I use carboys and no cooling, I keep 1/2" once fermentation is over.
I just adjust the level with temperature variations, topping off or
removing.

I think that is the safe play, as temperature variations in our house
rarely exceed 20 F over a year where my wine is made. I will cold
stabilize outside this year. When I do that, I put vodka in the
airlocks and top after the first day.

Our winters can get cold, so outside temps vary from around 95 to 0
over the year worst case.

Even if I don't take it outside I get a lot of tartrate out of
suspension at 50F over several months.
Regards,
Joe

"Negodki" > wrote in message >...
> > "Karen Lambert" > wrote:
> > how much is too much air space?
>
> > "Negodki" > wrote:
> > . . . . If you can be sure that there will not be
> > such a temperature increase (even if there is a power failure and your
> > refrigeration system goes south for the winter), you could use 1/2-3/4"
> on
> > all vessels, but the same surface area would be exposed, and there would
> > be little difference in oxidation. . . .
>
> "Lum" > wrote:
> > Wouldn't the amount of oxygen available be proportional to the _volume_ of
> > the head space, and the _rate_ of transfer to the wine would be
> proportional
> > to the surface area?
>
> Yes, but in the narrow "bottle-neck" of a carboy, there isn't much surface
> area exposed. So, I think, the rate-of-transfer is slow enough, and the
> volume-of-air : volume-of-wine ratio small enough, that there will not be
> much noticeable difference in oxidation between a 1/2-3/4" and a 2-2.5" gap,
> as long as the wine level is in the narrow "bottle-neck". The difference
> would be more significant in a wine bottle, because the air : liquid ratio
> is much greater. This is only a "seems logical" conclusion on my part. I
> have no empirical evidence to prove the theory, and I may well be incorrect.
>
> Regardless, there must be some compromise. Ideally, there would be no
> air-space, and thus no worry of oxidation or acetefication. But liquid
> expands with significant hydraulic force upon temperature increase, and some
> allowance for this must be made.
>
> I've had 3 refrigeration-system malfunctions in 2 years (and of course they
> occurred on the hottest days of the year). In each case, carboys that were
> topped up more than the levels I mentioned in my previous post either pushed
> the stopper out or burst. Those that were not, did not. Since I also use a
> layer of cling-wrap held in place with two rubber bands _over_ the stopper,
> all my wine was saved (except in the carboys which burst because the stopper
> wouldn't budge).
>
> However, if I were ill or out of town, or didn't notice the stopper had
> popped, the cling-wrap might have come off too. Had I used airlocks during
> aging, rather than solid stoppers (as some people do), the wine would have
> entered the airlock, mixed with the sterilizer, which (when the temperature
> dropped) would have contaminated the wine.
>
> Thus I have determined it best to leave such a large airspace in the
> carboy --- if I rack when the wine is at cellar temperature. If I rack when
> it is at room temperature, I would reduce the airspace by about 30%, since
> some of the thermal expansion will have already taken place. What other
> choice is there?
>
> If I had a well-insulated underground cellar, where the temperature would be
> stable even if the refrigeration system failed (assuming one was even
> needed), then I would top up to 1/2-3/4", and eliminate the (hopefully)
> small difference that the larger gap causes.
>
> How large an air-space do you use in your large tanks and barrels?