How much head space is too much?

[Brew2Be]

Hi. I'm brewing a stout and I accidentally made a slight crack in my 5L glass carboy so I'm discarding it (I saw the pictures in the horror thread...). Now my problem is; the wort is finished and ready to go into a fermentation vessel, but I only have 3.5L of wort and my other vessels are 10L, 15L and 28L. Obviously my first thought was to just use the 10L vessel, but will that create too much head space? Or wouldn't that matter when the fermentation got going? Or would a better alternative be to buy two 2L water bottles and ferment the stout in them?

Thanks in advance!

Brew2Be

 

[jesserizzo]

The 10L would be fine, since as you surmised, once fermentation gets going it will push all the oxygen out of the vessel.

 

[Brew2Be]

Great! Thanks for your reply!