Things sometimes go wrong as we all know and most of the time I’ve found that beer is very forgiving. This happened this past week.
I brewed a couple of batches, a porter and a blonde. The porter was first. I always go back the next day to make sure the yeast is active and getting the job done. I’ve never had a huge issue with the krausen going all the way to the blow off tube into the starsan in the jar, but this time the blow off tube had jumped out of the jar and it was a nice puddle of wort on top of the table. Cleaned it up, and clipped the blow off tube so it wouldn’t jump out of the jar again and let it continue. So far everything is looking good.
In a couple of days, I brewed a blond. Brew day went very well. Go back the next day every thing looked ok, yeast was working, but not going overboard. The next morning I go to check on the the brews and the blow off tube on the blond had blown completely out of the top of the fermenter. I’d never had that happen before. Not a huge mess, but some cleaning was required.
What I was worried about was the oxygen getting into the beer. I put a fresh and clean airlock on it and have had to change it out a couple of times due to blow off getting in it.
From an oxygen standpoint, I wouldn’t be too super worried given that the exposure was during the most active part of fermentation–I suspect the carbon dioxide from the beer would mitigate any oxygen exposure. In practice, it’s probably not much different from open fermentation used in some styles of brewing (e.g., saisons). I strongly suspect you’ll be fine!
Oxygen is important for yeast health. When it’s in active fermentation it will scavenge O2 and become more robust. I have even boosted a high gravity beer with O2 24 hours after pitching the yeast.
Oxygen becomes a problem after that noticeable activity slows down. Basically, when the yeast is in it’s growth phase, O2 makes it happier.
Another possible scare, is a bacterial infection finding it’s way in there. I wouldn’t be too concerned - because you put a lot of yeast in there and it’s a fungus. What ever little bit of bacteria that could find it’s way in there, it won’t be able to outcompete the yeast.
So not only do I think it will survive, it looks like it’s thriving!
If fermentation was still active, it’s fine. The “CO2 blanket” is real as long as CO2 is being actively created by fermentation. When fermentation subsides, that protection mostly stops, although there is still a small, minor, outgassing, but not enough to prevent gas mixing.
Side note: This is why stir plates are completely useless for starters. Think you’re oxygenating that starter? No, you’re not. You’re just off-gassing the CO2 faster.
I have actually watched a lager fermentation in an open vessel and the brewmaster took his arm and wiped off the Krausen from the top and kept on going. C02 will keep a blanket of it above the beer to prevent nasties. It has worked for years in German lager brewing and other types of beers. I wouldn’t worry.
Most people don;t realize that CO2 is heavier than air and will naturally form a blanket. So no worries about oxygen at all until your krausen crashes.
As far as preventing the airlock projectiles, it is all about carboy fill levels and proteins/yeast chunks that clog the airlock/blow-off tube. For every batch, don’t overfill your fermenters. Also make sure you prevent excess trub and hot break from getting into your primary after chilling. Another nice little trick, depending on the equipment you use, is to skim off excess protein when you are first bringing your wort to a boil. Just before you add your first hops, remove the excess protein chunks that are floating. This raft of excess protein can reduce hop isomerization rates and only winds up as hot break later on. If you are able to skim it off while you’re waiting for the boil, it’s less waste later.