Digression from What's the point of secondary fermentation?
What are the good rules of thumb for determining a. whether to use secondary fermentation at all and b. when to move from primary to secondary.
Preferably any rule of thumb should have both chemical and anecdotal rationale supporting it.
From John Palmer in the "Ask the Experts" section of the AHA forum:
Therefore I, and Jamil and White Labs and Wyeast Labs, do not recommend racking to a secondary fermenter for ANY ale, except when conducting an actual second fermentation, such as adding fruit or souring. Racking to prevent autolysis is not necessary, and therefore the risk of oxidation is completely avoidable. Even lagers do not require racking to a second fermenter before lagering. With the right pitching rate, using fresh healthy yeast, and proper aeration of the wort prior to pitching, the fermentation of the beer will be complete within 3-8 days (bigger = longer). This time period includes the secondary or conditioning phase of fermentation when the yeast clean up acetaldehyde and diacetyl. The real purpose of lagering a beer is to use the colder temperatures to encourage the yeast to flocculate and promote the precipitation and sedimentation of microparticles and haze.
So, the new rule of thumb: don’t rack a beer to a secondary, ever, unless you are going to conduct a secondary fermentation.
There are two things to consider when racking to secondary:
Wait for primary fermentation to finish. The common rule of thumb is to wait until the gravity of the beer doesn't change over the course of three days. This will indicate that the primary fermentation has completed. However, it's helpful to leave your beer in primary a little longer, even after fermentation has finished, to...
Allow the yeast to clean up byproducts in the beer. During reproduction and fermentation, the yeast product a number of byproducts that can contribute to off-flavors and instability in the beer. After fermentation is complete, the yeast clean up these byproducts. If you rack off of the yeast cake too early, the yeast won't get a chance to do this housekeeping, and you'll end up with undesirable compounds in your beer.
For most beers, I personally leave my beers in primary for no less than two weeks--often more for bigger beers--before racking to secondary or bottling. It's always better to leave the beer a little longer in the primary than to rack too early. Autolysis (the process by which yeast break down and die) isn't really a problem for homebrewers, unless you're keeping your beer on the yeast cake for many months to years.
The current recommendation from homebrew experts John Palmer and Jamil Zainisheff is to never use a secondary unless you are doing an actual secondary fermentation...i.e., adding additional sugars or fruit. The previous ideas that you should move your beer off primary quickly came from commercial brewing examples. since we don't have fermentations on the same scale, that recommendation doesn't apply to us.
Using a secondary is a matter of preference for the brewer and the style of brew. While I highly recommend using a secondary it is not required.
You move to secondary after primary fermentation is done. This is usually determined by taking specific gravity readings and once they've been the same for 3 days primary fermentation is considered complete (~2+ weeks).
Secondary is used to clarify the beer and allow spent yeast and other materials to settle to the bottom for clearer beer and to prevent off tastes. It is also a good time to do things such as dry hop, add oak chips, or any other aging flavor. Secondary is usually done for around 1-2 weeks.
I've heard that beer can stay in the primary for several weeks, but I continue to rack to a secondary. I usually do it as soon as the head has died down and I'm pretty sure it's not going to flare up again in the carboy. I like to get the beer away from the grungy primary and get the primary cleaned. (I use a plastic pail for primary, and glass carboy for secondary.) And I like to do it quite early so that there will be plenty of CO2 still coming out of the beer to force the 02 out of the carboy. I usually let it sit a days or two, and then top it up with water.
I think there is still plenty enough yeast in suspension to do the clean-up mentioned by Jeff L.
I often bottle 2 or 3 weeks later. And though I know I probably don't need to use a secondary at all in those cases, I like to do it anyway. It's party aesthetic.
Some widely respected people advise against it, like:
Racking to prevent autolysis is not necessary
Whilst it might be true, in some cases, it is not true in case of strong stuff, stuff that will stay in fermenter long time. See wine resources - for yeast wine with nutrient is not so different than wort. And even if this particular part, this one reason is true - racking may be performed to prevent other undesired tastes, including ones that came from badly filtered wort, from leftover hops etc. I think we may safely assume that experienced and knowledgeable people hardly ever have such problems anymore, so for them it doesn't matter. At the same time if you still wonder, you might be far from that state. Or not.
Brew something simple. Like APA, or other balanced beer. And do it twice, with and without. It is not expensive nor especially time consuming, but it'll let you know what works better with your workshop and your skills.
I did this, and I tested it on my friends and myself. Racking to secondary created beer that was received better, and was ready to drink faster. Does it mean I can't filter properly? Maybe. I know I can't, or at least couldn't until my last batch! Or maybe I have some other issue? Who knows. But when it comes to beer, no amount of respectability will ever win with taste-buds of my friends, and that's approach I strongly advise to you.
If you want to brew real ale, you simply have no option other than to rack. Of course you probably will not rack to actual cask, but cask had inside covered with substance that prevented beer from acquiring wood taste. But historically, English ales was racked, and kept that way for period of time similar to our "secondary". And it was famous. Of course there are ways far faster than traditional ones, but that's not why we do it, is it? I'd say it's quite the opposite...
If you add Gelatin or other clearing agents to primary, your yeast are pretty much wasted. Can't use them to next beer, because you will harm their ability to stay in suspension. And even if you won't, leaving yeast too long in beer that's almost finished may make them dormant. Or dead. So if you are brewing chain of beers to prepare good slurry for barleywine, racking will be the way to go for you.
If you use a non-transparent plastic bucket or carboy for your primary, moving it to a transparent plastic or glass carboy allows you to see the clarity of the beer before bottling. You will be able to bottle your beer when the desired clarity is reached. In most cases, moving to a secondary is purely cosmetic.
An interesting point when considering initial and possible secondary fermenter:
If we’re going to let the beer sit after its main fermentation is done, it pretty much needs to be in glass, and away from the spent yeast that accumulates at the bottom of your fermenter. - Secondary Fermentation, Pros and Cons.
I am a noob focussing on IPA, and so far have only made a 1/2 dozen batches.
After trying both approaches - with secondary and without - I find I get a cleaner and more crisp beer using the glass secondary. So I think if you are doing all the work to make a good batch of beer already - and you are going for the cleanest filtered result, it is worth the additional medium effort it takes to have a secondary as part of the process.
In my case , I have four 1-gallon glass jugs for that. So although there are four bottles to fill up and empty, I find it easy to move them around and whatnot.
In contrast to @Jeff L, I'd read in CJJ Berry that when brewing wine, it's advisable to rack off fairly early to prevent wine sitting on dead yeast and being contaminated by undesirable flavours.
My viewpoint is: 1. Rack to a glass 2ndary after 1 week - assuming you have no active carbonation. 2. Dry hop in the 2ndary, although it is a pain if you are using dried hops vs pellets :(
A trusted friend (Dean) who went from "best homebrewer I knew" to successful professional always cautioned me AGAINST racking as "not worth the risk of contamination"
I've been doing 3-5 5g batches a year for over 20 years. I've only ruined one due to contamination and that was NOT racked (it was my 2nd batch and I didn't know how to clean the primary/bottling bucket).
Honestly, I'll probably try skipping the 2ndary on my next simple batch, but I can't every see skipping it if I have a heavy beer with lots of sediment.
This might be another case: if you are doing a batch that will sit in a basement for a year, e.g. a big Belgian strong ale, or the like you most likely need to get it off the yeast cake. A brewing friend of mine did a Belgian Strong Ale a few years ago, and he let it sit in a cool dark basement in primary for over a year. When he finally went to keg it, he said it was ruined due to off flavors (I assume autolysis). Maybe this is an another example of what Palmer means by a "secondary fermentation" but I thought I would mention it (I was so looking forward to tasting that batch).
