Open Fermentation

Just brewed our first AG yesterday and we are using an "open fermenter", actually, the lid is on slightly askew as to allow gas to escape. Hoping all will work out on this one, even in the dirty air of The 'Jing!:rockin:

this is my second open fermentation, very different from the first.

I just did an open fermentation with an imperial pumking clone recipe I got from this site. i got to harvest yeast during fermentation and everything went really well as far as I could tell. no contaminants got in and it was still to cold for bugs. I guess I will find out about the beer when i bottle it in a month.

this was my first open fermentation, never had much more krausen than this but it was roiling around pretty good from the CO2.

My intrepid attempt,

and again, this time with a Tripel

nice. when i see this thread i think about all of the "i opened my fermenter, is it ok?" threads.

t'would be great to include the yeast strain with your shots!

One of the many joys I've found with open fermentation is that you can actually see how different strains behave during active fermentation. Some don't produce any krausen whatsoever, and some don't seem to ever let go of it. And then there's plenty in the middle.

I did 4 four consecutive batches using a dupont saison culture recently. Starting at 68F then let free rise to 85F. No krausen at all, but fermented so vigorously you could hear the hiss of bubbles. One of the more interesting ones to open ferment, attenuates fast this way too.

Just started a new batch with WY3739 Flanders Golden Ale. First one I've done inside the fridge so far

I know its not beer but hard cider open ferment

Open fermentation should be practised with perfect timing in regards to when to bottle. When the beer stops fermenting, no CO2 is produced, therefore exposing your beer to oxygen. You can either pay close attention to the specific gravity, or if you don't feel confident in this and/or don't want to waste a lot of beer, you can replace the lid with a few days to go in the ferment. This should give you the characteristics of a beer not brewed under pressure, but with the security of CO2 to protect your brew from spoiling.

The explanation for open fermentation in the California Common style was a desire for cooler fermentation temps using the cool ambient air off the San Francisco Bay. They were trying to produce a more lager like beer without caves or refridgeration. So the cool outside air was allowed to circulate over the large shallow vessels. This produced a uniquely flavored beer "Steam Beer". I don't think wild yeast was the goal but I don't know how they prevented at least some "wild" flavors. Maybe thats one of the reasons it is considered a unique style?

Homebrewtruth said:

Open fermentation should be practised with perfect timing in regards to when to bottle. When the beer stops fermenting, no CO2 is produced, therefore exposing your beer to oxygen. You can either pay close attention to the specific gravity, or if you don't feel confident in this and/or don't want to waste a lot of beer, you can replace the lid with a few days to go in the ferment. This should give you the characteristics of a beer not brewed under pressure, but with the security of CO2 to protect your brew from spoiling.

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Agreed, timing is key. In a closed container, waiting an extra day or two to rack is not a big deal. With an open ferment, this could be a problem. You really have to rack as soon as its ready.

Its really ideal to use a top-cropping strain for this. All strains will produce some krausen, as in some foam, but only true top-croppers will actually leave a sheet of yeast cake floating on the surface. As the beer ferments, the look and texture of the krausen changes. You can tell when the beer is ready to rack by how the yeast cake on top looks. It'll go from foamy to very gummy and 'cake' looking. If you wait too long, it will drop and then you will lose the opportunity to harvest it and also put the brew at risk for oxidization or contamination.

With that said, the CO2 barrier is not the only defense. The yeast layer on top also provides some protection. A strong colony of yeast is interested in protecting its food and will out-compete other organisms when it is strong.

I always have to do a secondary with open ferments though. That perfect timing to rack is usually a couple points away from complete attenuation, and it'll need a bit more time for everything to fall out of solution including a cold crash.

When ready, I will harvest the yeast on top and immediately rack to secondary thereafter. My primaries finish in 3-4 days now. Even at fairly high gravities.

But again, in case I haven't said it enough. There are two highly important factors to successful open fermentation.

#1 - Use a strain that performs well under this condition and produces a nice yeast layer for top cropping. My favorites are:

* WLP 001 (cal ale) - this is a seriously reliable open fermenter, my fav
* Kolsch - Wyeast or White Labs - I believe most german strains are top-croppers though
* London Ale III - surprisingly, there are many english strains that are terrible for this and some that are perfect. This is a good one.
* WLP 500, WLP 530, WLP 550, WLP 575 - These Belgian strains work well

#2 - You really need a shallow vessel as a fermenter (at least a 1:1 ratio of height to diameter). Buckets are really not adequate for getting the full benefits of open fermentation. Fine for experimentation, but not for continued use. I have nothing but amazing results with this technique again and again and so much of that is due to the fermenter.

I did an open fermentation recently with a maple porter I made. I used wyeast 1968/wlp002. I dunked a sanitized cheesecloth and spread it over my bucket. Fermentation started in 8 hours after pitching. It subsided and the yeast dropped in four days. The OG was 1.065 (quite a bit higher than intended due to the unpredictably high sugar content of the syrup I used) which shows just how speedy the Fuller's strain is. It fermented at 65 degrees. After fermentation appeared to be pretty much complete, I placed a lid over the top, unsealed. One week later, I kegged it.

The results are very nice. I've used the Fuller's strain many, many times. (House strain for all non-Belgian ales) I definitely noticed an increased fruitiness, similar to the Westmalle strain (House strain for all Belgian ales) Definitely not as fruity as that, but definitely not the same neutral presence I normally get. No oxidized beer, no infection either. There is brett all over my house, if I leave a puddle of beer on the floor overnight a pellicle will have formed by the next day. Anyways, just thought I'd share. If you're thinking about trying it, I really don't think it is that risky.

I've done about 30 batches with open fermentation. Any time you are looking for strong yeast character or spicy phonolics, it definitely helps. Timing is not as critical as you might expect. I've had more issues with faulty swingtops than with open fermentation. Yes, the CO2 production drops off after fermentation slows, but CO2 is heavier than the surrounding air, so unless your fermentation area is windy, it should keep a good layer even after vigorous fermentation is complete. I usually use the krausen as a guide; once the krausen starts to drop, it's time to rack. Until then, you have not only a layer of CO2, but a layer of goo that traps the CO2 and forms a seal. Once it starts falling, I rack to a closed vessel, but I do know that it matters much, since I haven't left it for longer. I can definitely taste the difference between beer that's been exposed to air, but like I mentioned, I've noticed this more with different types of bottles than between batches. I've had one sour batch (unintended) but that came from a bad yeast wash. I think it's all about style and taste. If you're trying to craft a clean, neutral beer, open fermentation is probably not what you want. It will accelerate fermentation, accentuate esters and phenols, but probably increases risk.

Then again, so does not sanitizing for at least 2 minutes in solution, boiling for at least 20 minutes and other practices quickly shrugged ;-)