Wines and SpiritsHome Winemaking - Airlocks - Don't Keep Them Full!
Airlocks are a vital part of the home winemaker"s equipment. Fitting into a bung or rubber stopper that is used as a closure for the carboy (secondary fermenter), an airlock should allow carbon dioxide gas to escape while keeping air out. Many new winemakers don"t seem to know exactly what do with an airlock.
I"ve seen two wrong ways of using the cylinder shaped airlocks:
1. An Empty Airlock
An airlock needs to have liquid in it in order to stop air from entering into the carboy and possibly contaminating the wine. An empty airlock, while allowing carbon dioxide gas to escape, is offering zero protection to the wine as air and bacteria can get in. The liquids that are commonly used include plain water, a potassium metabisulfite and water solution, or vodka.
2. A Full Airlock
While a full airlock will offer protection against air getting into the wine, it does not allow carbon dioxide gas to escape. Indeed, while a fermentation is going on, if the airlock is overfilled, the carbon dioxide gas building up in the carboy will cause the rubber bung or stopper to blow out of the opening of the carboy - and you"ve just lost your protection from air and other contaminants.
The Correct Way:
So how full is "full enough" when using standard cylinder type airlocks? If you look closely at the large cylinder portion (not the tube that is inserted into the bung or stopper), you will see a line about half way between the top and bottom. You should fill the airlock to this line before inserting the internal plastic dome. Then, snap the dust cover over the top.
Doing it the correct way will protect your homemade wine while allowing carbon dioxide to escape. Even over filling too much beyond the line on the airlock can slow down the degassing process.