There are a couple of different types of airlock. The most common types are bubbler airlocks (on the left in the image below) and handy airlocks (on the right). Airlocks work by allowing gas to escape when the pressure builds, while not allowing any air from outside the fermentation vessel to get in.
To use both types of airlock simply follow the instructions below:
- Fill the airlock halfway with water, as shown on the image above.
- Insert the airlock into a bung or grommet at the top of your demijohn or brewing bucket.
- Leave to ferment. Once the fermentation has started you will see bubbles rising through the water.