Stop Putting Airlocks on Your Starters!

Remember, starters are for growing yeast not growing beer; yeast need the exchange of oxygen to grow and slapping on an airlock is counterproductive to that aim. You don't really want just a simple ferment.

Aluminum foil = airlock (my nod to Pseudochef).

The Brewing Network.com - :

Foam stoppers sold at northernbrewer are also a good way to allow sanitary 2-way gas flow on an erlenmeyer flask or carboy. I guess you probably wouldn't want to shake a starter with one of those on, but I have a stirplate.

Foam stoppers sold at northernbrewer are also a good way to allow sanitary 2-way gas flow on an erlenmeyer flask or carboy.

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Absolutely, the key is gas exchange.

SCA homebrew myth #142...busted.

Some people use foil on primaries also.

Soperbrew said:

Some people use foil on primaries also.

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I've been known to do that.

Thanks, flyangler!

Soperbrew said:

Some people use foil on primaries also.

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Damn skippy we do



*Tangent: foil on primary is not just because I'm lazy, but because it allows less pressure forcing back on the yeast. This leads to a healthier fermentation and drives attenuation. Another BN link, but check out the last show from the White Bros. on The Session. If I have some time today, I'll figure out exactly when the topic comes up.

Also, here is a quote from an online chat with Chris White: "On CO2, reckon that a small amount of dissolved CO2 in a fermentation will seriously reduce yeast performance. Even the small partial pressure of CO2 built up under an airlock will have an effect."

and

"I don't like airlocks, I don't think they are needed in primary. I say keep them off and only put on when fermentation starts to slow down. Prior to that, some loose foil is all you need on top....I would not seal the lid, just put loose foil around the sides. You will notice a faster fermentaiton- less CO2 stress."

Source. (Chat Transcripts - Dr. Chris White returns - BrewBoard)

End tangent*

Pseudochef,

I've heard snippets here and there regarding the effects of CO2 pressure on yeast health; thanks for sharing that. I've not actually done any experiments regarding attenuation and pressure, but I'd be interested in those who have.

But they look so CUUUTE on growlers or Flasks...

Actually I have noticed that when I use foil they seem to take off quicker and I actually see real krausens on them.

I haven't really done any experiments, either...it really just evolved out of habit from work where we grow our cultures with foil. I heard him mention it once and then I started looking for more research and that was the jist of what I found. I haven't had any stuck fermentations or anything, so I don't "fix" whatever's broken.

I will have to do a side-by-side one of these days, I suppose.

AnOldUR said:

Would one of these in a stopper serve the same purpose, but relieve any stress about contamination?

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It would, but to ease your fear, I would suspect some RDWHAHB to be a good prescription as well. Unless you have some sort of fruit fly infestation or something, Foil is perfectly safe. No bacterium or wild yeast is going to fly up, underneath a piece of foil. Everything is falling down. If you are worried, try the foam stoppers mentioned earlier.

I've always used foil on starters, now I'm thinking about doing it with primaries as well.

I don't think it matters either way if you have a stir-plate. (I always use foil though).

Lets say you start out with a 2 L flask with 1L of wort in it. You put it on the stir-plate and it builds up to the 10ppm or so O2 that you can get from exposure to air. Then as it stirs it will emit Co2 but the air above it is being constantly stirred so what goes out from the airlock/aluminum foil is a mixture of air and Co2, and there is still air and O2 in the flask, so the wort continues to pick up O2.

ppm of oxygen in wort is maxed at 8-10ppm when using air and room temp wort (I've read) Air is 200,000 ppm oxygen. So even after 1L of Co2 has been produced (assuming a stir-plate) you'll have 100,000 ppm of O2 in the air in the flask still, which will keep dissolving in the wort as it gets used up, and so on.

I think this is one of the reasons that a stir-plate will give you 2-3 times as much yeast growth as a shaken starter. When you just put an airlock or aluminum foil on the flask it will still develop a layer of Co2 and evenly push out the oxygen as it ferments, since the Co2 is slightly heavier than air.

Just some thoughts I was having, the numbers I found online (sources later once I re-find them...), the process is just my theory.

This is the most important thread of 2009.

Yep, I just started doing it for fermentation as well.

AnOldUr: I don't think you need to worry about contamination, really. The bugs, etc., that are interested in infecting your wort can't fly, they just float and settle. So as long as it's relatively well protected, the chances of bacteria or wild yeast being able to navigate their way up around the foil are vanishingly small.

Tonedef131 said:

This is the most important thread of 2009.

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Seriously though, I can't think of a single reason NOT to forgo those pesky airlocks and just stick with aluminum foil (earlier concerns about fruitflies not withstanding).

What are the environmental concerns associated with just using foil?

Certainly you're not going to have vigorous mixing through the foil, though there will be some exchange. Proper pitching rates should give the yeast a serious leg up on any airborne bugs and the hops should help out as well, but...

You've gone through all the trouble to sanitize your gear and keep everything clean, and now you're not going to seal the easiest thing to seal? A lot of folks would say that's counterintuitive.

Moreover, we don't all have ideal brew spaces. I ferment in an unfinished basement. It's not nasty or anything, but a concrete floor and walls with the laundry and a woodworking bench nearby isn't nearly as sanitary a proper brewhouse should be. Moreover, most of us leave our starters on the kitchen counter or similar. There's a lot of nasty airborne stuff in the kitchen, just given vapors from cooking.


Sterile cotton plugs for the paranoid?

TrojanMan said:

What are the environmental concerns associated with just using foil?

Certainly you're not going to have vigorous mixing through the foil, though there will be some exchange. Proper pitching rates should give the yeast a serious leg up on any airborne bugs and the hops should help out as well, but...

You've gone through all the trouble to sanitize your gear and keep everything clean, and now you're not going to seal the easiest thing to seal? A lot of folks would say that's counterintuitive.

Moreover, we don't all have ideal brew spaces. I ferment in an unfinished basement. It's not nasty or anything, but a concrete floor and walls with the laundry and a woodworking bench nearby isn't nearly as sanitary a proper brewhouse should be. Moreover, most of us leave our starters on the kitchen counter or similar. There's a lot of nasty airborne stuff in the kitchen, just given vapors from cooking.


Sterile cotton plugs for the paranoid?

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See my post and PseudoChef's post. Bacteria and wild yeast cannot "fly", unless they're attached to a literal fly. Bacteria and wild yeast are heavier than air (obviously) and will fall down. So I'm not quite sure why you're worried about them falling up between the boil and the neck, then down again into the starter.

Oh, and when it comes to matters like this, I think it best to trust the folks at White Labs more than your own paranoia.

TrojanMan said:

What are the environmental concerns associated with just using foil?

Certainly you're not going to have vigorous mixing through the foil, though there will be some exchange. Proper pitching rates should give the yeast a serious leg up on any airborne bugs and the hops should help out as well, but...

You've gone through all the trouble to sanitize your gear and keep everything clean, and now you're not going to seal the easiest thing to seal? A lot of folks would say that's counterintuitive.

Moreover, we don't all have ideal brew spaces. I ferment in an unfinished basement. It's not nasty or anything, but a concrete floor and walls with the laundry and a woodworking bench nearby isn't nearly as sanitary a proper brewhouse should be. Moreover, most of us leave our starters on the kitchen counter or similar. There's a lot of nasty airborne stuff in the kitchen, just given vapors from cooking.


Sterile cotton plugs for the paranoid?

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You have two important factors working in your favor:

(1) Vigorous, healthy yeast. Brewer's yeast are voracious buggers and quite good at outcompeting wayward bacterium or other spoilage organisms. When you sanitize, you don't kill everything.

(2) Positive pressure. Once the ferment commences, there is significant production of CO2. This venting pushes out anything that maybe be falling through the air.

Open fermentation works:

flyangler18 said:

Seriously though, I can't think of a single reason NOT to forgo those pesky airlocks and just stick with aluminum foil (earlier concerns about fruitflies not withstanding).

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What about that comforting "bloop, bloop, bloop" that helps me sleep at night

AnOldUR said:

What about that comforting "bloop, bloop, bloop" that helps me sleep at night

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Here's an idea: record the sound, then play it in your bedside radio. You could even market it, like those "sounds of the ocean" CD's. "Sounds of the Brewery".

flyangler18 said:

Pseudochef,

I've heard snippets here and there regarding the effects of CO2 pressure on yeast health; thanks for sharing that. I've not actually done any experiments regarding attenuation and pressure, but I'd be interested in those who have.

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slightly
flyangler

I had a thought about this recently.

Has anyone tried to use an old propane tank to seal in a yeast and sugar water? Then watch the pressure regulator to see how high a yeast can go within a pressurized system. I figure at some point the yeast will not be able to over come the tank pressure to continue working.

Then increase the amount of sugar and yeast count to see if the final pressure increases.

Plus you could use the built up CO2 to carb a keg or something similar.

I'm sold. new process change going forward.

I know people who use saran wrap on their primaries as well...

I am thinking about using a cornie for a primary this weekend. Should I just pull off the gas in connector and put foil over the hole?

Brew-Happy said:

slightly
flyangler

I had a thought about this recently.

Has anyone tried to use an old propane tank to seal in a yeast and sugar water? Then watch the pressure regulator to see how high a yeast can go within a pressurized system. I figure at some point the yeast will not be able to over come the tank pressure to continue working.

Then increase the amount of sugar and yeast count to see if the final pressure increases.

Plus you could use the built up CO2 to carb a keg or something similar.

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huge thread about that
https://www.homebrewtalk.com/f13/closed-system-pressurized-fermentation-technique-44344/

Good job, flyangler. I was thinking about this a couple days ago when I dropped my airlock and it cracked. I just tossed the pail top on and covered the grommet with foil. Now I know I could have just covered the whole thing with foil.

But you know, with advice like this, threads like these https://www.homebrewtalk.com/f39/rubber-seal-fell-fermenter-104477/ will disappear.

shecky said:

I just tossed the pail top on and covered the grommet with foil. Now I know I could have just covered the whole thing with foil.

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Even better, get a sheet of plexiglass cut slightly larger than the footprint of the ale pail. Sanitize and set it on top. No need to snap those PITA lids into place, either.

flyangler18 said:

Even better, get a sheet of plexiglass cut slightly larger than the footprint of the ale pail. Sanitize and set it on top. No need to snap those PITA lids into place, either.

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That, too. I'm curious, though. What if you get a violent ferment? I suppose it doesn't matter, what with all that positive pressure making it impossible for anything to fall in. You would, however, have a big ol, mess. (speaking for those of us who do most of our primaries in buckets).

EDIT: Duh, could just put the bucket in a larger bin to catch everything. Coffee hasn't kicked in yet.

TrojanMan said:

What are the environmental concerns associated with just using foil?

Certainly you're not going to have vigorous mixing through the foil, though there will be some exchange. Proper pitching rates should give the yeast a serious leg up on any airborne bugs and the hops should help out as well, but...

You've gone through all the trouble to sanitize your gear and keep everything clean, and now you're not going to seal the easiest thing to seal? A lot of folks would say that's counterintuitive.

Moreover, we don't all have ideal brew spaces. I ferment in an unfinished basement. It's not nasty or anything, but a concrete floor and walls with the laundry and a woodworking bench nearby isn't nearly as sanitary a proper brewhouse should be. Moreover, most of us leave our starters on the kitchen counter or similar. There's a lot of nasty airborne stuff in the kitchen, just given vapors from cooking.


Sterile cotton plugs for the paranoid?

Click to expand...

Walk into most science labs that work with sterile media and cultures and just look at all the foil covering the tops of their flasks.

Duh, could just put the bucket in a larger bin to catch everything.

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Bingo. We have a winner.

Very informative. PROST!

This is an excellent thread. :rockin:


I was planning to put together a starter this evening and I have newfound inspiration. It's just for a low-gravity pale ale (gotta have something to session, right?) but I'm excited to see how this works out.

I am absolutely fired up now.

AnOldUR said:

Would one of these in a stopper serve the same purpose, but relieve any stress about contamination?

Click to expand...

I don't think there should be any concern about contamination. Bacteria and yeast travel through the air on dust particles. Unless you have strong drafts, foil is fine. If you are really concerned, the foam plugs are cheaper and can be autoclaved. My problem with these filters is, how do you keep the filter itself sanitary? I would get the foam plugs and boil them between uses or autoclave (pressure cook) if convenient.

I can't see too much air exchange going on once the CO2 blanket gets formed. I'm guessing that once that happens there is a whole lot of CO2 above the starter, and not much else.

But I do agree that there is no need for airlock and that foil would be easier and just as safe for contamination (unless you feel the need to pull that foil off every other hour for whatever reason...)

Homercidal said:

I can't see too much air exchange going on once the CO2 blanket gets formed. I'm guessing that once that happens there is a whole lot of CO2 above the starter, and not much else.

But I do agree that there is no need for airlock and that foil would be easier and just as safe for contamination (unless you feel the need to pull that foil off every other hour for whatever reason...)

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I may not be an expert on starters but I would tend to agree with Homercidal. CO2 is heavier than O2 it will stay in the flask. I don't think the stir plate will mix the O2 into the CO2 all that well. I think my next starter I will hit the starter every few hours with the O2 tank and stone see if there is a difference

springer said:

I may not be an expert on starters but I would tend to agree with Homercidal. CO2 is heavier than O2 it will stay in the flask. I don't think the stir plate will mix the O2 into the CO2 all that well. I think my next starter I will hit the starter every few hours with the O2 tank and stone see if there is a difference

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By keeping the yeast on the stirplate, you're delaying fermentation. When the yeast switch from an aerobic to anaerobic phase, then fermentation starts.

I know a stirplate mixes the air and Co2 very well, just put some water in, get a 1L vortex and blow some smoke in the flask.

I use big plastic soda bottles for starters. That way I can easily squeeze some CO2 out, release it and it breathes fresh air in to aid yest growth. I just leave the cap on loose.

AnOldUR said:

Would one of these in a stopper serve the same purpose, but relieve any stress about contamination?

Click to expand...

Those puppies (the ones I use in the lab anyway) are designed for a one way air flow. They are not going to get the exchange being talked about here (air in, CO2 out). Plus, if they get wet, they clog, then your system is pressurized.

As a working scientist who grows bacteria that need lots of air (oxygen), +1 on just using foil. It really is what we do. Foam bungs work well too. Continuous shaking/stirring (especially in a baffled flask) is required for good gas exchange.

Saran wrap is not so good, as it is not very permeable to gases (but you can get something like saran wrap that is designed to be permeable, for just this purpose).