• We have a new forum and it needs your help! Homebrewing Deals is a forum to post whatever deals and specials you find that other homebrewers might value! Includes coupon layering, Craigslist finds, eBay finds, Amazon specials, etc.

Airlock really needed?

HomeBrewTalk.com - Beer, Wine, Mead, & Cider Brewing Discussion Community.

Help Support Homebrew Talk:

DrHop

Well-Known Member
Joined
Apr 14, 2012
Messages
175
Reaction score
11
Location
Berkeley
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?
 

Schnitzengiggle

Well-Known Member
Joined
Feb 19, 2009
Messages
2,560
Reaction score
36
Location
Tucson
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 not...at 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.
 

cfonnes

Well-Known Member
Joined
Jun 21, 2010
Messages
930
Reaction score
65
Location
Utah
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.
 

BetterSense

Well-Known Member
Joined
Jul 17, 2011
Messages
1,025
Reaction score
58
Location
Richardson
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.
 

HopOnHops

Well-Known Member
Joined
May 23, 2012
Messages
200
Reaction score
7
Location
Inglewood
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"
 

ChuckO

Well-Known Member
Lifetime Supporter
Joined
Oct 14, 2008
Messages
1,035
Reaction score
159
Location
Keyrock
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.
 

corax

Supporting Member
HBT Supporter
Joined
Nov 27, 2010
Messages
310
Reaction score
132
Location
California Central Valley
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.
 

sweetcell

Protruding Member
HBT Supporter
Joined
Jan 15, 2012
Messages
5,452
Reaction score
1,215
Location
North Bend, WA
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 :ban:

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.
 
OP
D

DrHop

Well-Known Member
Joined
Apr 14, 2012
Messages
175
Reaction score
11
Location
Berkeley
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.
 

jetmac

Supporting Member
HBT Supporter
Joined
Aug 16, 2010
Messages
1,111
Reaction score
38
Location
Mcdonough
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.
 

Clark2012

Member
Joined
Jun 26, 2012
Messages
8
Reaction score
0
Location
San Francisco
Airlocks are an important tool to (1) prevent contamination from undesired microorganisms, (2) to reduce oxidation (oxidized beer tastes stale at least, some say like cardboard or worse). Further yet, (3) airlocks are useful as a gauge that allows you to measure how much fermentation is taking place (i.e. how many bubbles per minute). I find it's best to use the three-piece bubbler on "primary" fermentations and the one-piece airlock on "secondary" fermentations serves as a good "pressure guage" that allows you to literally see the pressure in your fermentation vessel. Both cost under a dollar, as noted by many others here. (A good BTW: buckets are easier to clean, but I choose to ferment only in glass because my Dad (a winemaker) tells me that alcohol is capable of dissolving the plastic to some degree (which is carcinogenic).)

I've never made vinegar, but my understanding it that the risk of accidentally making acetic acid, or "malt vinegar", in this case, is much higher when your brew is exposed to oxygen. That's precisely how vinegar is made - the fermented liquids are exposed to air and some sort of acetic-acid- producing bacteria, which can be airborne!

The thought of not using an airlock seems risky - why risk contamination from undesired microorganisms (bacteria, mold, possibly wild yeast), oxidation, and possible vinegar-making?
 

helibrewer

Well-Known Member
Joined
Nov 11, 2011
Messages
4,121
Reaction score
471
Location
Wilmington
Once fermentation is complete I replace the airlock with a rubber stopper and age for 30 days cold, pails are a PITA to move around with an airlock on them and once the "vent" is no longer required, there's no need to have it there. A stopper precents all the same things from entering your vessel as an airlock. As long as you don't remove the lid, the CO2 blanket will remain intact. If I need to remove the lid, I just lay down another blanket of CO2 abd replace the lid.

The self-venting silicone bungs used in winemaking are excellent replacements for airlocks and much lower profile.
 

Homercidal

Licensed Sensual Massage Therapist.
Lifetime Supporter
Joined
Feb 10, 2008
Messages
33,324
Reaction score
5,801
Location
Reed City, MI
While not absolutely necessary during initial fermentation, the risks outweigh the cost IMO. Bugs are a main reason not to skip it. Other things that might fall in count as well. Considering the cost of most other equipment and ingredients, it's practically free.

Obviously your situation seems to preclude you using an airlock and if you cover with plastic wrap or foil and allow the gas to escape, you should be good to go. I had a design for a ferm chamber that also had almost no clearance for an airlock and my design solution was to build an "S" shaped adapter that would be inserted into the bung or lid, and would run across the lid, then down and over and back up again so that the top of the airlock was even or lower than the lid.

I also like the flapper idea. As long as the krausen and gunk that spews forth doesn't get too infected and pass into the beer, that should work great and be low profile.

Another idea is to get one of those bacteria proof filters and plug it into a piece of tubing that runs from the lid and then down. No airlock needed as the CO2 should be passing OUT and even if some air were to get back in, it would be bacteria free.
 
OP
D

DrHop

Well-Known Member
Joined
Apr 14, 2012
Messages
175
Reaction score
11
Location
Berkeley
I think I'm gonna stick with my foil on this batch but I'll probably use a blow off tube in the future since it doesn't take up as much vertical space. I still do think that the airlock is not completely necessarily. I have a bucket with a lid that leaks (I never have gotten bubbles through the airlock) and I've made many batches of beer with that bucket without a problem. I think as long as somebody is sticking to a short fermentation regime (maybe 2-4 weeks) I bet the airlocks are complete overkill however they probably do make sense for something like a barleywine where you'd keep in in the carboy for months.

I crunched some numbers (I'm a engineer and nerd...). Here are the rates of oxygen diffusion if you assume that there is no oxygen inside the carboy (roughly correct and shouldn't affect the numbers much):
Airlock with water = 0.038 mg/day
Airlock with vodka = 0.052 mg/day
Aluminum foil = 10.9 mg/day (I assumed you can get the aluminum foil pressed down good so that there was a 1 micron gap between the glass and foil. The rate will be linear with the gap thickness so you can just scale it up if you think there is a larger gap.)

This basically says that airlocks are a lot better at preventing oxygen from entering (~280 times better). That said, both numbers are very low. This calculation basically assumes I have a carboy full of CO2 and there is no CO2 production as time goes on. If you have any flowrate of CO2 going out of your vessel from fermentation, these oxygen diffusion rates will basically drop to zero.

The funny thing is if you use a plastic bucket (HDPE) then you have a diffusion rate of ~15.8 mg/day of oxygen through the walls of the bucket so it doesn't really matter what you put on the top.

Conclusions:

1)Use glass carboys with an airlock if you want to age something for a long time (if you think 10's of mg/day of oxygen exposure is harmful). It seems to me that racking to a secondary is probably a billion times (did not calculate this) more oxygen exposure than what you'd get through any of these oxygen diffusion pathways.

2)Since plastic buckets make great batches of beer just like glass carboys (for month long brews), I'd say that it probably doesn't matter.

3)Of course you want to keep out airborne stuff from getting in your beer. This requires covering any opening with a barrier however I still don't think an airlock is required.

4)Airlocks and blowoff tubes are super cheap and easy to use so I agree they make a lot of sense to use.
 
OP
D

DrHop

Well-Known Member
Joined
Apr 14, 2012
Messages
175
Reaction score
11
Location
Berkeley
Just to add to the last post, a diffusion rate of 10 mg/day equates to around 0.5 ppm increase in O2 concentration if you have a 5 gallon batch of beer.

I am a little surprised that it is so high because typically oxygenated wort is ~10 ppm O2 and after fermentation is over the O2 concentration should be down to ~0.5 ppm.

My numbers I put in the post before I believe should be correct because it's a pretty straightforward diffusion problem but they seem to be higher than I would think or the yeast post-fermentation does a pretty good job of scrubbing any of the oxygen that diffuses through the plastic bucket or airlock since we can make beer in plastic buckets and it doesn't go stale.
 

eastoak

Well-Known Member
Joined
Jan 4, 2011
Messages
3,306
Reaction score
174
Location
oakland
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.
i've seen them at morebeer.
 

sweetcell

Protruding Member
HBT Supporter
Joined
Jan 15, 2012
Messages
5,452
Reaction score
1,215
Location
North Bend, WA
I crunched some numbers (I'm a engineer and nerd...). Here are the rates of oxygen diffusion if you assume that there is no oxygen inside the carboy (roughly correct and shouldn't affect the numbers much):
Airlock with water = 0.038 mg/day
Airlock with vodka = 0.052 mg/day
Aluminum foil = 10.9 mg/day (I assumed you can get the aluminum foil pressed down good so that there was a 1 micron gap between the glass and foil. The rate will be linear with the gap thickness so you can just scale it up if you think there is a larger gap.)

(...)

The funny thing is if you use a plastic bucket (HDPE) then you have a diffusion rate of ~15.8 mg/day of oxygen through the walls of the bucket so it doesn't really matter what you put on the top.
all hail the nerds... the geek shall inherit the earth.

how did you arrive at those numbers? what calculations/formulas did you use?

i find it interesting that there is a higher diffusion rate for vodka vs. water - is that a function of specific gravity? (i.e. water is more dense than alcohol).

a 1 micron gap for foil seems very optimistic. are you assuming a 1 micron gap all along the full edge/opening of the bucket? wrinkles in the foil will almost certainly ensure that there are are larger gaps than this.

thanks for dorking out for us. it's appreciated :mug:
 
OP
D

DrHop

Well-Known Member
Joined
Apr 14, 2012
Messages
175
Reaction score
11
Location
Berkeley
I just used ficks law of diffusion. For the aluminum foil my problem was set up for between the foil and glass lip of the carboy. I thought this would be the slowest process in getting from outside to inside. I knew the concentration difference, I assumed a gap thickness between the foil and carboy and I knew the diameter and lip thickness of the carboy. I found the diffusion coefficient online.

For the airlock I assumed there was a 1 inch path length to get from outside to the inside of the carboy through water. I knew the annular cross-sectional area of the airlock. I looked up the solubility of oxygen in water and assumed the top surface of the airlock water was in equilibrium with the atmosphere which gave me my concentration gradient. I looked up the diffusion coefficient online. Alcohol increases the solubility and diffusion coefficient of oxygen a little.

The 1 micron gap is almost definitely optimistic but it's a nice round number.
 

bambrew

Active Member
Joined
Sep 4, 2009
Messages
38
Reaction score
0
Location
sacramento, ca
A breathable bung might not only sound hilarious but also be a nice solution to your problem. I enjoy them immensely.
 
Top