Effect of Keg Headspace on Carbonation

[ESPY]

I'm considering using sugar/DME to prime in the corny keg on a batch of brown ale that's close to being ready. I've never done this before - I've always just carbed the keg with CO2. I know that the general rule is to use less priming sugar in a keg than you would for bottling (despite some posts I've seen suggesting low carb levels result from this). But I also like to bottle a dozen or so 12-oz bottles and I don't have a counter-pressure filler.

So what I'm considering is priming both the keg and the bottling bucket with the appropriate amounts of sugar and then racking into both.

But I will abviously end up with a little less that 4 gal in the keg. I know that I'll need to purge the air, but I'm more concerned about the amount of headspace I'll have in the keg and what effect this will have on my carbonation. Anybody know?

 

[david_42]

The head space would be about 1/4 the volume, so you would need about 3/4 of a volume of extra CO2 (assuming a 3 volume carbonation level). I would just prime the whole batch for bottling and keg the leftovers. Worst case, you can release some pressure on the keg. Can't do that with bottles!

 

[ESPY]

OK, so more headspace requires more sugar. Sounds like you're right...the easiest way to do it is just prime the keg with the normal bottle amount.

I like that option because I can put the priming sugar in the keg, rack into the keg, then fill the bottles right from the keg. That way I eliminate the need to rack an estimated amount into the bottling bucket which usually results in a partially-full bottle.