Do it for about 10 seconds before pulling the hose out and placing a bung and airlock on top. This will keep the CO2 in the carboy as you prepare the siphon.
Siphon the beer into the carboy, and once it’s all in there, lay a layer of CO2 on top of the freshly racked beer. Do this for about 10 seconds and then place the bung and airlock in the hole. You should see the airlock bubble a couple of times – this means that it is letting a bit of excess CO2 out.
The beer will be safe in this condition for a few weeks if not longer, it doesn’t hurt to top it up with a bit more CO2 after a few weeks. We use this technique all the time and it leads to significantly better tasting beer.
It is our view that if you are bottling your beer, it is much better to proceed directly to the bottling stage from primary. This will accomplish a few things: 1) prevent oxidization and 2) get you drinking your beer sooner!!!
If you are kegging, secondary can still be a useful part of the process. Especially if you are making a beer that really benefits from great clarity like a lager, or blonde ale. Just be sure to be careful when transferring the beer, when in doubt, lay down a layer of CO2.