I was reading Papazian's Joy of Homebrewing and in several sections he references "closed fermentation" and "open fermentation." One brief and rather crpytic section is called "Open versus Closed Fermentation."
What, exactly and in one sentence, is "closed fermentation." Likewise, in one sentence, what is "open fermentation."
I've read the book sections a few times and feel like he does not precisely define these terms precisely enough (at least for a novice like me), though the book overall excellent, I think. This is the only thing I don't get.
Is open fermentation simply a method which is done with no lid on the fermenter, or, is it any fermentation process - regardless of a lid being present or not- that allows the krausen to fall back into the beer? thanks for any help