kanzimonson
Well-Known Member
I'm having doubts about a common brewing concept and I'm hoping somebody with some more chemistry/physics experience can chime in.
I'm doubting that the CO2 created during fermentation truly creates a thick, impenetrable blanket over the top of our wort. Yes, CO2 is denser than air, and overall I think that the airspace in our fermenters stratifies into layers with mostly CO2 towards the bottom. I just don't think it's a 100% layer of CO2, on top of which is a layer of air.
Take the earth's atmosphere as a whole. If all the different kinds of gases in air separated into layers, then we'd be living on the surface of the earth under a CO2 blanket as well (or some other dense gas).
In wort, people seem to think of it like oil and water - almost instantaneous separation, but I think a better analogy would be something more like combining honey and molasses - they have similar densities, but not exactly the same, they flow but slowly, and they mix (slowly). If you added honey to the bottom of a container of molasses, the honey (it's denser) would force MOST of the molasses out the top, but there would be a little mixing.
This principle is basically the reason why we "purge" our kegs with CO2 three times. Each time you dilute the air content, and by the third time the dilution percentage is so high that we might as well say there's no air in there.
Anybody have any real insight into what this actually means for our fermenters and other applications?
I'm doubting that the CO2 created during fermentation truly creates a thick, impenetrable blanket over the top of our wort. Yes, CO2 is denser than air, and overall I think that the airspace in our fermenters stratifies into layers with mostly CO2 towards the bottom. I just don't think it's a 100% layer of CO2, on top of which is a layer of air.
Take the earth's atmosphere as a whole. If all the different kinds of gases in air separated into layers, then we'd be living on the surface of the earth under a CO2 blanket as well (or some other dense gas).
In wort, people seem to think of it like oil and water - almost instantaneous separation, but I think a better analogy would be something more like combining honey and molasses - they have similar densities, but not exactly the same, they flow but slowly, and they mix (slowly). If you added honey to the bottom of a container of molasses, the honey (it's denser) would force MOST of the molasses out the top, but there would be a little mixing.
This principle is basically the reason why we "purge" our kegs with CO2 three times. Each time you dilute the air content, and by the third time the dilution percentage is so high that we might as well say there's no air in there.
Anybody have any real insight into what this actually means for our fermenters and other applications?