I was looking at a 1 gallon jug the other day (I ferment in them) and something grabbed my interest. I can really shake the bejesus out of them to oxygenate.
Some of the discussions that have evolved out of the "Shaken, Not Stirred" discussions involved the O2 demands of the majority of the brewer's yeast available to homebrewers. Mark has stated a few times that most of these strains are Class O1 or O2 strains with respect to O2 demand (4-8 ppm).
I'm no super brain but it would seem to me that those of you using ~5 gal buckets and carboys would have a hell of a time shaking that vessel and getting the kind of foam I get shaking my 1 gallon jug. 5 gallons of water weighs about 40 lbs. and a carboy an additional 10 lbs. or so.
I guess my question is this: For those that shake or swirl the carboy/bucket, is it even possible for you, given the weight of the liquid and the vessel combined, to shake/swirl vigorously enough to reach saturation? Obviously a MixStir or Pure O2 will get you there no problem, and in the absence of a DO meter, this post is a moot point, but I couldn't help but entertain the thought.