Demijohn headroom to avoid oxidation

[JimboMarimbo]

Primary fermentation just completed at 0.998 - apple wine shows no movement or bubbles, great result - 17.94%!. It took 12 days in primary bucket,and I syphoned off the total of 7L into two demijohns: trouble is, they are only about 75% full and the headroom, now that C02 production will have ceased, is causing me concern, fearing oxidation of surface layer.
I would appreciate advice - should I fill DJ (1) to the near top and leave the balance in DJ (2) with a 6" , 15cm empty headroom, or ditch the second DJ and fill a 2L plastic mineral water bottle to the brim instead.
I was hoping to mature 'in bulk' as many here have advocated, but am uncertain how to proceed with only 7L finished liquid..

 

[Raptor99]

or ditch the second DJ and fill a 2L plastic mineral water bottle to the brim instead.

The best solution is to fill one carboy to within 1 inch of the top, and put the rest in a smaller container. Once you start aging, minimal headspace is important.

But I would be hesitant to use plastic. You can use 750 ml or 1.5 L wine bottles for bulk aging. The right sized stopper (#2 I think) will fit into them. Or maybe you can find a 2L glass jug. It's good to have several different sizes of containers for bulk aging, so that you can fill them to the top.

 

[JimboMarimbo]

thank you for that - I had worried about plastic (food grade) bottles for long term storage - I'll stick with smaller glass bottles and fill 'em to the brim as you advise.