Encountering Old Problems (or, How I Dealt With Two Blowoffs in a Row After Nearly 3 Years Without Needing One)

It is a common occurrence for the novice homebrewer. You boil your wort, add some hops, and chill it down to a pitchable temperature, then you add your yeast and check up the next day after work, to see if the fermentation has started... only to find that the beer has fermented so aggressively that yeast and beer are literally shooting out of the airlock and all over your closet. Sometimes the ferment is so great that the airlock and rubber stopper are sitting on the floor while a bubbly mess of muddy-looking yeast is spewing out of your carboy like some horrible Irish volcano.

This is called a blowoff, and it is a relatively avoidable problem. Blowoffs are caused by an active fermentation, as the CO2 produced by the yeast attempts to come out of solution by bubbling out the fermenting beer. This foamy yeast layer on the top of the beer is called krausen, and it is normally a sign of a healthy ferment. The more sugar and protein in the wort, the bigger and foamier the krausen will be. High pitching rates, warmer fermentation temperatures and certain yeast strains have also been known to cause foamier, messier krausen. As long as you are fermenting at your desired temperature with the correct amount of the proper yeast strain, the size of the krausen will not affect the beer. The trick is keeping the beer (and accompanying yeast) in the fermenter and out of the airlock.

The first time I experienced a blowoff was when I brewed my second homebrew after having taken a year-long break from the hobby (when I lived in NYC, I didn't have the space or the proper equipment to brew anything more complicated than a french press coffee). The year was 2008, I was living alone in a new city (Portland, OR), and I was spending a lot of time on homebrewing forums like Northern Brewer's Forum because I hadn't made many friends. I read about this technique called "reusing yeast" which took the yeast from the bottom of the fermenter and used it to make a fresh batch of beer. I had no idea how much I would utilize this technique in the future, but boy did I do it wrong the first time.

I proceeded to pour the fresh 72º wort from my ~1.070 chocolate stout directly on top of the full yeast cake left by my ~1.058 Amber Ale, which had just been racked to secondary. I let that stout it ferment at ambient, which was a pretty tame 58º F. Then I went out that night (because it was Halloween), came back home and cranked the heat up to 70º (because I had guests spending the night), and checked how the beer was doing the following morning. I found the airlock on the floor, a yeasty mess on the carpet, more yeast on the walls, and a sufficiently disgusting carboy. I then decided to use a blowoff to control the mess (basically a PVC tube going from the airlock hole directly into a 750L bottle filled with sanitizer and water). The next day the bottle was overflowing and making more of a mess. I then used a big 1 gal jug, which worked just fine.

Later I learned that the only guarantee to needing a blowoff is small headspace + high gravity wort + high protein grain bill + giant yeast pitch + warm fermentation temperature. I had several more blowoffs over the years, one even occurring in secondary (I guess fermentation picked back up when I racked to secondary). I would even plan for blowoffs whenever I would brew a high-gravity beer or I would leave less than 25% of the fermenter for headspace. But once I started controlling fermentation temperatures, I noticed something. When I fermented cooler (≤62º F), I wouldn't ever need a blowoff. The ferments lasted longer, but they never got out of control. And the beers ended up cleaner, too (even with "estery" English yeasts). So I started fermenting nearly everything ~2º under the recommended minimum listed on the wyeast/white labs/fermentis/danstar website. It worked. My beers improved and the messes were minimized.

Then something else happened: I stopped brewing high-gravity and high protein beers. My DIPA's got replaced by India Session Ales and APA's. My ESB's were replaced by Best Bitters. My Porter shrunk from its original 1.066 OG to a mere 1.052. I stopped brewing witbiers and Dubbels. My stouts were no longer Imperial. And my liver was thankful. No doubt this was in response to the Imperial-everything trend, and the fact that I found a nice IPA easier and easier to buy (and a fine session ale increasingly difficult to locate). But then I started brewing with someone else, and we started to retread the old trend of bigger, bolder beers. Our first co-brew was a big West Coast IPA, followed by a Rye APA, then we went on to do a Tripel, followed by a 1.062 version of my Grey Skies Porter, and not long after that, we did an Imperial Stout.

It was inevitable. I was going to brew up another blowoff. It was the Imperial Stout that did it. My kettle was filled almost to the brim with high gravity wort, and I pitched a tremendous amount of fresh yeast slurry. The blowoff started less than 8 hours after pitching the yeast. I had to build a blowoff for the first time since 2010. It was balls.

My very next brew was one I had been planning for a long time - I wanted to do a Black IPA with sinamar as the sole "roast" agent. But I ended up somehow putting nearly a gallon more wort in my fermenter than I typically do. Somehow I had boiled off 40% less than expected fascinating, I know. I proceeded to pitch about a pint of thick, hoppy slurry I got from Reuben at Triple Rock. So what happened? More blowoff. This time fermentation began within 8 hours of pitching (wort was 60º F when I pitched the yeast, and the fermentation chamber was set to 56º F). One hour after I noticed fermentation began, I found it had begun to blowoff. I quickly built a new blowoff setup and went on my merry way.

So the lesson in all of this? Yeast is alive and humans are forgetful. Try to remember that, just because you haven't had a brewing mishap for a while doesn't mean you'll never have it again.