daredevil brewing – open fermentation

In May, I watched episode 4 of Brewing TV on open fermentation. In the video, Michael Dawson brewed a Topless Hefeweizen using his standard hefe recipe, but this time he left the top off the fermenter. I was inspired to give this a shot, and I finally got around to it last Friday.

For most homebrewers, the thought of open fermentation can cause heart palpitations. After all, from the very first words we read or advice we got from veteran homebrewers puts the fear of God into you about those nasty beasties that can turn your malt nectar into a sour mess.

First, let’s differentiate between open fermentation and spontaneous fermentation. Spontaneous fermentation does not use brewer’s yeast and is left open to allow any of the wild yeast and bacteria to make a home and do the fermenting.

Open fermentation is different in that you pitch brewer’s yeast like normal, but you leave the fermenter open. The reason this works is that once the yeast start fermenting, they release carbon dioxide, which is heavier than the air we breathe.

Since it’s heavier, it stays on top of the fermenting beer and forms a protective force field over the beer, as yeast and microbes in the air need oxygen. In addition, the krauzen, the foam that forms during fermentation, also provides a protective barrier.

Sounds simple enough, but why in the world would anyone be crazy enough to risk the sanitation of their beer to leave the lid off? Well, yeast produces a lot more esters when open fermented. Fruity and spicy character becomes more pronounced. It’s a technique that’s often used with hefeweizens and Belgian beers to kick them up a notch.

First, be aware this is not intended to be the definitive guide to open fermentation. I recommend watching the Brewing TV episode to see a good demonstration. I’m going to simply share my experiences using a Sports Guy-esque running diary.

Untamed Open Fermented Tripel

For my first foray into open fermentation, I decided to do a Belgian Tripel. I’ve never brewed an all-grain Tripel before, so this is new on all fronts for me.

Brewing went as any brew normally would. The original gravity came out to 1.072. I’ll pick up the dairy with the pitching of the yeast.

Friday, September 17, 2:45 pm (0 hours)

After aerating for a half hour, I pitched one package of Wyeast Belgian Abbey 1214 into the fermenting bucket and crossed my fingers. The foam you see in the photo is not krauzen, it was left over from aerating.

I half expected the heavens to open and the yeast to sing, but nothing really happened. It’s pretty much like normal, except I’m not putting a lid on the bucket. I feel slightly crazy for doing this and wonder if I’ve just wasted an afternoon and $60.

Overall, though, I’m confident. After all, people have been doing open fermentations for centuries. It can’t be that crazy, right?

4:30 pm (2 hours)

After pitching the yeast, I went out to run some errands. As soon as I walked in the door, I could smell bread and beer. The apartment smelled like a brewery. It was glorious.

However, there isn’t any activity in the beer. I do recall that some Belgian yeast strains that I’ve used have been slow. I am not concerned, at least not yet anyway.

9:15 pm (6.5 hours)

Still nothing. I think this is the point in every brewer’s life when you have to fight the fear and resist the urge to panic. We’ve all been there. I just have to remain calm and trust the process. I just hope I can sleep.

No visible signs of fermentation

Well, off to bed. Man, I hope this works.

Saturday, September 18, 5:00 am (14 hours)


Because I am an old 33 year-old-grown-ass man, I have to get up to pee each morning around 4:30 or 5. (See, that’s what blogs are for, so people I’ve never met can learn that about me.)

I decided to check out the beer before getting back in bed, and I saw a pleasant, fluffy layer of krauzen on top. The aroma was still bread-like, with a hint of clove tossed in.

There isn’t much vigorous activity or bubbling visible. It just looks like a peaceful, puffy cloud of deliciousness.

8:30 am (17.5 hours)

Today is Brewgrass, one of the best beer festivals in the Southeast. I’ve had my ticket since February. Needless to say, I’m excited about the day ahead.

Before heading out the door, I’ve skimmed the krauzen off the top of the beer. This initial layer of foam, as you can see in the photo above, has some hops and other impurities that are helpful to remove from the beer. After removing the krauzen, new foam started to appear immediately, reforming the layer of protection.

Bowl of Krauzen

I also took a sanitized spoon and roused the yeast by gently, yet firmly, stirring from about 2/3 of the way into the bucket. From what I have heard, yeast tends to get very relaxed in an open fermented environment, so they tend to fall asleep faster than in a closed system. In order to get them to finish the work, you have to nudge them and wake them back up by stirring them back up.

Now, it’s off to Brewgrass. I’m going to miss my beer! More than 24 hours unsupervised. Now I know what it feels like to be a parent and to leave your child for the first time.

Sunday, September 19, 3:00 pm (48 hours)

Got home from Brewgrass. More on that to follow.

The beer has little foam left on it. I’d be concerned, but I’m too tired. I roused the yeast in an effort to see if I can jump start it a little more. The gravity stands at 1.014 (7.6% ABV) so I would be cool if it really didn’t ferment any more.

I’d love to see it dry out under 1.010, but I don’t think I’m getting there based on how slow the fermentation is going at this point.

7:00 pm (52 hours)

I’ve finally lost my nerve. No more foam is forming, so I’m putting the lid on it. Without a definitive protective barrier, I’m not taking any chances. I’ll come back and see how it’s doing in a couple days.

Wednesday, September 22, 7:30 pm (five days)

I took a hydrometer reading, which came in at 1.008, so I figure that fermentation should be nearly done. That’s about 8.5% ABV, which is about what I was hoping for from this batch.

I did taste the sample I took for my gravity reading and it was interesting, perhaps the most complex beer I’ve brewed. Obviously, the finished product will be different, but the flavor and aroma was pretty intense. At this point I tasted bananas, circus peanuts, black pepper and a hint of old sock.

There are no signs of infection and if all goes well I think it’s going to turn out pretty tasty once it mellows and conditions. I went ahead and racked the beer to secondary, where I will let it sit for at least another two weeks. I haven’t decided yet if I’m going to keg or bottle condition. Either way, once the beer is done, I’ll post again and let you know how it turns out.

Assuming it does turn out well, I did enjoy the process. The sights and smells over the course of fermentation enhanced the brewing experience. After all, that’s why we do this, right? To become more connected with the beer.

Don’t be scared, give it a shot.


About Brian

I like beer.
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5 Responses to daredevil brewing – open fermentation

  1. Christopher says:

    Awesome, Brian. Ballsy and awesome. I look forward to hearing how it turns out. As you point out, this is what all homebrewers are taught NOT to do. Also looking forward to your reflections on Brewgrass this year…

  2. Red says:

    That sounds awesome brother! I love your description of the taste prior to secondary :)

    Also, Double Trouble is so freaking good… we broke out one bottle to let Lindy’s parent’s try it out this past week. Phenomenal!

  3. Jim says:

    Looks amazing! Anything new on the menu soon?

  4. OD says:

    Thanx for the pictures! I got the crap scared out of me when I did an English Bitter with specialty grains. But it looks just like that!!!!

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