Gravity......the krausen will drop when you are near gravity. If it has krausen it means the yeast are still working. SO you want to leave them alone and let them do their job.
In Mr Wizard's colum in BYO recently he made an interesting analogy about brewing and baking....He said that egg timers are all well and good in the baking process but they only provide a "rule of thumb" as to when something is ready...recipes, oven types, heck even atmospheric conditions, STILL have more bearing on when a cake is ready than the time it says it will be done in the cook book. You STILL have to stick a toothpick in the center and pull it out to see if truly the cake is ready.....otherwise you may end up with a raw cake....
The only way to truly know what is going on in your fermenter is with
your hydrometer. Like I said here in my blog, which I encourage you to read,
Think evaluation before action you sure as HELL wouldn't want a doctor to start cutting on you unless he used the proper diagnostic instuments like x-rays first, right? You wouldn't want him to just take a look in your eyes briefly and say "I'm cutting into your chest first thing in the morning." You would want them to use the right
diagnostic tools before the slice and dice, right? You'd cry malpractice, I would hope, if they didn't say they were sending you for an MRI and other things before going in.
That's how you'll know when to rack...or you can do like a lot of us do, and leave your beer in primry for a month then bottle.
Not too different from our beers....We can have a rough idea when our beer is ready (or use something silly like the 1-2-3 rule
(which doesn't factor in things like yeast lag time or even ambient temp during fermentation) and do things to our beer willy nilly....but unless we actually stick "our toothpick" (the hydrometer) in and let it tell us when the yeasties are finished...we too can "f" our beer up.
We forget this simple fact...We are not making koolaid, or chocolate quick, just stirring in and having instant gratification...when you pitch yeast, you are dealing with living micro-organisms...and they have their own timetable, and their own agenda.
