Resurrecting an old thread here...
Headspace, I get it, I understand the whole "oxidation" concept and why you would want to minimize headspace under "normal" circumstances... unfortunately, I have NEVER been accused of being Normal...
Is the whole "headspace" discussion overcome by events if I keep a pad of CO2 on the must/ageing wine? I use a conical fermenter for secondary (and sometimes primary) and it kind of defeats the purpose of using a conical if you transfer it to a carboy for clearing. (I normally clear in the conical, and transfer to a corny keg for cold crashing and eventual bottling)
While in the conical, I routinely use a CO2 bottle to "replenish" the CO2 pad on the surface of the liquid, ESPECIALLY if I do something to disrupt it, such as stirring drawing samples, etc. I also try to "fill" the collection jar with CO2 when changing it so as not to force a big bubble of O2 containing air through the center of the must. Does this not eliminate or at least diminish the concern over headspace?