The co2 "blanket"

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Hi everybody,
I have read several times about the co2 "blanket" that forms in our FVs and how it protects the beer from oxidation...

Is that really so?

CO2 should settle at the bottom but I guess it can easily disturbed by even the most suttle current, specially if fermentation isn't active, right?

If I crack open my fermentation bucket to drop in some hops or add a fining agent, wouldn't that be sufficient to get some air in which will diffuse with the CO2 and just oxidize the beer?

Thanks
pp
 
What I've read is that there's no such thing. Suspicion is that it comes from people using dry ice which, as it sublimates, has a very cold CO2 offgassing from it--so cold that it settles. That can create a CO2 blanket but that's not what's happening in our case.

If opening a bucket to drop in hops or add a fining agent was a huge oxidation problem, you'd read a lot about it.

I use the Big Mouth Bubbler which has a smaller opening than a bucket (which btw is the worst). I carefully remove the lid (opening is about 13 cm), pour in the finings, then gently reseal.

You'd be better off gently removing the stopper and pouring in the finings or hops (hopefully in pellet form) through the bung hole. As the hops or finings enter the fermentation bucket, they displace gas which exits through the bung hole. Then replace the stopper.
 
It's a bit of myth, have a look at Fick's law. You don't want to be opening your bucket much after fermentation is over. You can add hops and finings while it's still fermenting ( a couple of points above FG) and the yeast will scavenge any o2 much better than when it's dropped out - similar to how beer is cask conditioned for example

Or do what mongoose suggests :)
 
pp,

No - gases don't work that way. They don't settle. Once you open the fermenter, oxygen (and other gases) will start to diffuse into the CO2 in the fermenter. You don't immediately lose ALL your CO2, but you do quickly introduce other gases. If the CO2 blanket was real, all the people living in valleys would suffocate on calm days. Check this out - diffusion of bromine (really dense) in air.

[ame]https://m.youtube.com/watch?v=_oLPBnhOCjM[/ame]

Pliny

ETA - wow. I'm a slow typer. You've got your answer - twice - before I got done typing.
 
Exactly. The Ideal Gas Law and other laws of physics come into play.

Keep in mind that during primary, when tons of co2 is being produced, that there is indeed a protective effect over the beer (or wine).

I went to a distillery one time where during the tour we were standing on a balcony over an open fermenter. The guide encouraged everyone to lean over and take a deep breath to "smell" the great aroma of corn mash. Many people gasped and coughed due to the high c02 level coming off.

I was a winemaker long before I brewed a single batch of beer, and we often do open primaries for the first 5-7 days, even stirring the batch to get rid of excess c02 (which is poisonous to yeast).

But after that, when c02 production slows, that 'blanket' is gone and gasses will mix readily. Just like in our environment, our air is full of nitrogen and oxygen, mixed up and not separated.
 
Think you for all your replies! Got to find a better method to put hops in the bucket i guess.
 
If opening a bucket to drop in hops or add a fining agent was a huge oxidation problem, you'd read a lot about it.

It actually is. Many people are trying to find a way to avoid it

http://www.bear-flavored.com/2014/09/how-i-dry-hop-my-ipas-with-no-oxygen.html

As far as doing so without such a system, you could dry hop while primary is still going and then bottle without adding more hops. Yeast are your friend as primary is winding down. And the O2 introduced during bottling can be mitigated by naturally carbonated
 
It actually is. Many people are trying to find a way to avoid it

http://www.bear-flavored.com/2014/09/how-i-dry-hop-my-ipas-with-no-oxygen.html

As far as doing so without such a system, you could dry hop while primary is still going and then bottle without adding more hops. Yeast are your friend as primary is winding down. And the O2 introduced during bottling can be mitigated by naturally carbonated

Well, we're going to have to disagree here. I'm not saying it's not worth trying to avoid it--of course it is. It's just that lots of dry hopping is going on, and people routinely use buckets to ferment, and they have to remove a lid to rack to bottle or keg, or to dry hop, and if this was truly a huge problem, it would not be done.
 
What about getting some small (but strong) magnets, sanitize them and put one in a hop bag w/ the hops, and use the other magnet on the outside of the lid. Keeps the hops suspended above the fermenting beer until you're ready to dry hop. Then remove the outter magnet and let them drop into the beer? Obviously this would only work if you had strong a enough magnet, enough head space in your bucket for the amount of hops. No idea if this would actually work or if a magnet would jack up your beer but just something off the cuff I thought of. Probably too problematic to work but who knows.
 
pp,

No - gases don't work that way. They don't settle. Once you open the fermenter, oxygen (and other gases) will start to diffuse into the CO2 in the fermenter. You don't immediately lose ALL your CO2, but you do quickly introduce other gases. If the CO2 blanket was real, all the people living in valleys would suffocate on calm days. Check this out - diffusion of bromine (really dense) in air.

https://m.youtube.com/watch?v=_oLPBnhOCjM

Pliny

ETA - wow. I'm a slow typer. You've got your answer - twice - before I got done typing.


The people living in the valley are also surrounded by vegetation which converts the CO2 to O2!
 
Well, we're going to have to disagree here. I'm not saying it's not worth trying to avoid it--of course it is. It's just that lots of dry hopping is going on, and people routinely use buckets to ferment, and they have to remove a lid to rack to bottle or keg, or to dry hop, and if this was truly a huge problem, it would not be done.

Oxidation IS a huge problem. In judging competitions, the biggest and most common flaw I see is varying degrees of oxidation. One reason dryhopping fades so fast is due to oxidation.

Luckily, with IPAs and other dryhopped beers, we tend to drink them pretty fast before there are the bigger signs of oxidation like a sweeter taste (madeira-like flavors) or a darkening of the color.

That said, I often dryhop my beers in primary, and then keg them 5 days later. I do what I can to avoid excess contact with room air, but sometimes it's not practical.
 
There doesn't seem to be a really solid answer to this question. Yes, gasses mix, but remember that a fermenter (esp a carboy) is a closed space with positive outward pressure. So it seems like it is reasonably covered by CO2 just because it pushes the O2 out during fermentation.

When you take the lid off a bucket, you really are exposing it to a lot of O2, so you should minimize it (crack it, drop in, close it). Less so with a big mouth, less with a carboy. Your hops also create nucleation sites for the CO2 in the beer, which bubbles out, creating positive pressure again.

But we all bottle, right, and the headspace of the bottle is filled with air (O2, nitrogen, CO2, radon from the basement, etc.), and then capped. The yeast product CO2, but the air is not displaced - it's in the bottle. So there might not be a blanket, but obviously air in the headspace must not be crucial. And the ratio is about the same in a 5 gallon fermenter and a 12 oz bottle. (Not to mention that even the most careful racking exposes the beer to air when bottling.)

This seems like a tiny concern compared to other aspects of brewing.
 
Oxidation IS a huge problem. In judging competitions, the biggest and most common flaw I see is varying degrees of oxidation. One reason dryhopping fades so fast is due to oxidation.

Luckily, with IPAs and other dryhopped beers, we tend to drink them pretty fast before there are the bigger signs of oxidation like a sweeter taste (madeira-like flavors) or a darkening of the color.

That said, I often dryhop my beers in primary, and then keg them 5 days later. I do what I can to avoid excess contact with room air, but sometimes it's not practical.

This seems like the best way to avoid it - do it all in primary, even when dryhopping.
 
I use Ale Pails for fermentation and gave up on dry hopping in them years ago because I was tired of fussing with hops and fermenters. What I have been doing instead is adding aroma hops to the kettle during the boil and adding whirlpool hops to the kettle at flameout. Every once in while I'll add hops to a corny keg while it's connected to a Co2 line. Needless to say, oxidation is not an issue for me doing it this way.

What about purging the headspace of the fermentor with Co2, after adding the dry hops and snapping the lid back on? Wouldn't that be the same idea as purging a corny keg with Co2, to remove as much O2 as possible, before filling the keg with beer?
 
Oxidation IS a huge problem. In judging competitions, the biggest and most common flaw I see is varying degrees of oxidation. One reason dryhopping fades so fast is due to oxidation.

Luckily, with IPAs and other dryhopped beers, we tend to drink them pretty fast before there are the bigger signs of oxidation like a sweeter taste (madeira-like flavors) or a darkening of the color.

That said, I often dryhop my beers in primary, and then keg them 5 days later. I do what I can to avoid excess contact with room air, but sometimes it's not practical.

I'm hardly going to lecture you on this stuff, Yooper--me and my total of 14 or 15 batches made. :)

However--and you knew there had to be a however :)--I fear what I'm saying is being lost here. I know that oxidation is a problem, and oxidation is a big reason for hoppy aroma and flavor to dissipate. But it doesn't appear to me--maybe I'm not reading the right stuff--that people in general are making huge efforts to avoid oxidation in order to get drinkable and in some cases excellent beer.

If I were doing this--and I may at some point, but I am not a huge IPA fan so I tend toward maltier brews--I'd add dry hops through my bunghole on the top of my BMB, and might even use a 2-hole lid through which I would vent low-pressure CO2 into the fermenter through a stopper in one hole while I added the pellet hops through the other hole in the lid. That would create positive CO2 pressure preventing almost all of the external air from mixing while I added the hops.

But I don't see people using contraptions like this--again, maybe I'm not reading the right stuff. That tells me something--they must be able to produce reasonably tasty brews without all the elaborate machinations like I describe above.

Perhaps they drink their hoppy brews fast before oxidation sets in--but then that's a process adjustment of sorts.

Now, having said all that, I do what I can to avoid oxidation. I even add low pressure CO2 in the top of my fermenter as I rack it into the keg, which has been purged of Star-San using CO2 to remove almost all the O2. So it's not that I don't believe oxidation isn't a problem, just that if it were a huge problem, we'd see much more complicated efforts to avoid it than we do.

BTW, here's how I get the CO2 into the top of my fermenter just so you don't think I don't really do this :). I even have a further adjustment--I now use a screwdriver to hold open the relief valve in the lid rather than open the lid and thus the CO2 inside to outside air.

o2freeracking.jpg
 
I'm hardly going to lecture you on this stuff, Yooper--me and my total of 14 or 15 batches made. :)

However--and you knew there had to be a however :)--I fear what I'm saying is being lost here. I know that oxidation is a problem, and oxidation is a big reason for hoppy aroma and flavor to dissipate. But it doesn't appear to me--maybe I'm not reading the right stuff--that people in general are making huge efforts to avoid oxidation in order to get drinkable and in some cases excellent beer.

If I were doing this--and I may at some point, but I am not a huge IPA fan so I tend toward maltier brews--I'd add dry hops through my bunghole on the top of my BMB, and might even use a 2-hole lid through which I would vent low-pressure CO2 into the fermenter through a stopper in one hole while I added the pellet hops through the other hole in the lid. That would create positive CO2 pressure preventing almost all of the external air from mixing while I added the hops.

But I don't see people using contraptions like this--again, maybe I'm not reading the right stuff. That tells me something--they must be able to produce reasonably tasty brews without all the elaborate machinations like I describe above.

Perhaps they drink their hoppy brews fast before oxidation sets in--but then that's a process adjustment of sorts.

Now, having said all that, I do what I can to avoid oxidation. I even add low pressure CO2 in the top of my fermenter as I rack it into the keg, which has been purged of Star-San using CO2 to remove almost all the O2. So it's not that I don't believe oxidation isn't a problem, just that if it were a huge problem, we'd see much more complicated efforts to avoid it than we do.

BTW, here's how I get the CO2 into the top of my fermenter just so you don't think I don't really do this :). I even have a further adjustment--I now use a screwdriver to hold open the relief valve in the lid rather than open the lid and thus the CO2 inside to outside air.

Cool System. Not to sharp shoot here but couldn't you just pull the ring on your PRV, turn it 90% and let it hold itself open? That way you don't need a screwdriver.
 
I'm hardly going to lecture you on this stuff, Yooper--me and my total of 14 or 15 batches made. :)

However--and you knew there had to be a however :)--I fear what I'm saying is being lost here. I know that oxidation is a problem, and oxidation is a big reason for hoppy aroma and flavor to dissipate. But it doesn't appear to me--maybe I'm not reading the right stuff--that people in general are making huge efforts to avoid oxidation in order to get drinkable and in some cases excellent beer.

I think that people in general do NOT make excellent beer. Oh, there are some, and quite a few, that make very good beer and a few excellent ones are out there.

But I think sooooooo many other homebrewers have "ugly baby syndrome". You know, when they have this hideously ugly offspring and go on and on about how adorable/cute/beautiful this child is, because it's theirs and they have their love blinders on. That's so true of homebrewers as well. I've had people send me their fabulously fantastic beers, so proudly, and the beers were often mediocre or even worse.

One guy sent me his best lager and he was so proud. The beer was apparently brewed with alkaline water, and was astringent and harsh and I couldn't hardly get it down. I did nicely mention he may want to look at water chemistry and get the mash pH down, and he did say that he noticed "something" that wasn't in commercial beers.

Still, they had UBS and LOVED those beers. And that's ok- if the brewer is making beer he/she loves and is enjoying the process, that is what I define as "great beer".

Oxidation changes the beer, and sometimes it's a small barely perceptible change, and it always gets worse with time. That is part of the flavor profile of some beers that are aged a long time- think barleywine with those sherry and toffee notes- but is generally a flaw in other beers. So, one of those UBS beers may not win awards, and often the brewer is pissed off when they enter a competition and score a 21 or something. That happens all the time.

Again, if someone is making beer they love and see no need for improvement, I am their biggest cheerleader. I think that's great, and I think they should absolutely continue what they are doing. So I'm not trying to be a naysayer here, I'm just saying that often flavor is in the tastebuds of the beerholder.
 
This seems like the best way to avoid it - do it all in primary, even when dryhopping.

I often do that. This brew, I'm harvesting my yeast (Vermont ale yeast in Heady Topper clone), so I'm debating on what to do with the 5 ounces of dryhops in each 5 gallons. At this point, I'm thinking that I'll rack to the purged keg, over the bagged dryhops, wait 5 days and then transfer via c02 to the serving kegs.
 
I often do that. This brew, I'm harvesting my yeast (Vermont ale yeast in Heady Topper clone), so I'm debating on what to do with the 5 ounces of dryhops in each 5 gallons. At this point, I'm thinking that I'll rack to the purged keg, over the bagged dryhops, wait 5 days and then transfer via c02 to the serving kegs.

Why not add the bagged dry hops to the primary (sink them with marbles if necessary), and let it run 5 days. Then transfer to the serving keg?
 
When my son was born, I said, that thing looks like a sea monkey which made my wife quite upset.
 
Why not add the bagged dry hops to the primary (sink them with marbles if necessary), and let it run 5 days. Then transfer to the serving keg?

Because I am saving this yeast, and adding 5 ounces of dryhops to it, even in a bag, could really cause some difficulties for me.

There are 30 ounces of hops in this batch, so I've been more aware of trying to keep the trub to a minimum by straining the wort a little, leaving more in the boil kettle, etc, and I don't want to deal with pellet debris in the yeast that I"m saving. Those pellets disintegrate pretty well, and I have a mix of pellets and whole hops to use.
 
Oh, one other thing I forgot to mention that I think is important is that long primaries with large headspace could be troublesome as well, for those who are doing those 4 week (or longer) primaries thinking that it preserves this mythical c02 blanket. There was an eyeopening study done on closures and better bottles that really has surprising results:
http://www.better-bottle.com/pdf/CarboyPermeabilityStudy.pdf (carboy stuff)
http://www.mocon.com/assets/documents/PPS_Article_highq.pdf
This was done to test the oxygen permeability of the better bottles, but the best part of what I learned was in the closures part.

I started looking around at this when I had a wine that got a little bit of oxidation in a glass carboy, with one of those orange "carboy caps".

Also, keep in mind that even under airlock, oxygen still enters the fermenter through cracks in the airlock, and even through the water or vodka in the airlock. That's one reason winemakers are so meticulous about always topping up their wine, as the wine spends much more time in the carboy than a typical beer. There is maybe an inch or so of headspace in the narrowest part of my carboys, so that there is perhaps an inch of wine exposed to the area just below the bung. This has a protective effect on the wine, but many winemakers use sulfites routinely in the amount of 50 ppm as an antioxidant. With beer, that is rarely done.
 
Oh, one other thing I forgot to mention that I think is important is that long primaries with large headspace could be troublesome as well, for those who are doing those 4 week (or longer) primaries thinking that it preserves this mythical c02 blanket. There was an eyeopening study done on closures and better bottles that really has surprising results:
http://www.better-bottle.com/pdf/CarboyPermeabilityStudy.pdf (carboy stuff)
http://www.mocon.com/assets/documents/PPS_Article_highq.pdf
This was done to test the oxygen permeability of the better bottles, but the best part of what I learned was in the closures part.

I started looking around at this when I had a wine that got a little bit of oxidation in a glass carboy, with one of those orange "carboy caps".

Also, keep in mind that even under airlock, oxygen still enters the fermenter through cracks in the airlock, and even through the water or vodka in the airlock. That's one reason winemakers are so meticulous about always topping up their wine, as the wine spends much more time in the carboy than a typical beer. There is maybe an inch or so of headspace in the narrowest part of my carboys, so that there is perhaps an inch of wine exposed to the area just below the bung. This has a protective effect on the wine, but many winemakers use sulfites routinely in the amount of 50 ppm as an antioxidant. With beer, that is rarely done.

Why aren't sulphites used as preservatives/antioxidant in beer making ?
Aside used for removing chlorine, you don't read about other uses for it.
 
Oh, one other thing I forgot to mention that I think is important is that long primaries with large headspace could be troublesome as well, for those who are doing those 4 week (or longer) primaries thinking that it preserves this mythical c02 blanket. There was an eyeopening study done on closures and better bottles that really has surprising results:
http://www.better-bottle.com/pdf/CarboyPermeabilityStudy.pdf (carboy stuff)
http://www.mocon.com/assets/documents/PPS_Article_highq.pdf
This was done to test the oxygen permeability of the better bottles, but the best part of what I learned was in the closures part.

I started looking around at this when I had a wine that got a little bit of oxidation in a glass carboy, with one of those orange "carboy caps".

Also, keep in mind that even under airlock, oxygen still enters the fermenter through cracks in the airlock, and even through the water or vodka in the airlock. That's one reason winemakers are so meticulous about always topping up their wine, as the wine spends much more time in the carboy than a typical beer. There is maybe an inch or so of headspace in the narrowest part of my carboys, so that there is perhaps an inch of wine exposed to the area just below the bung. This has a protective effect on the wine, but many winemakers use sulfites routinely in the amount of 50 ppm as an antioxidant. With beer, that is rarely done.
Thanks for the links Yoop. Very informative studies.

Brew on :mug:
 
Yooper has been a cheerleader for a beer or two of mine. :)

Oh, well, you being a Ninkasi winner and all, I did manage to choke a few down..........................:p

Seriously the most surprising beer of yours that I thought was outstanding was the habanero IPA. I never had a pepper beer that I enjoyed all that much, and you manage to do that extraordinarily well.

The thing that is surprising to new brewers is that you can make fantastic beer in a bucket and a pot, and you don't really need all that fancy beer. I've had some wonderful beers made with rustic equipment, and awful beers out of sabco brewmagics. It's really all about the technique and skill and attention by the brewer.

Minimizing oxygen exposure is important, but only one of the keys to great beer. Other things, like yeast pitching rate, temperature control, etc, are equally important. If one is ignored, the beer will suffer.
 
There was an eyeopening study done on closures and better bottles that really has surprising results:
http://www.better-bottle.com/pdf/CarboyPermeabilityStudy.pdf (carboy stuff)
http://www.mocon.com/assets/documents/PPS_Article_highq.pdf
This was done to test the oxygen permeability of the better bottles, but the best part of what I learned was in the closures part.

Wow, this has me wondering about the permeability of the silicon gasket on my SsBT Chronical fermenter. Fortunately any effect for me would be tempered by primary durations of three weeks or less. I do my aging in kegs.

Alt
 
I agree with Yooper that the #1 flaw I see in homebrew competitions that keep good beers from being great is oxidation. I bet if you polled some of the award-winning homebrewers in your area and asked them how they handle oxidation, few would answer 'I don't worry about it'. There is no co2 blanket, and every step in your process matters. It is up to each brewer to decide how much oxygen is acceptable in their wort/beer vs. the amount of time/effort needed to avoid it.

If you are bottle conditioning your beer, yeast is a great anti-oxidant and will absorb the headspace oxygen to keep any further oxidation from happening. It will not absorb oxidation already done to your beer from HSA/cold crashing/dry hopping/etc.
 
I agree with Yooper that the #1 flaw I see in homebrew competitions that keep good beers from being great is oxidation. I bet if you polled some of the award-winning homebrewers in your area and asked them how they handle oxidation, few would answer 'I don't worry about it'. There is no co2 blanket, and every step in your process matters. It is up to each brewer to decide how much oxygen is acceptable in their wort/beer vs. the amount of time/effort needed to avoid it.

If you are bottle conditioning your beer, yeast is a great anti-oxidant and will absorb the headspace oxygen to keep any further oxidation from happening. It will not absorb oxidation already done to your beer from HSA/cold crashing/dry hopping/etc.

Thanks for the comment.
I am at peace (for now) with the process up to the point where the beer reaches FG. From there I think I am picking up more oxygen than I should, considering beer happens in a bucket.

Based on a PDF posted in this thread, I was thinking of adding some sodium metabisulphite to scavenge some of the oxygen picked up to the point where the beer gets bottled. Would that be any good? I reckon my water has about 20ppm of sodium and was thinking of adding about 10ppm smb which would scavenge roughly 1.5ppm oxygen without significantly increasing the amount of sodium.

Don't know, the idea is probably nonsense... Just another stepping stone in the road of beer education.
 
Thanks for the comment.
I am at peace (for now) with the process up to the point where the beer reaches FG. From there I think I am picking up more oxygen than I should, considering beer happens in a bucket.

Based on a PDF posted in this thread, I was thinking of adding some sodium metabisulphite to scavenge some of the oxygen picked up to the point where the beer gets bottled. Would that be any good? I reckon my water has about 20ppm of sodium and was thinking of adding about 10ppm smb which would scavenge roughly 1.5ppm oxygen without significantly increasing the amount of sodium.

Don't know, the idea is probably nonsense... Just another stepping stone in the road of beer education.

It's not nonsense, although I don't know how rapidly the bucket would absorb CO2. You may want to check on the German brewing forums if you're interested in reducing DO
 
...if someone is making beer they love and see no need for improvement, I am their biggest cheerleader. I think that's great, and I think they should absolutely continue what they are doing. So I'm not trying to be a naysayer here, I'm just saying that often flavor is in the tastebuds of the beerholder.


+1. Ditto. IMO, this is the whole point of the hobby. Cheers!
 
Oh, one other thing I forgot to mention that I think is important is that long primaries with large headspace could be troublesome as well, for those who are doing those 4 week (or longer) primaries thinking that it preserves this mythical c02 blanket. There was an eyeopening study done on closures and better bottles that really has surprising results:
http://www.better-bottle.com/pdf/CarboyPermeabilityStudy.pdf (carboy stuff)
http://www.mocon.com/assets/documents/PPS_Article_highq.pdf
This was done to test the oxygen permeability of the better bottles, but the best part of what I learned was in the closures part.

I started looking around at this when I had a wine that got a little bit of oxidation in a glass carboy, with one of those orange "carboy caps".

Also, keep in mind that even under airlock, oxygen still enters the fermenter through cracks in the airlock, and even through the water or vodka in the airlock. That's one reason winemakers are so meticulous about always topping up their wine, as the wine spends much more time in the carboy than a typical beer. There is maybe an inch or so of headspace in the narrowest part of my carboys, so that there is perhaps an inch of wine exposed to the area just below the bung. This has a protective effect on the wine, but many winemakers use sulfites routinely in the amount of 50 ppm as an antioxidant. With beer, that is rarely done.



I have to admit I'm a bit surprised at the two articles. So, what are the best options we have to implement in our homebrewing, to combat the permeability issues with airlocks?


Thanks,
Dan
 
Let me say what I know about a CO2 blanket. If you are fermenting and the top to your fermenter is not air tight (we're talking a rather large fermente better than 20 gal) it'll hold til you run your batch provided you appreciate what your doing.
 
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