An airlock is a simple device that allows carbon dioxide (CO2) to escape the fermenter while preventing oxygen and other contaminants from entering. The airlock is an essential part of the brewing process, as it ensures that the beer ferments properly, creating a clean and flavourful end product.
An airlock consists of a plastic or glass tube with two chambers separated by a floating lid. The top chamber is filled with water, while the bottom chamber is attached to the fermenter via a rubber stopper. During fermentation, the CO2 produced by the yeast in the fermenter rises to the top chamber of the airlock, displacing the water and creating a bubble in the water column. As the CO2 escapes through the airlock, it creates a barrier that prevents oxygen and other contaminants from entering the fermenter.
The airlock serves two primary purposes in homebrewing. First, it prevents the fermentation vessel from becoming pressurised, which can lead to a messy and potentially dangerous explosion. Second, it ensures that the beer ferments in an anaerobic environment, which is crucial for the production of flavourful and high-quality beer.
There are several types of airlocks available on the market, each with its advantages and disadvantages. The most common types of airlocks are the three-piece airlock, the S-shaped airlock, and the bubbler airlock.
The three-piece airlock is the most traditional and straightforward design. It consists of three parts – a cap, a cylindrical body, and a floating centre piece. The cylindrical body is filled with water, and the floating centre piece moves up and down as the CO2 escapes. The three-piece airlock is easy to clean and maintain, but it can be challenging to disassemble and reassemble.
The S-shaped airlock is similar to the three-piece airlock, but it has a bent tube that creates an S-shape. This design prevents the liquid in the airlock from being sucked back into the fermenter if the pressure inside the vessel drops suddenly. The S-shaped airlock is easy to use and clean, but it can be challenging to see the bubbles and determine the rate of fermentation.
The bubbler airlock is a more modern design that uses a one-way valve to allow CO2 to escape. The valve opens when the pressure inside the fermenter exceeds the pressure outside, allowing CO2 to escape. The bubbler airlock is easy to use and provides a clear visual indication of the fermentation rate, but it can be challenging to clean and maintain.
In addition to the type of airlock, the type of fermentation vessel used can also affect the effectiveness of the airlock. Fermentation vessels with a narrow neck, such as carboys, are more prone to clogging, which can prevent the airlock from functioning correctly. In contrast, fermentation vessels with wider openings, such as buckets, are less likely to clog and provide better visibility of the fermentation process.