Any issues 1/2 filling FV?

[naturals]

Hi all, so far I've been doing my fermentation in 1 gallon glass demijohns. I'm a little tired of cleaning the things out and the floorspace that loads of demijohns take up so I bought a Wilko's 25L FV. For my next brew I'm hoping to do a half batch (11-12 litres) of porter circa 6-7% ABV. Can anyone tell me whether I can use the large FV for this? Will having too much headspace negatively impact my brew? I'm thinking the high OG needed to get to that alcohol percentage should encourage the yeast to fill the dead space with CO2 pretty quickly. I'm going to be making a yeast starter 12-24 hours before I need it to encourage fast uptake. Is this enough?

 

[Jeltz]

It shouldn't cause you any problems, my next planned brew is a 20L one which several of our brewing club are doing to see how technique impacts on how the brew tastes, it has lots of hops so and some people ended up with 17L, if I do the same I'll be happily popping that into my 33L bucket.

 

[evanvine]

The more head space you have, the larger the volume of CO2 protecting the brew.
Well that's my theory.

 

[rpt]

CO2 is heavier than air so once there is enough to cover the wort it doesn't matter how big the FV is.

 

[DanT]

No problem filling the FV halfway just be wary that if you (even though you already said you use demijohns) use a keg, that will also only be half full at the most. That just means you won't have any pressure to make the beer flow and will need to force carbonate it a bit to help it along. You'll get some carbonation in the beer from priming, but no pressure (I have a half keg now).

 

[markmark]

I use a 70 litre fermenter for 40-45 litre batches.
My theory is that the headspace saves the clean up from some over exuberant yeasts and gives SHMBO one less opportunity to moan at me :lol: