Why 1/2 the priming sugar in keg?

[blackbear219]

I've been reading about naturally carbing a keg and everyone says to use half the priming sugar that you would if you were bottling the batch. Why is this? You would think that if you are carbonating the same volume of beer it would require the same amount of sugar.

 

[blackbear219]

Well, I just revised my search criteria and I was able to find the answer. It's because of the reduced headspace apparently. Makes sense.

 

[944play]

Well, and, apparently, because of the fact that when bottling, the beer is agitated more than when kegging. Agitation helps CO2 escape. Additionally, when you close a keg you generally add a shot of bottled CO2 to verify the seal and add positive pressure.

Logically and experientially, I find the "use half" notion to be erroneous, and somewhere between urban myth and an appeal to caution (to avoid overshoot; while it's easy to add artificial CO2, it's a pain to purge excess). I've always used the calculated amount (or just the LHBS bag of bottling sugar) the few times I've primed kegs and they end up merely as carbonated as the math projects.

 

[Malticulous]

Less head space.