Specialized Homebrewing Equipment: Your Fermentation Lock

A fermentation lock protects your beer from contamination by letting the carbon dioxide gas out of the fermener but not allowing air into the fermenter. Water or alcohol is added to the outer part of the lock to form a liquid barrier. I use vodka rather than water to maintain a more sterile environment.

The fermentation progress can be watched as the carbon dioxide released by fermentation bubbles through the water (vodka). Fermentation is essentially complete once the bubbling has slowed to one bubble every 2 or 3 minutes. This can be within 2 or 3 days or can take more than a week. Some very slowly fermenting beverages such as mead (see Papazian's book) can take months to ferment completely.