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-   -   Stupid Airlock (http://www.homebrewtalk.com/f14/stupid-airlock-332108/)

Wynne-R 05-30-2012 07:22 PM

Stupid Airlock
I notice a lot of people saying ďAirlock activity is meaningless.Ē Quit it, right now, youíre scaring the children. Beginners are likely to get confused when you deny them a common sense observation and try to force them into the cult of specific gravity.

Donít get me wrong, I have a hydrometer and Iím not afraid to use it, though I did go without one for a couple of years. What Iím saying is that observing airlock activity is a useful indication, as well as providing hours of entertainment watching the bubbles.

C6 H12 O6 → 2 CH3 CH2 OH + 2 CO2
glucose yields ethanol plus carbon dioxide.
This is what weíre doing, remember? My point is that the volume of CO2 indicates the speed of the reaction. Would you drive a car watching the odometer but ignoring the speedometer? Itís useful to know how fast youíre going as well as how far.

Hereís how to use this wonderful tool:

No bubbles indicates the reaction is very slow or zero. This could mean the fermentation hasnít started yet, itís stuck or done.

The interval between the bubbles is a direct indication of the volume of CO2 being produced. It could tell you youíre speeding up (more bubbles) or slowing down (fewer bubbles). In a special case, if itís spitting sanitizer, youíre way too hot.

For example, a batch I just pitched two hours ago is showing slight pressure despite it sitting on ice. This tells me there is enough activity to offset the reduced pressure of the cooling air in the headspace.

Someone is probably going to tell me thatís bad practice, but Iíve found the yeast donít mind being slowly cooled in the lag phase. Itís a big timesaver. The problem is my tap water is 25ļC (77ļF), so to cool below that requires either a bag of ice or a huge air conditioning bill. Plus I get better control with ice-water than cool air.

One more thing; people tell me they prefer the three piece airlock over the classic double bubble because itís easier to clean. Clean what? Carbonated water? The double bubble is more fun to watch and gives a more precise indication. Slainte

amandabab 05-30-2012 07:30 PM

airlock activity IS a sign of how fermentation is going.
airlock inactivity is NOT always a sign of how fermentation is going.

no bubbles can mean a lot or different things.
active bubbles can mean only one thing, activity and a properly sealed vessel.

A hydrometer is needed to get detailed information that you don't need during the ferment when you glance at a carboy.

BootstrapBill 05-30-2012 07:34 PM

That's quite a rant you have going on there. Enjoy yourself.

phoenixs4r 05-30-2012 07:39 PM

Cool story bro.

Beerthoven 05-30-2012 07:41 PM

I'm with you, Wynne. I watch the airlock to make sure fermentation has started, and then check it periodically for the first 5 days or so. I measure gravity with a hydrometer only once, after 3 weeks, to confirm the FG and ABV.

VTDuffman 05-30-2012 07:42 PM

Charles's Law says that airlock activity could indicate a raise in temperature as well. Even if fermentation has completely finished, an increase of temperature would increase the volume (and Pressure, Guy-Lussac's Law) and result in airlock activity as the CO2 in the headspace expands.

Stuff like that is why people say that airlock activity can be, but is not necessarily an indication of fermentation activity.

Revvy 05-30-2012 07:54 PM

And therefore the thousands of "children" who panic every day because their airlocks don't bubble EVEN WHEN THERE'S CONFIRMEND FERMENTATION through hydrometer readings are hallucination?

And how bout all those lager brewers who also never see, or see little or no airlock activity, because since it is cold, the gas doesn't expand enough to actually cause an airlock to bubble?

And how does an airlock that may or may not bubble, or can bubble slow, or fast or not at all, can start and stop due to changes in barometric pressure, temperature, or whether or not the cat or vacuum cleaner bumped into it, help you to know how or even if a brew is fermenting at any given time? Half the time my airlocks NEVER bubble. And sometimes the lowest gravity beer will have an airlock blowoff whereas I could be brewing a barleywine that barely bubbles?

The rate or lack of or whether or not it bubbles at all, or if it starts and stops has more relation to the environment the fermenter is in, rather than fermentation itself. All it is is a vent, a valve to let our excess gas, especially co2, nothing else. It's not a fermentation gauge whatsoever.

And the only TRULY airtight fermenters out there are if you ferment in a keg or a conical, something that can contain the pressure of fermentation.

Contrary to what you may think, neither a bucket OR a carboy with a bung is airtight. As I stated above you don't want it to be airtight, unless it's a keg or a Stainless conical, unless you like beer/ wine on your ceiling.

I've said it over and over and trolls like to try to get me, or even accuse me of lying (which I don't get why I would lie about something like this) but over the years of LOTS of batches of ALL SIZES and BOTH carboys and buckets, better bottles or glass, carboy caps or bungs, new buckets old buckets, s-types and 3 piece, I get about 50% airlock failure rate (but 100% success rate of fermentation) and it's any number if things, usually simply a non tight seal in the bucket or carboy or grommet....but to me the reason doesn't matter....the point is just trying to glance at an airlock and know what the beer is doing, just is NOT accurate.

My belief is that 1 occurrance is an anamoly, 2 may be a coincidence, BUT 3 or more occurance is an epidemic...and that's the case for folks relying on airlocks all the time, to me if 1 brewer comes on saying his airlock is not bubbling, AND he takes a reading and finds fermentation is going fine, that's an anamoly...

But DAILY on here there are at least 10 threads stating the exact thing...so MAYBE there is something to this idea that airlocks can be faulty. AND if they have the potential to be faulty, then how can we trust them to tell us what's going on?

You can quibble about it all you want, or deal in semantics, but we deal in sheer volume of users on here, and daily we have airlocks not bubbling, and many of them where a gravity reading indicates that fermentation is happening beautifully.

And yes, in an IDEAL situation (like let's say fermenting in a keg with a tight seal and no leak from around the airlock) the airlock SHOULD bubble 100% of the time (providing there's not too much headspace.) If more co2 is created than can be contained in the spavce of the fermenter, THEN an airlock should bubble....because an airlock is a valve.

But MOST of us don't have IDEAL situations, and rarely is a plastic or glass fermenter airtight- it really isn't supposed to be anyway...SO we aren't in the best situation to have IDEAL 100% accuracy of an airlock...

In other words, been there, done that, had this silly argument a million times before...and yet people STILL have fermentations that never see an blip, and folks have airlocks bubbling even after MONTHS of inactivity because of something like a change in temps...

Airlocks are vents, not fermentation gauges. And one of the most superfluous things in brewing, that new brewers seem to put the most stock in.


It your beliefs that scares the noobs, folks have actually dumped their beer because their airlock never bubbled, without ever testing it. Others have racked immediately when an airlock has stopped, and ended up with with stuck fermentation or bottle bombs, because they equate airlock stopping with fermentation ending....

Yeah you can through a lot of pretty math about how an airlock should bubble, yet every day we have a ton of people coming on who say their isn't.

Didn't people also "mathematically" prove a bumble bee is incapable of flight? ;)

Revvy 05-30-2012 07:59 PM


Originally Posted by Wynne-R (Post 4129584)
For example, a batch I just pitched two hours ago is showing slight pressure despite it sitting on ice. This tells me there is enough activity to offset the reduced pressure of the cooling air in the headspace.

No actually you still have Oxygen trapped in the headspace. If you pitched two hours ago, it's really doubtful your yeast has started converting sugar to co2.

If you [possibly do have some co2 developing that AND the oxygen in there is why you feel "pressure" from pressing the lid.

But most of the time, on day one, even if an airlock bubbles, it's NOT due to co2 being produced and fermentation starting yet, [i]but simple off gassing of whatever is in the headspace (usually just O2.)

You oxygented your wort, and you also snapped your lid or bung down, pushing more oxygen into the headspace, hence the pressure.

Like I said, been there, done that....Seen this "argument" as well. ;)

homebrewdad 05-30-2012 08:13 PM

Bubbles are cool, bubbles are fun. If you see rapid bubbles in the first couple of days after you pitch, you do know that fermentation is going well.

We get a dozen posts a day from those that don't see bubbles, but it almost always comes from a lack of an airtight seal. Would you have us tell those newbies to freak out, caulk up all of their seals, and THEN see if they have bubbles?

Better to tell them that a lack of bubbling is no big deal, that the beer is likely doing just fine. Leave it alone a couple of weeks, then pull a gravity reading.

Don't go open up the bucket a half dozen times and create repeated contamination risks - just leave the yeast alone and let it make beer. It knows how to do so. It does not need your help or bubble approval.

TopherM 05-30-2012 08:28 PM

I agree with Revy 100%. The airlock is a GUIDE, but it certainly isn't anywhere close to a scientific instrument.

I think the point Revy makes throughout all of his posts on this subject, and the point that the OP misses after his rant is that at the BASIC level, all brewers need to know the TRUE FOUNDATIONS - the what, when, why, and how - of fermentation to really know what's going on and be able to properly and consistently manipulate the active variables. The only way to really understand the foundations of fermentation is looking at it scientifically, which always means HYDROMETER READINGS.

I believe once you have the basic concepts of fermentation down, then a hydrometer becomes quite optional, but for a newbie you just can't run around teaching them that an airlock is a replacement for a hydrometer - you are doing them a diservice and not teaching them the basic foundations they really need to be consistently successful!

So is airlock activity meaningless? No, it says alot to someone who knows exactly what's going on in that fermentor, but those who DO NOT know exactly what's going on in the first place need to learn that first!

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