Confirmation: sometimes its just offgassing CO2

[Malty_Dog]

Just sharing an experience I had recently. Brewed up an American amber, a little high on the OG at 1.058, fermented with WLP001 California ale with 1.5L starter. Nice healthy krausen within 12 hrs, a bit of blowoff. At the two week point it had dropped to 1.012 (close to 80% attenuation) and airlock had almost completely ceased activity.

Instead of packaging (due to time constraints) went on vacation for 1 week - during which we had a heatwave at home. A/C was left on, basement probably fluctuated between 68-72 depending if the air kicked on or not. Came home and immediately checked fermenter and daggone if I didn't get a bubble in the airlock! I was surprised - and there was at least some sign of yeasty bubbles/rafts on the surface. I though - holy cow the beer is still fermenting!

Took a hydro reading and it came in at 1.012...phew! Beer was nice and clear in hydrometer...so now I believe the whole offgassing CO2 thing...

 

[WiseEyes]

Air Lock Activity Means nothing.

 

[beergolf]

 

[zachattack]

...so now I believe the whole offgassing CO2 thing...

Well it's basic science, not really something you "believe" in like religion. If you doubt science, you picked the wrong hobby!

Really though, it's always nice to convince yourself of these things.

 

[JohnSand]

Science isn't static. Brew science progresses all the time, dispelling old "scientific" notions.

 

[zachattack]

That may be true, but my point is that science is based on knowledge and experimentation and explanations. I tend to associate the word "belief" with things that can't be proven but are rather a matter of faith. Since the definition of a scientific law or principle (ex. Henry's Law) is that it simply describes the world around us, if one chooses not to "believe" in them they're basically choosing to ignore reality.

Besides, Henry's Law was formulated over 200 years ago :cross:

 

[GuldTuborg]

A belief is a statement one holds to about something that can be true or false (or could be, in theory), and is probably best considered against something like an opinion, which is alike except that it cannot (collectively) be true or false. A belief, by itself, tells you nothing of its origins or reasons for being. Or, that's what I'd argue, anyway.

Still, it's nice to have a personal experience with matters like these. It's well and good to assent to and "believe in" general laws and axioms of science, it's quite different to understand how all of them can be correctly applied in a certain situation. To suggest we can always predict a systems behavior based off currently accepted laws and models is putting the cart before the horse.

 

[zachattack]

A belief is a statement one holds to about something that can be true or false (or could be, in theory), and is probably best considered against something like an opinion, which is alike except that it cannot (collectively) be true or false. A belief, by itself, tells you nothing of its origins or reasons for being. Or, that's what I'd argue, anyway.

Still, it's nice to have a personal experience with matters like these. It's well and good to assent to and "believe in" general laws and axioms of science, it's quite different to understand how all of them can be correctly applied in a certain situation. To suggest we can always predict a systems behavior based off currently accepted laws and models is putting the cart before the horse.

Well played, sir

And I didn't mean to imply that we shouldn't continue to investigate and propose new models and theories. Especially in the area of brewing science, which as JohnSand pointed out is pretty dynamic. I was just saying that while scientists and engineers still have plenty to figure out, it seems to me that relevant principles like Henry's Law seem to be pretty well established by this point.

Sorry for the threadjack

 

[SpeedYellow]

Air Lock Activity Means nothing.

Wrong. For many many homebrewers, airlock activity is a perfectly reliable tool. Like all tools, you have to know how to use it. Apparently you don't.

 

[JonM]

Sometimes I offgas when filled with homebrew too.

 

[JeepDiver]

Wrong. For many many homebrewers, airlock activity is a perfectly reliable tool. Like all tools, you have to know how to use it. Apparently you don't.

No it is not. You can tell nothing by airlock activity other than gas is coming out. You can make some valid educated assumbtions, but on no way can you be 100% certain what is going on with the beer by airlock activity.

 

[GuldTuborg]

Well played, sir

It's all good. I was just playing a little Devil's Advocate. Plus, I think it's very easy to forget that our laws may be true, or as true as such things can be, but in any given situation it's easy to assume we know all of the relevant factors that determine what's going on, when we don't. Even when laws hold true, and we account for x and y in this situation, but forget about z, then it can throw predictions and explanations way off the mark. I think that's more what I was getting at.

Anyway, I don't mean to take this too far off course, either. Just wanted to stop in and say "cheers." If I could pass a mug your way, I would.

 

[GuldTuborg]

Sometimes I offgas when filled with homebrew too.

How can you tell? Does your airlock bubble? Come on man, you know you have to take a gravity reading in there to make sure it's not restarted fermentation!

 

[SpeedYellow]

No it is not. You can tell nothing by airlock activity other than gas is coming out. You can make some valid educated assumbtions, but on no way can you be 100% certain what is going on with the beer by airlock activity.

You don't need 100% certainly for it to be useful; what tool is 100% certain?? Different factors affect the reliability; e.g. quality of the seals, vigor of the fermentation (i.e. chance that you're just seeing off-gassing), etc. Anyone who says it means nothing is simply too lazy to explain the tool (and its limitations), or else is just blindly following the dogma.

 

[winvarin]

I agree with SpeedYellow. In and of itself, I do not count on airlock activity to indicate the end o active fermentation. I do however, adjust my temperature at different points in the active fermentation phase depending on what I want to get in terms of ester production, fermentation character, attenuation an so on.

In that regard, airlock activity and other visual cues give me a pretty good idea as to the vigor of fermentation. I can use this information to, say, determine at what point I want to begin ramping up my temp to ensure that I either dry a beer out or give the yeast a better environment for scrubbing some fermentation byproducts.

 

[SpeedYellow]

Here's an example of how you can use airlock activity. When I see 80 mL/min of CO2 coming out of the airlock on day 3-4, then it drops to very slow bubbles, I know with certainty based on my experience that it has fully fermented. Slow continued bubbles are likely meaningless.

OTOH, if CO2 output never peaked very high, then the yeast must have gotten stressed and I'd expect fermentation to take much longer, so continued bubbles may well mean something.

 

[GuldTuborg]

with certainty

Drop this phrasing, and you have a decent argument of, barring odd circumstances, how you can use airlock activity over time, combined with experience, to get a decent gauge on what's going on with your fermentation.

Interestingly, didn't you just harass someone else about the use of the word "certain" just a few posts up?

 

[JeepDiver]

Here's an example of how you can use airlock activity. When I see 80 mL/min of CO2 coming out of the airlock on day 3-4, then it drops to very slow bubbles, I know with certainty based on my experience that it has fully fermented. Slow continued bubbles are likely meaningless.

OTOH, if CO2 output never peaked very high, then the yeast must have gotten stressed and I'd expect fermentation to take much longer, so continued bubbles may well mean something.

Well im guessing if you are graphing off guessing then you probably have a conical or some other pressure cabable vessel. For the majority of people on the board using buckets or carboys that may or may not seal, im environments with not very percise temp control, looking at the bubbles in an airlock is useless. In the case of a sealed controlled environment, with closely conyrolled temps I will agree it can be useful. Though if a strong enough low pressure front comes through even your output will increase telling you nothing about fermentation.

 

[Wynne-R]

Yeah, I got into it with Revvy a while back on this very subject. It seems the issue is that anxious noobs would breathlessly write in, panicked that they weren’t seeing bubbles. The mantra arose ‘Airlock activity means nothing.”

I think what they were trying to say is more like ‘ lack of airlock activity could be a bad clue.’ You know, if your fermentor leaks like a sieve.

Nice data, yellowjacket, keep it coming. { What, speedyellow, is that even a thing? }

 

[SpeedYellow]

Drop this phrasing, and you have a decent argument of, barring odd circumstances, how you can use airlock activity over time, combined with experience, to get a decent gauge on what's going on with your fermentation...

Good catch! . I used the word "certainty" because it hasn't yet steered me wrong, but you're right, there's still the possibility, however remote, of error like with all our brewing tools and measurements.

Well im guessing if you are graphing off guessing then you probably have a conical or some other pressure cabable vessel. For the majority of people on the board using buckets or carboys that may or may not seal, im environments with not very percise temp control, looking at the bubbles in an airlock is useless...

Nah, I just use a glass carboy and orange cap. I measure CO2 with a balloon stuck on the airlock, and found the measurement to be sufficiently repeatable. Airlock bubble rate isn't accurate or repeatable for quantifying. I agree with you that controlling temps helps with this.

Yeah, I got into it with Revvy a while back on this very subject. It seems the issue is that anxious noobs would breathlessly write in, panicked that they weren’t seeing bubbles. The mantra arose ‘Airlock activity means nothing.”

I think what they were trying to say is more like ‘ lack of airlock activity could be a bad clue.’ You know, if your fermentor leaks like a sieve.

Nice data, yellowjacket, keep it coming. { What, speedyellow, is that even a thing? }

Makes sense. Oh, and speedyellow is the color of my car per the auto maker.