Use your hydrometer and measure the SG. Compare that with your expected FG (should be specified in the recipe). If it's in range of the FG, take another reading a couple days latest to verify no more activity.
The hydrometer is the only way to know for sure that your fermentation is done.
Originally Posted by IrregularPulse
I'll make my buddy do it with me next time. That'll make me go harder at it.
"If guns don't kill people, why do we give people guns when they go to war? Why not just send the people?" - Ozzy Osbourne
Sent from my iPhone 4s.
Canon T2i | EF-S 18-55mm | EF 28mm 1.8 | EF 50mm 1.8 | EF-S 55-250mm
3 whipped dog straights, Gillette Ball End Tech, 1959 Gillette Fat Boy
Secondary: Strawberry Melomel