Whether your brewing journey began ten years ago or ten days ago, you’ve had it hammered into you over and over and over: Sanitation is the single most important priority in ensuring great beer. And part of keeping things sanitary is keeping them closed to the environment. That’s why we put lids on buckets and stoppers in carboys, and it’s one reason why the airlock is designed to let gas out without letting air in.
But despite the potential risks for contamination, some brewers insist on fermenting in open containers. Open fermentation is just what it sounds like: Rather than seal everything up with an airlock in a nice carboy, bucket, or cylindroconical fermentor, you leave the top open so that the wort, and eventually beer, remains exposed to the environment.
Why on earth would you want to do this? Well, there are a few reasons.