Wed Oct 01, 2008 6:14 pm
When in doubt, wait. Don't rush the primary. Yeast works on it's schedule, not yours. In homebrewing we don't really do a secondary fermentation anyway. Secondary fermentation actually involves adding more fermentables and restarting the fermentation.
What we normally refer to as a secondary fermenter is actually a bright tank, i.e. a tank to which a beer is transferred where it is allowed to drop clear (hence the name "bright") and get a bit of age. You need to let fermentation go to completion in the primary fermenter. Once you get to your expected final gravity you can either transfer it to a bright tank to finish clearing and perhaps drop another point or two.
A lot of us don't even bother with a secondary any more for most beers. The early transfer of beer to secondary is due to overblown fears of leaving a beer on dead yeast too long. This phenomena, known as autolysis, causes a burnt rubber taste in the beer. To avoid this, many older texts (and brewers) will tell you to transfer after a week. In reality, autolysis won't even begin to show up for at least 6-8 weeks. I routinely leave my beers in the fermenter for up to 4 weeks and still win awards for them. If you transfer in less than a week, you remove most of the yeast from the beer and run a risk of a little higher final gravity than if you just leave it alone.
In short, let your hydrometer tell you when to transfer out of your primary. Once you get the same reading a couple days apart, the time is right (assuming you are close to your expected final gravity.)
Wayne