Not because it doesn't work etc, because yes it does. I use a lid and airlock because I'm lazy as hell, inasfaras, I just use hot water into a sanitised bucket with the sugar to the target volume (generally 25 litres), I use a leccy balloon whisk or immersion blender to spin the hell out of it and dissolve the sugar which has the side effect of incorporating some air/O2, then seal the lid on and add an airlock
The lid and lock are just to stop possible bacterial contaminants while it's cooling down.
The next day, I just pitch the yeast into the cooled wash and give it about 2 or 3 minutes with the whisk or blender as above, then re-seal and airlock.
The first of the gas out of the lock will be any trapped air/O2 as the CO2 is lighter, then after a few minutes of bubbling the bucket void (about 4 inches with my buckets) will be full of CO2 so no issue.
loose lids can help to keep out dust and flies.
As Mash points out, if the wash has some sort of bits in it already (grapes or other fruits for wines, maybe grain for wort etc), then it's not unusual to get some "cap" rising up on top of a layer of trapped gaseous release - if it blocks the airlock, then it can get very messy.
Oh, and while using a specific yeast, it generally forms into a colony big enough to swamp any wild yeast that may get in, using the lid and lock also helps maintain consistent results, that you don't get when doing open ferments - as it could be many different wild strains that take hold.
The airspace thing can become an issue after the ferment, so you rack off the lees and find that with the racking losses, you need to use something as an anti-oxidant, as it's the oxygen in air that can degrade some "wines". The most frequently encountered anti-oxidant will be campden tablets a.k.a. sulphites. Some even go as far as using bottles of compressed gas to force out any air/O2 and its accompanying passengers (wild yeast, bacteria etc)........Statistics: Posted by Phantom — Sun May 20, 2018 9:58 am
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