So, it occurs to me that I have an oxygenation stone, to saturate wort prior to fermentation. Saturating fermented beer with CO2 is not much different a process. Is there any reason it wouldn't work to use a CO2 tank with the oxygen stone to re-carb flat beer (say, from a growler I sat on too long)?
I would say any CO2 you injected with a stone would be at the door quicker than a hooker you paid in advance. What you are attempting would result in the equivalent of residual CO2 (no headspace pressure) in your growler. This is the point where the CO2 dissolved in the beer (essentially water) is equal to the dissolved CO2 in the atmosphere. At one atmosphere in your growler (unpressurized) the CO2 will move in the direction from highest to lowest until there is equlibrium. At normal beer serving temps this equlibrium is 1.3 to 1.4 volumes. This is what we call "flat beer". With keg pressurization the headspace pressure forces the CO2 to move from higher headspace (12'ish psi) to the lower pressure in your beer (water). At some point they equalize and your beer is carbonated as intended. If you inject CO2 in an unpressurized carboy it will escape into the headspace and equalize with atmospheric CO2 levels which will cause great distress to the drinker. To make maters worse, the air that enters the growler after every pour has the dreaded you-know-what gas that makes your beer taste like cardboard.
How about for a shorter term fix, like in the glass when I pour it? Will it last long enough for me to get through a pint? I'm not trying to revive a flat growler to throw back in the fridge, I'm thinking more in terms of "if I got a flat growler in a trade, could I fix it, or am I just going to drink flat beer?"
I would be doubtful if it would work, but there is no harm in trying . . . almost tempted to try it myself. Getting the beer as cold as possible can only help. One possibility is to "purge" the headspace of your growler with CO2 after a pour. This is not pressurizing the growler but trying to prevent oxidation by forcing the air out . . . may help with longevity.
Good call, and while I like the advice for longevity. Today though I'm only trying to solve the "I want to drink it right this minute and it's flat" problem.
