An Airlock is a small device that is used during fermentation of wine or beer even cider when brewing at home. Most are made from plastic, you can get glass airlocks but these are hard to find and almost always 2nd hand. An Airlock goes on top of the demijohn, fermenter or brewing bucket. The main reason to use an Airlock is to let the carbon dioxide (CO2) out while fermenting and at the same time trying to keep air and bacteria from getting into the brew.
An Airlock is essential for brewing because as it helps keep your wine or beer free from infections or even spiders.
An Airlock creates a water barrier between the brewing vessel and the outside. As the beer or wine ferments, carbon dioxide is produced, which creates positive pressure inside the fermenter. The Airlock lets this pressure out while keeping out any unwanted air or bacteria this often can be seen by the bubbles created by the fermentation, hence the name Bubbler Airlock which is the most common airlock we sell.
After your beer or wine is in the brewing vessel, all you have to do is fill the Airlock with water or steriliser some people even use vodka, we think that's a waste of vodka. As the brew ferments, you'll see bubbles coming out of the Airlock, which is a sign that the carbon dioxide is escaping. Also it's a very good sign your brew is fermenting. If you are brewing for a long time like some wine kits can do, for 1 month or 2 its best to keep an eye on the level in the airlock and top up if needed, If air gets in the brew it could oxidise or get infected.
If you have not got an airtight seal, like with most fermenting bins, Co2 being a gas produced during fermentation of anything will just escape the easiest way possible and sometimes not though the airlock. So if you know your brew is fermenting check your lids and caps are on tight as this could be the issue.