Brewing Airlocks

What Is An Airlock?

An airlock is a piece of homebrewing equipment filled with sanitizer that prevents oxygen and bacteria from contaminating your fermenting beer. It allows CO2 to escape the fermentation vessel but will not allow in contaminants. The airlock is mounted on the top of your fermenter via a rubber bung or a ported lid.

Airlock History

The concept of the airlock dates back to the 19th Century when Louis Pasteur invented the swan-neck flask and discovered it prevented bacteria from contaminating the liquid contained within the flask. This later led to the discovery of pasteurization. Homebrewers have a lot to thank Louis Pasteur for, including the discovery of yeast that is used for brewing.

Airlock Styles

There are a couple of different airlock styles commonly used in homebrewing such as the single-piece or bubbler airlock, and the 3-piece airlock. However, there are also thrifty hacks, a blow-off tube, or even a common balloon.

3-Piece Airlock - This is one of the most popular airlocks, it’s easily taken apart, cleaned, and sanitized before and after fermentation. Unlike the bubbler, this airlock has the potential of getting contaminants in your beer if you're moving or shaking the fermenter. However, with the airlock filled with sanitizer and being handled carefully the risk is very low.

Single-Piece AKA Bubbler Airlock -  This is the classic airlock used by homebrewers. It’s the most effective airlock for keeping contaminants out of your beer. However, if your fermenter doesn’t have enough headspace for the krausen, the krausen can plug up your bubbler, potentially leading to a big mess. The Bubbler Airlock also provides the added benefit of allowing you to visually monitor the status of fermentation activity. By monitoring the liquid level in the two chambers of the airlock you can roughly judge overall fermentation activity. When the liquid is at an equal level in each airlock chamber CO2 release is subsiding, meaning that primary fermentation is coming to an end.

Blow-Off Tubing - The blowoff method is often used when there is insufficient headspace in your fermenter. Insert one end of a sanitized tube into the mouth of your carboy or a ported lid like the lid used by the Big Mouth Bubbler. Insert the other end of the tube into a bucket of sanitized water. You won’t need to fill the bucket to the top because the blow-off could spill over the sides of the bucket. You will, however, want to make sure the tube is submerged in the sanitized water. By submerging the end of the tube you have in effect created a large airlock. It will allow CO2 to escape, but keep wild yeast and bacteria from getting in.

Airlock Hacks - If you’re the epitome of the frugal homebrewer you might want to try a balloon. Wrap a balloon over the mouth of your carboy and perforate the balloon with a few small holes to release the CO2. These holes would be small enough to keep out potential beer infectors.