Some folks like to add the dry hops during the final stage of primary ferment (90%) to allow the yeast to scrub out any residual undesireables like O2 introduced upon dry hop, allthough I like to dry hop in the keg. Dropping bright is the point of complete primary fermentation when the beer is clear and ready for racking or bottling. The majority of the yeast has dropped out of suspension and active fermentation has ceased.
I'm guessing dry hopping in the keg just keeps more of the hop aroma around, gives it less time to dissipate?
Had a question in the lines of dry hopping... I dry hop when the beer "drops bright" or at least when most activity has stopped since I'm still using plastic and don't see it clear up. I've read a couple of threads (on HBT) with discussions of racking to secondary, and many insisted that dry hopping was one of those times it was important, even if they were against a secondary for clarity, etc. Is there really much to gain from racking to a secondary container/fermenter to dry hop? Or is it just as effective to dry hop in the primary container?