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Old 07-25-2013, 02:10 PM   #11
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Originally Posted by SpeedYellow View Post

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.
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Old 07-25-2013, 02:19 PM   #12
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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.
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Old 07-25-2013, 02:20 PM   #13
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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!


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Old 07-25-2013, 03:25 PM   #14
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Originally Posted by JeepDiver View Post
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.
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Old 07-26-2013, 03:13 PM   #15
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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.

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Old 07-26-2013, 03:33 PM   #16
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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.

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Old 07-26-2013, 08:25 PM   #17
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Originally Posted by SpeedYellow View Post
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?
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Old 07-26-2013, 11:59 PM   #18
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Originally Posted by SpeedYellow View Post
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.
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Old 07-27-2013, 01:04 AM   #19
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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? }

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Old 07-27-2013, 02:55 AM   #20
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Quote:
Originally Posted by GuldTuborg

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.

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Originally Posted by JeepDiver

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.

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Originally Posted by 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? }
Makes sense. Oh, and speedyellow is the color of my car per the auto maker.
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