Problems about fermenting 1 gallon batch in a 5 gallon fermenter or carboy

[kojinakata]

Hi guys,
Is there any reason for me to not to ferment 1 gallon batch in a 5 gallon plastic fermenter or a carboy? Does the huge headspace (about 4 gallons) have a destructive effect on the batch or is it negligible?

 

[Mozart]

I imagine it varies depending on the gravity of the wort, but I think I've read that one gallon of average gravity wort produces something like 6 gallons of CO2.

If true, the extra headspace shouldn't be an issue, as it'll eventually fill entirely with CO2.

 

[Math0]

It is never a problem when fermentation is open-air (maybe a bit more risky). It would become an issue if you let it age a long time with a big area in contact with oxygen.

 

[C-Rider]

Go to HD and buy a few 2 gallon paint buckets and covers. No more head space worries. And you can almost double your ferment.