Priming in a keg

[beerbrent]

Hi,
I would like to know if i can prime my beer in a keg. I used two 2.5 gallon corney kegs for my 5 gallon batches. can i prime in a keg? I do force carbonate but my co2 tank is hooked up to two other kegs in my fridge and i got two more kegs that need to get gassed. My manifold only has two outlets. So can i prime in my kegs and if so how much corn sugar do i use, the same as if i was bottling? say 2.5 volumes is what i need.

[Nyakavt]

You can indeed prime in a keg, you just have to make sure that your keg seals well with no pressure. A good test for this is to fill it with some liquid, close it up, and turn it upside down. If any liquid leaks out then the seal is probably not good enough. Keg lube can help with this to some extent, and you also want to make sure the mating surfaces of the keg lid and keg body are nice and flat. If you can, give the keg a shot of CO2 to help seal the lid. Some of this CO2 will be absorbed by the beer but hopefully by then you will start building positive pressure from the sugar fermentation. This step is not strictly necessary but you want to give yourself every chance at success.

You use the same amount of sugar you would use in bottles. I've heard other brewers cutting the amount of sugar in 1/2 when keg priming, but this doesn't make any sense to me. The yeast will produce a fixed amount of CO2 from a given amount of sugar, the size of the vessel is irrelevant. It could be that they are transferring before fermentation is completely done and getting some 'bonus' CO2 from residual sugar in the beer. Either way, I've primed a couple of kegs with the regular amount of sugar and it has produced the expected level of carbonation.

Last words of advice, chill the beer down to serving temp for 24 hours before you purge, that will allow some additional CO2 in the headspace to be absorbed into the beer. Make sure you purge the keg before connecting to your gas lines, as it will almost certainly back up beer in the gas lines if you do not.