Winemaking (rec.crafts.winemaking) Discussion of the process, recipes, tips, techniques and general exchange of lore on the process, methods and history of wine making. Includes traditional grape wines, sparkling wines & champagnes.

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Old 02-10-2003, 04:18 AM
Lum
 
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Default Air space


"Negodki" wrote in message
...
"Karen Lambert" wrote:
how much is too much air space?

snip.....
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.
snip.........


Wouldn't the amount of oxygen available is proportional to the _volume_ of
the head space, and the _rate_ of transfer to the wine would be proportional
to the surface area?
lum



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Old 02-10-2003, 05:36 AM
Negodki
 
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Default Air space

"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?


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Old 02-10-2003, 10:44 AM
Joe Sallustio
 
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Default Air space

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?

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Old 02-10-2003, 01:47 PM
Negodki
 
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Default Air space

"Joe Sallustio" wrote:

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.


If I used no cooling system, and adjusted the level with temperature
variation, retaining a 1/2" airspace, I would be doing so from dawn to dusk,
as there is a 30-50F difference in outdoor temperature, depending upon
cloud cover. This translates to about a 10-20F fluxuation indoors without
refrigeration.

It seems to me that frequent (or even infrequent) removal of the stopper to
top up or remove wine would increase the degree of oxidation. If the stopper
remains, there is a finite amount of oxidation that can occur, because there
is a finite amount of oxygen in the airspace. When you open the stopper, and
especially if you remove or disturb the wine, additional oxygen will be
introduced.

However, it is my understanding, and fervent hope, that the amount of
oxidation that will occur with that little amount of surface area exposed is
not significant. Also, isn't some small amount of oxidation required for the
aging process? Isn't this why barrels and corks are designed to "breathe" a
bit?

I suppose both concerns (oxidation and thermal expansion) could be addressed
by using a larger airspace and filling it with CO2 upon racking?


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Old 02-10-2003, 03:36 PM
Clyde Gill
 
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Default Air space




I suppose both concerns (oxidation and thermal expansion) could be

addressed
by using a larger airspace and filling it with CO2 upon racking?



CO2 will not be effective for long term storage (more than 2 or 3 days at
best). Personally, if I'm blanketing a tank, it goes no more than 24 hrs
without regassing.

I have no refrigeration, but a decent, true cellar in a full, 4 season
climate. There's still a significant amount of air transfer from
temperature fluctuations (55 to 65F), so no inert gas is going to be
effective, on it's own, without some kind of maintenance to replenish the
gas.

Not sure how to describe the headspace I leave beyond "minimum". In tanks,
depending on size/shape, that usually means about 2 inches. Think of a wine
bottle. That's about the right proportion of headspace. They are designed
to take a temperature fluctuation and minimize the exposure of gas to the
wine.


clyde




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Old 02-10-2003, 04:09 PM
Negodki
 
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Default Air space

The other thing that occurred to me is that, if one were to top up the
carboys to 1/2" when the temperature is as warm as expected, there would be
absolutely NO need to top them up when the airspace subsequently increased
due to temperature drop. There would be no more air in the larger space. It
will simply have "de-compressed", expanded to fill the space available, just
like Boyle predicted.

I wish I had a proper cellar deep in the ground.





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