Over the past year I’ve had great success adopting Fermware’s lined plastic buckets system for easing cleaning and ensuring that the fermentation environment is always sanitary. It’s served me well and really cut a ton of time on clean-up out. Plus I love the peace of mind of working primarily with plastic buckets rather than potentially dangerous glass carboys. However, this past fall I fermented some unpasteurized cider in some of my buckets and I believe at this point I have a wild yeast that’s migrated into a few of my bucket lids. This to several batches that used these lids becoming inadvertently infected. Because the infection seemed so inconsistent it was tough to track down, but I think at this point it’s isolated to the lids.
So, I started brain storming ideas on how to eliminate the lids and replace them with a 100% disposable solution. That’s when I ran into this Aussie Homebrewer thread about using cling wrap as a bucket lid, instead of an airlock. I have some issues in the summer time with fruit flies so whatever solution I choose needs to be able to protect against them. So, I took that original idea and I’ve come up with a hybrid system using two types of rubber bands.
Essentially what I’m doing is now using three bags per batch to guard against the beer being inadvertently exposed to the outside world (which includes the bucket itself). First I line the bucket with a fresh bag. Then I place a second bag into that liner and run off my wort into it. I aerate at run off using a vigorous run off into the fermentor to insure sufficient foam/oxygenation takes place. At this point I close the second bag and wrap it tightly with a small rubber band to hold it closed. Finally, I take a 3rd bag, place it over the top of the bucket and using a larger rubber band attach it tightly and securely to the side of the bucket.
The end result is that the beer is 100% isolated from the outside with no items which come in contact with beer being re-used from batch to batch. During fermentation the inner bag inflates and the rubber band closure is not sufficient to lock Co2 in, it inflates and then vents as pressure grows. This Co2 vents into the bag over the top of the fermentor, which in turn inflates and starts to off-gas through the larger outside rubber band as the pressure builds.
It’s not fruit fly season yet, but at this point I’d expect that the smell would start to attract them and they’re my only real concern with this setup. My hope is that the rubber band is sufficient for keeping them out. But that even if they can get past that outer rubber band, the concentration of Co2 within that outer dome would suffocate them before they could reach the beer and make it though the next rubber band closure. I guess though I just have to wait and see, I can’t find any Aussie brewers complaining about fruit flies getting through their cling wrap and rubber band airlocks. Some brewers even recommend pricking the cling wrap with a needle to help let the pressure vent!