CO2 blanket poll

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Is the CO2 blanket real or a myth

  • There’s no such thing ... gases mix

    Votes: 42 93.3%
  • It’s real ... CO2 is heavier than air and will settle forming a blanket

    Votes: 3 6.7%

  • Total voters
    45
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Jtvann

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I keep seeing reputable people referring to a CO2 blanket. It seems to always lead to strong opinions.

I’m about to get into low oxygen dry hopping and saw the CO2 blanket brought up again.

What are your beliefs and why as far as home brewing.
 

IslandLizard

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There’s no such thing as a gas blanket ... gases mix!

However, In a narrow, deep vessel filled with a cover gas, when streaming in a cover gas through a side port, it will slow down the mixing below. Vessel shape matters!
Back in the early 70s in the chemistry labs, we stored oxygen sensitive compounds under Argon in special tubes with such side port. And then in the deep freeze at -80C. That seemed to work well enough. Not sure what they do now.
 
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Jtvann

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I’m in the boat of mix and the blanket is a myth but ...

When I’m done kegging I can remove my unitank lid and see the haze of gas left inside. That gas must be mostly CO2 from how a transfer. I’m wondering how much pressure plays into the equation. Obviously you can’t see a pure gas. Is there something to the pressure causing just enough of a phase change so that the CO2 has just enough of a liquid phase so that it can be seen.

I know I could look up a temperate and pressure chart for that info, but I’m lazy and don’t care enough.

If though that’s not complete BS, and there is a microscopic amount of denser CO2, I could see if sinking to form a layer.

I’m firmly in the gases mix group, but just looking to explain what I can physically see and maybe learn something in the process.
 

bracconiere

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i'm really not sure...but being that if you drop a few drop of food coloring in water, it will eventually mix in...i'm guessing gases mix....
 

Dgallo

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@VikeMan do you have that video link that shows the mixing of gases
 

Vale71

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I’m in the boat of mix and the blanket is a myth but ...

When I’m done kegging I can remove my unitank lid and see the haze of gas left inside. That gas must be mostly CO2 from how a transfer. I’m wondering how much pressure plays into the equation. Obviously you can’t see a pure gas. Is there something to the pressure causing just enough of a phase change so that the CO2 has just enough of a liquid phase so that it can be seen.

I know I could look up a temperate and pressure chart for that info, but I’m lazy and don’t care enough.

If though that’s not complete BS, and there is a microscopic amount of denser CO2, I could see if sinking to form a layer.

I’m firmly in the gases mix group, but just looking to explain what I can physically see and maybe learn something in the process.
I don't have to look it up and can tell you that liquid CO2 cannot exist at atmospheric pressure. That's the reason why dry ice can only sublimate and not liquefy, unlike water ice. What you're seing is condensation from water vapor. That's liquid water in the form of microscopic droplets and being liquid they do sink to the bottom, just very slowly because of the extremely high aerodinamic drag.
 
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Jtvann

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I don't have to look it up and can tell you that liquid CO2 cannot exist at atmospheric pressure. That's the reason why dry ice can only sublimate and not liquefy, unlike water ice. What you're seing is condensation from water vapor. That's liquid water in the form of microscopic droplets and being liquid they do sink to the bottom, just very slowly because of the extremely high aerodinamic drag.
Agreed, but when in a unitank under pressure, it’s not atmospheric pressure. When uncapping, it’s equalizes to atmospheric pressure as soon as it’s uncapped. That could explain what I see, but does a layer possibly exist under pressure?
 
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Jtvann

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Whatever. I don’t care about semantics of a single word on a topic that has nothing to do with religion.

Scratch the word “belief” for “think”
 

Vale71

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Agreed, but when in a unitank under pressure, it’s not atmospheric pressure. When uncapping, it’s equalizes to atmospheric pressure as soon as it’s uncapped. That could explain what I see, but does a layer possibly exist under pressure?
The triple point of CO2 is -56.6°C and 5.11 atm. This means that liquid CO2 cannot possibly exist in the range of temperature and pressure that you can have in your fermenter without having it blow up in your face.


Scroll to the end for the part about CO2.
And the answer to the layer existing under pressure is definitely not.
 

Vale71

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Whatever. I don’t care about semantics of a single word on a topic that has nothing to do with religion.

Scratch the word “belief” for “think”
Same difference but let's agree to just talk about CO2.
 

BrewnWKopperKat

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I’m about to get into low oxygen dry hopping
Some questions for you to consider (and follow-up on as appropriate):
  • Do you have a way to measure or otherwise evaluate changes in your process?
  • Are you able to measure oxygen ingress in your process?
  • Are you able to identify by taste the off flavors that oxidation causes?
 
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Jtvann

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Triple point is solid/liquid/gas all together. I don’t think anybody believes we have dry ice in our fermenters. The liquid gas line though has a much broader range. Still at low temps, looks like the pressure would need to be in the 30-40 psi range to phase shift.
 
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Jtvann

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Some questions for you to consider (and follow-up on as appropriate):
  • Do you have a way to measure or otherwise evaluate changes in your process?
  • Are you able to measure oxygen ingress in your process?
  • Are you able to identify by taste the off flavors that oxidation causes?

Nope
Nope
Nope/Maybe

Probably just doing it because it’ looks cool and I like tinkering with my system. Not sure it will help at all. Not sure I’ll know if it will help at all. For sure won’t ever measure outside of taste. Also sure it won’t hurt anything other than being wasteful of money.
 
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Jtvann

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don't they sell O2 sensors for cars? could hook one up to a rasberrypi, and install it in your fermenter! ;)
Raspberrypi sounds like something I’d avoid at Thanksgiving. That’s the extent of what I care to know about that.
 

eric19312

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Haha I'm only one who voted it's real. I will defend my vote. I agree it is not a barrier. But blanket is probably a decent characterization. Blankets are also not impervious to gas. They can slow it down but it's not going to stay under there forever.

My scientific evidence this is true is the pretty high quality of homebrew I've encountered from people (me included) fermenting in poorly sealed and airlocked plastic buckets. When I started I was brewing in plastic buckets and carboys and letting it go for 3 weeks before bottling. Is it likely that my beer picked up some oxygen. For sure it did, you got that video up there that proves it. Was it nasty oxidized crap? To me and those I shared it with and competitions I entered in into the answer was no.

I'm now fully into low oxygen dry hopping and all things low oxygen on the cold side and I wouldn't bother if I didn't think these were helping improve the quality of my beer by further reducing oxygen pick up. But that doesn't mean there is no such thing as a CO2 blanket.
 

bracconiere

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Vale71

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One last contribution and then I'm out. The reason you see that mist or fog forming is that:

1 - the atmosphere inside the fermenter is water vapor saturated for the current temperature
2 - as you release pressure gas expansion will cause the gas temperature inside the fermenter to drop and this causes the atmosphere to become over-saturated and some of the water will condense into droplets. This is exactly how convective clouds form in the sky by the way.

Okay, that was two reasons...
 

Jim R

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The bottom line is that no one should open his fermenter or keg and not expect some oxidation.
 

Birrofilo

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The question for the practical homebrewer IMHO is: will capping the neck of a filled bottle with CO2 expel most of the air in the neck and replace it with a mixture which is significantly richer in CO2 and poorer in O2 than before the purging? Can we reduce oxidization by purging the neck of the bottle with CO2?

This "do gas mix" question normally end up in a fair of equations and theoretical modelling about how gas behaves in a cave, on top of a mountain, or on Jupiter.

But what we really want is better beer, not better understanding of gas theory. The proof is in the glass. The "blanket" question is even secondary in respect to the "can we purge the neck by blowing in CO2 question", which is in turn secondary to the question "is the beer from a purged bottle better or worse or different than a non-purged" bottle.

I voted for n. 2 even though I am not interesting in the "do the CO2 settle" as much as "can I effectively purge the neck of the bottle". I'm with eric19312.
 

VikeMan

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The "blanket" question is even secondary in respect to the "can we purge the neck by blowing in CO2 question", which is in turn secondary to the question "is the beer from a purged bottle better or worse or different than a non-purged" bottle.
So, did you vote "it's real," and if so, did you vote that way based on your question, and not the one posed in the poll? I ask this because when people (including the OP, I'll wager) talk about CO2 blankets, they are almost invariably talking about CO2 in fermenters, produced by fermentation. They're not normally talking about purging or flooding receiving vessel's headspaces with CO2 before/during/after transfers, which is really quite a different thing.
 

Birrofilo

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@VikeMan

I think it's real that there is a blanket effect, because this is used by people working on solving real problems in real products (be it photography or food preparation) rather than speculating about theory on a homebrewing forum.

But the blanket effect is something that is somehow secondary. If you can expel the air in the fermenter by purging it with CO2 or another gas from a cylinder, then you go back to the initial problem. Homebrewers are interested in better beer not better gas theory understanding.

In a fermenter closed by a gorgogliatore* yes, the CO2 coming from the beer will "expel" the air, not the way a liquid would do, but certainly will decrease the inner content of O2 because external air does not enter and internal air will be more and more CO2. CO2 hasn't got a preferential pathway toward the exit leaving the previous air inside.

As an example, I have this quotation in my notes:
" As a chemist who works with oxygen reactive and mositure sensitive reagents, learning barrier and air free technique to exclude oxygen is something very basic to most all organic synthetic chemistry. And the food process industry has ALWAYS worked hard to minimize exposure to oxygen during all food process steps excluding baking and tunnel drying. I have always used dry nitrogen gas as a purge and blanket when cider and meadmaking. "

This can be found as a note to this text: Low Oxygen Brewing; Exploring LODO

You see, this person works with those problems, and he believes there is a blanket effect, and he says "purge and blanket" because he is not interested in the "blanket" question as separate from the "purge" question.

By the same token, in chemical photography people "purge and blanket" chemical solutions which are spoiled by oxygen. That stuff costs, and people do things with a reason.

I answered to "my question" rather than the question asked because I think that the real interest in an homebrewing forum is better beer.

* a bubbler?
 
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Jtvann

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So, did you vote "it's real," and if so, did you vote that way based on your question, and not the one posed in the poll? I ask this because when people (including the OP, I'll wager) talk about CO2 blankets, they are almost invariably talking about CO2 in fermenters, produced by fermentation. They're not normally talking about purging or flooding receiving vessel's headspaces with CO2 before/during/after transfers, which is really quite a different thing.
Yeah I was mainly talking about fermenters. Though my dry hopper is more of a purge situation. I read someone’s suggestion to purge and let settle a few minutes before purging again. The poll really isn’t about purging, but more the fermenter. I don’t mind discussion either way though.
 

BrewnWKopperKat

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Probably just doing it because it’ looks cool and I like tinkering with my system. Not sure it will help at all. Not sure I’ll know if it will help at all. For sure won’t ever measure outside of taste. Also sure it won’t hurt anything other than being wasteful of money.
If one likes to tinker, occasionally one has to spend ('waste') some money. :yes:
 

Birrofilo

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As a side note on the "fermenter blanket", I think this is of some interest:


If what is written here is exact, the usual 20 litres of wort produce between 400 and 600 litres of CO2. These CO2 comes from below and pushes away from the fermenter the 7 or 10 litres of air which are sitting on top of the wort.

Now, will this happen as if it is a liquid tide which pushes away the pre-existing air? Probably not. And I don't care either!
If 500 litres come from below and mix with the 10 litres existing, and no external air enters through the bubbler, I presume that the inside of the fermenter is basically free of oxygen. I don't care whether this should be termed a blanket or just a neck full of CO2, but it allows us to understand that bubblers are good and not putting the bubbler is probably not.

If you don't put the bubbler and put the cap on, the hole is so small that probably nothing will change, partially maybe because of the "blanket" effect. Some people say that they don't put the bubbler and they have no problem. I don't even think about doing it because I have flies in my house and because it's not so hard to put a bubbler, this is not a corner that I want to cut.

My interest in the blanket effect is nihil because I do use a bubbler and I am confident the fermenter will be full of CO2 on the neck.
 
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VikeMan

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@VikeMan
I answered to "my question" rather than the question asked because I think that the real interest in an homebrewing forum is better beer.
Since you're not interested in talking about gas theory, I'll just state this as my position.... CO2 "blankets" are not effective at doing anything other than very temporarily slowing down (through random collisions) any O2 that has entered the headspace. If "X" amount of O2 is in the headspace, "fX" amount of O2 will ultimately dissolve into the beer, regardless of other gasses present. The way to keep O2 out of beer is to keep fermenters closed and do closed transfers into thoroughly purged containers, via thoroughly purged tubing.

As a side note on the "fermenter blanket", I think this is of some interest:

Now, will this happen as if it is a liquid tide which pushes away the pre-existing air? Probably not. And I don't care either!
If 500 litres come from below and mix with the 10 litres existing, and no external air enters through the bubbler, I presume that the inside of the fermenter is basically free of oxygen.

I don't think anyone would deny that during very active fermentation, the strong flow of gas pushes the O2 (and any other gasses) out. LODO adherents (and others) use this phenomenon to purge their kegs during fermentation. But again, this isn't the "blanket" people are usually talking about. Maybe I should make (their) typical case for the blanket. Something like...

"CO2 is heavier than O2 and therefor settles in a "blanket" at the bottom of the headspace. So when you open a fermenter, O2 that enters the headspace is subsequently blocked from reaching the beer."

This is what blanket adherents usually mean. I know because I've been involved in these kinds of discussions for almost 15 years. And it's not true.
 
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Brooothru

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"...basically free of oxygen.." is probably a stretch. But "containing successively less and less air containing oxygen and greater and greater concentration of carbon dioxide" would likely be accurate.
 

Birrofilo

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Maybe I should make (their) typical case for the blanket. Something like...

"CO2 is heavier than O2 and therefor settles in a "blanket" at the bottom of the headspace. So when you open a fermenter, O2 that enters the headspace is subsequently blocked from reaching the beer."

This is what blanket adherents usually mean. I know because I've been involved in these kinds of discussions for almost 15 years. And it's not true.
And I agree it's not true. Just by opening the fermenter you create some whirlpool and you will disturb the gases inside.

I think the blanket proposition is valid if the two gases are not disturbed in any way and are confined into a closed container which is not shaken nor disturbed in any way.
 
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Jtvann

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And I agree it's not true. Just by opening the fermenter you create some whirlpool and you will disturb the gases inside.

I think the blanket proposition is valid if the two gases are not disturbed in any way and are confined into a closed container which is not shaken nor disturbed in any way.
Watch vikeman’s video above
 

Birrofilo

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Watch vikeman’s video above
The video above doesn't show what happens if you mix let's say bromine and nitrogen dioxide and then wait for several hours. I understand that gas initially mix, but I don't buy that they remain perfectly mixed forever.

If the theory is that gases just mix perfectly forever, than how do you explain that propane and butane pose a safety risk because they tend to accumulate near the ground? They are gases, and they are "heavier than air" as is the common expression, and they do dangerously accumulate on the ground. This is not an instantaneous phenomenon, it presumably takes hours, but it does happen (propane and butane are used in photography to preserve chemicals).

Scientific experiments are really nice and neat but one must not derive conclusions from them that they are not designed to demonstrate.

This experience shows how gas mix, not how they "separate" given enough time.
 
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BrewnWKopperKat

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The way to keep O2 out of beer is to keep fermenters closed and do closed transfers into thoroughly purged containers, via thoroughly purged tubing.
This would be another good topic for a "sticky".

This is what [some homebrewers] usually mean. I know because I've been involved in these kinds of discussions for almost 15 years. And it's not true.
This would be another good topic.
 
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