Hi Ray

Thanks for bring light to this risk. After reading your post I placed a 12
Gal DJ for cold stabilization. I left about and inch of headspace. The
temperature in my MLF area is 70F and in the garage it is 40F. I was amazed
at how much volume contraction occurred.

I am wondering whether I should now adjust the headspace or leave it for the
3-4 weeks it will take to cold stabilize?

Joe

"Ray" > wrote in message
y.com...
> A few days ago, under a thread with the banner "Wine Aging" I made some
> comments about the effect of temperature on the ability of airlocks to
> protect wine. I promised to post more later.
>
> Air locks are designed to be a constant pressure valve to protect the
wine.
> Of course during fermentation CO2 is given off, the pressure in the vessel
> tries to go up and the excess volume bubbles out through the airlock.
> Perfect. If the temperature of bulk aging wine increases, the wine
expands,
> pressure tries to goes up, and what ever is in the head space bubbles out
> through the airlock. Fine. If the wine expands too much and all the head
> space is expelled, then wine goes out through the airlock. Not so fine.
> You can watch your wine you can prevent this.
>
> But if the temperature drops too much, a different scenario takes place.
> Outside air will bubble through the airlock into the carboy. If this
> happens it is not a very good thing. So how much protection does an
airlock
> provide and how important is this?
>
> I checked two types of airlocks. The S shaped airlock with three bubble
> chambers on each side will hold 11 cc's of liquid when properly filled.
The
> 3 piece cylindrical airlock will hold 9 cc's from bottom of the floating
> valve to where liquid spills through the tube so it provides 9 cc's of
> protection. (I did not have one of the S locks with one chamber on each
> side free to test.) For this analysis I will use the 9 cc smaller airlock
>
> The question now is how much of a temperature change will these volumes
> protect against before air bubbles through the airlock. This is effected
by
> the volume of the wine and the starting temperature. I assume 25 deg C as
> the starting temperature and determined the temperature drop the airlock
> will protect against for different size carboys. I found the following:
>
> Carboy Temp Drop
> (US gal) (deg C)
> 1 9.7
> 3 2.2
> 5 2.0
> 6 1.2
> 10 0.8
> 12 0.7
> 13 0.6
>
> This shows some pretty small numbers, but what are the restrictions of the
> calculation.
> 1) I used the expansion of water. I found the expansion table for
alcohol
> but not for 13% alcohol, so I considered water to be a better estimate. I
> suspect that wine will have more expansion and therefore less protection
but
> I can not say for certain.
> 2) I do not make a correction for expansion of the glass vessel but this
> should be very small.
> 3) This is based on temperature changes of the wine, not the room. Over
a
> one day/night temperature cycle the room may change more than the wine.
> (Thanks to Jack Keller for pointing this out.)
>
> Now what does this mean? Standard airlocks will protect carboys of 5-6
gal
> or smaller from temperature changes in a temperature controlled home and
may
> well protect the larger carboys. But if you are keeping wine in an
> unairconditioned room or in a cellar that sees temperature changes of
> several degrees C. You may want to take all this into account.
>
> You should be aware of day to night temperature changes, changes
associated
> with cold fronts, and seasonal changes. Seasonal changes, though they may
> cause the largest change will probably not be too important as there will
> only occur once a year. Day night changes may not be important as the
wine
> may not change temperature fast enough to matter. But if it does it will
be
> catastrophic as it will happen 365 times a year. Changes associated with
> cold fronts and heat waves may be the ones you really have to be concerned
> about.
>
> Ray Calvert
>
>
>