Help! Airlock pressure is reversed

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Adrian Rovito

Apr 3, 2023
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Hi, first time I'm making wine. The wine was first put into Demijohns about a month ago, in that time I've racked twice to clean the lees (the most recent rack was a week ago)

I have two 54L Demijohns that are both about 85% full, sitting right next to each other but just one of them has the pressure in the airlock reversed, as if its sucking in air (see attached photo - ignore the ghetto straps needed to stop bung slip). Through googling all I can find is it being caused by change in the wine temp. Weird though because both Demijohns are literally next to each other, even though it is admittedly getting colder now that winter is getting closer in Australia.

What I cant find online is what I do about this, is it a problem? What can I do to fix it? Should I be waiting to see if it corrects? or does it require immediate action?


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No immediate action required. Although I suggest you invest in a new airlock, it looks like it’s been stored in your mechanics toolbox for 3 decades!

The reverse action is probably temperature/pressure changes due to weather. No worries.

You say 85% full? They really should be as full as possible, no more than 50mm (edit) or 2”. Use any wine to top off to full. The excessive airspace will increase the risk of your wine oxidizing.
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Air space WILL cause oxidation of your wine. Consider filling one demijohn full and moving the residual wine to another smaller carboy. OR. Consider flushing with argon OR putting the small portion in a wine bag OR Consider using -20 inches Hg vacuum and a check valve BUT this risks breaking the demijohn.
It is normal to have volume changes as liquids or gasses cool. It is normal to have old corks get cracked and leak gas, or to have a burr where the airlock was molded and leak air or even a little dirt on the glass could cause leakage.
All good suggestions here. I would definitely get some new airlocks (ones with caps). It sounds like you have something near 96 liters of wine. I suggest filling one of the 54 liter demijohns and get two 5 gallon (19 liter) carboys for the remainder. That should fill the containers adequately.
The wine was first put into Demijohns about a month ago, in that time I've racked twice to clean the lees (the most recent rack was a week ago)
In the past the mandate was to rack the wine off the lees repeatedly until this is none, and rack every 3 months during bulk aging.

Don't do this. You want to rack only when you're gaining something from it. It appears you're researching things, which is great. Read about the differences between gross lees (fruit solids) and fine lees (yeast hulls), and sur lie and battonage. Wine can rest on fine lees indefinitely; there's no pressing need to rack off it.

Also, in my sig is a link for MoreWine! Manuals -- skim the White Wine manual. It's too much to read intently, so skim it, then skim it again, so you have a better grasp on the winemaking process.

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