I make some small batches of home-made cola, tonic water, and ginger ale - usually making a batch of syrup, then mixing up a corny keg full and force-carbonating it over a few days. Normally I bottle and sell these at a market, so having a keg of each is a good amount.

I've just had someone wanting to place a small order - roughly half a keg's worth of bottles. I'm hoping I can just make up a half-keg, and force carbonate it as normal, but is there anything I should consider before I try?

Some specifics:

* Will the extra head space in the keg have any effect?
* Will I need more or less pressure?
* Will it take more time or less?

I have been pressurising a full keg up to 45psi for 72 hours, with some gentle agitation whenever I remember to do it. This yields a nice gentle carbonation that I'm happy with.

The drinks don't stay in the keg any longer than required to carbonate and bottle - 72 hours, tops.