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Old 06-27-2012, 06:17 AM   #1
Apr 2012
Berkeley, CA
Posts: 175
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I have a really simple question. Do we really need to use an airlock on beer during fermentation?

I see how it makes sense if you are going to age or condition something like wine or mead where you don't want to expose it to oxygen and you need to keep it around for months to years.

If I am brewing a batch of beer usually I will just use a primary (carboy or bucket). I will leave it in there for around 2 weeks. By the end of the first week fermentation is usually done fermenting. I then use the next week to "condition" the beer and/or dry hop it. I then bottle.

What I have in mind would be just placing some sanitized aluminum foil over the opening. It seems to me that the foil should keep out dust, preventing it from getting contaminated. There should be a CO2 blanket inside the carboy, protecting the beer from oxygen.

If any oxygen gets to the beer, maybe when I bottle carbonate the oxygen will get scrubbed out by the yeast? This wouldn't work if I force carbonated. (I'm not sure if the yeast in the bottle actually would scrub out oxygen but it seems like they would).

I guess I have two major questions:
1) Is it crazy to not use an airlock? Why? Does anybody not use airlocks?
2) If I don't use an airlock, how long can I leave the beer in the carboy?

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Old 06-27-2012, 06:31 AM   #2
Schnitzengiggle's Avatar
Feb 2009
Tucson, AZ
Posts: 2,560
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Blow-off hose for the first week, and airlock for the following weeks. Airlocks are a simple device that nearly ensures no contaminants will fall into your beer (given you keep it full of liquid), and it will also prevent oxygenation from occurring by not allowing the co2 to escape/be blown out by any means.

Absolutely necessary? probably not... Do you think that the ancients used airlocks, probably first anyway...

However, airlocks have come into use for a reason, so to question the use of airlocks as if they are completely unnecessary, even for shorter fermentations, is folly. Again, required, no. Recommended, helpful, and cheap insurance...absolutely.

Spend the $0.89 and put an airlock on your vessel.
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Old 06-27-2012, 08:41 AM   #3
Jun 2010
Posts: 930
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My fermentation chamber will only fit 2 fermenters if one is on the hump, an airlock will not fit in. I typically let it ferment without an airlock, and I have had nothing bad happen.

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Old 06-27-2012, 08:55 AM   #4
Jul 2011
Richardson, Texas
Posts: 1,025
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I never use an airlock. When I use a bucket, I just set the lid on loosely. Some of my buckets have already been butchered with an airlock hole, so I set something over the hole like the lid of a gallon water jug. If I use a carboy, I either put aluminum foil over the top, or I use an orange carboy cap and just leave one of the openings open.

It is not necessary to ferment beer in a closed container, unless you are trying to ferment under pressure like many commercial breweries do. There are many breweries in Europe that ferment in open vessels. Giant, huge open vessels.

My theory is that homebrewers started using airlocks because they copied from wine making, where the wine sits around for months aging. That's probably also the reason they started using carboys, which in my opinion are not very suited at all to beer brewing.

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Old 06-27-2012, 09:22 AM   #5
May 2012
Inglewood, Ca
Posts: 199
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During active fermentation I see no need to have an airlock especially if the opening isn't too big. There will be a steady stream of co2 out of the vessel that any entering oxygen will probably end up going right back out. And the co2 blanket idea would only work if it was heavier than air, like Argon. Like mentioned before the importance comes after the active parts of the fermentation when there isn't that steady stream of co2 out of your batch.

I tried an open fermentation experiment basically pouring wort into a used smack pack, it did end up fermenting however it did attract fruit flies... A lot, and then they would die in the container. Those open breweries in Europe are either in a controlled environment or in centuries old tried and true locations known for open fermentation. The results will be highly dependent on the flora and fauna of your given fermentation environment, when you "throw it to the wolves" per say. Every home brewery is unique so I'm assuming they teach new home brewers to err on the side of caution and spend the $0.89 on an airlock to avoid people regretting buying a couple buckets and an extract kit, what I like to call the "Mr. Beer effect"

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Old 06-27-2012, 02:59 PM   #6
ChuckO's Avatar
Oct 2008
Keyrock, WV
Posts: 1,028
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My first beer kit suggested fermenting in a white plastic waste bin with a piece of cheesecloth placed over it. One week in there and then racked into a 5 gal. carboy. Everything turned out well and produced good beer.

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Old 06-27-2012, 03:11 PM   #7
Nov 2010
Bay Area, CA
Posts: 148
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You have two factors in your favor during the early, active phase of fermentation. First, while the sugar concentration is high, yeast will ferment even in the presence of oxygen (this is called the Crabtree effect). Second, unless you agitate, the wort is under a blanket of CO2, and so is more or less anaerobic anyway.

But as the sugar gets used up, if oxygen is present the yeast will gradually switch from fermentation to respiration, using up the alcohol as fuel. You're no longer pumping out CO2 at a huge rate, so you can no longer rely on your CO2 blanket keeping conditions anaerobic.

Bottom line, if you bottle/keg quickly after active fermentation slows (and can keep the fruit flies away), you're probably OK with an open system. But if you rack to a secondary, or keep it in the primary after the gravity drops, you'll want to use an airlock. I don't know at what gravity the Crabtree effect goes away, but I wouldn't let it drop much below 1.020 before slapping on the airlock.

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Old 06-27-2012, 03:26 PM   #8
sweetcell's Avatar
Jan 2012
Rockville, MD
Posts: 5,192
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air-locks not needed. someone here posted about brewers in the middle east that used rubber ballons: poke a pin-hole to let the excess CO2 slowly escape, or just manually release pressure every now and then when the ballon fills up (wouldn't work at the peak of fermentation since a ballon probably is filled every minute or so).

a sanitized piece of foil, or a few layers of saran-wrap, would work just fine. just make sure the CO2 has some way out (which is pretty much automatic if you use foil - the crinkles along the edge will create small gaps for the gas to escape through).

but for less than a dollar i don't see why you wouldn't use an airlock. they sound so pretty

Originally Posted by HopOnHops View Post
And the co2 blanket idea would only work if it was heavier than air, like Argon.
CO2 is heavier than air (mostly N and O2), FYI.
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Old 06-27-2012, 03:27 PM   #9
Apr 2012
Berkeley, CA
Posts: 175
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Thanks for everybody who responded. I can't fit the airlock where I am going to put my carboy because it would be too tall so I'm going to try to use some firmly fitting foil. This should keep out all the dust, bugs, etc.

Also, CO2 is 15% denser than air however not as dense as argon which is 38% denser.

Later today I'm going to actually calculate how much a standard airlock slows down oxygen diffusion and compare it to aluminum foil covered.

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Old 06-27-2012, 03:39 PM   #10
jetmac's Avatar
Aug 2010
Mcdonough, Ga
Posts: 1,140
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I use something i think is called a "dry lock"

It's like a stopper made from silicon. It has 4 holes going through it from top to bottom with an intergrated "flapper" on top. Works great in my compact fridge where a traditional air lock won't fit.

I can't remember off hand where I got it.
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Revvy>>You shouldn't worry about ANYTHING, you didn't hurt the yeast, they know what they need to do, they want to eat all that sugar they are swimming around in. They want to pee alcohol and fart co2, it's their nature.

Bobby_M>>I flood the keg with CO2 for one minute with the lid off, rack the beer in to the bottom gently, seal it, flood it, vent it. If there's still O2 in there after that, F it.

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