Can we dispel the myth of the 'CO2 Blanket' ?

[Zadkiel]

I see it so often repeated here.

In just the last 2 days I've seen 4 separate posts (and I don't read every thread, so there's probably more I missed) from people talking about how when opening a fermenter, there exists some sort of 'CO2 blanket' that protects your brew.

I'm sorry, but gas doesn't work that way. Convection and molecular diffusion of gasses between different concentration levels takes place almost instantly.

If CO2 somehow sinks to the bottom then we'd all be dead thanks to living in a CO2 blanket covering the planet. It doesn't work that way.

In reality, a 100% concentration of CO2 being exposed to a convecting atmosphere of 0.04% CO2 will diffuse in milliseconds, a few seconds at the outside. Likewise a 21% concentration of O2 being exposed to a bucket containing 0% O2 will likewise diffuse in milliseconds/seconds. Pressure differences, temperature differences and convection currents in the air all act to accelerate that process.

I've seen it argued that you can see the CO2 blanket from a dry ice (frozen/liquid CO2) machine - CO2 is colorless, you cannot 'see' it, what you see from a dry ice machine is condensation of water vapour in the air caused by the temperature difference between the rapidly expanding cooler gas and the air in the room, which then does drop down towards the floor and as it reaches higher concentrations, becomes visible. The white cloud is water, not CO2.

 

[BrewnWKopperKat]

Can we dispel the myth of the 'CO2 Blanket' ?

No.

Related question

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Can we stop posting text that is statistically generated?​

​

 

[Zadkiel]

Can we stop posting text that is statistically generated?

Really not 100% sure what you mean by that, as nothing in my post had anything at all to do with statistics, but if you mean what I think you mean, then sure, I'll remove it. It was only there to support my argument, not as primary evidence, so I've no issue removing it, it changes nothing.

 

[BrewnWKopperKat]

 

[Cheshire Cat]

I see it so often repeated here.

In just the last 2 days I've seen 4 separate posts (and I don't read every thread, so there's probably more I missed) from people talking about how when opening a fermenter, there exists some sort of 'CO2 blanket' that protects your brew.

I'm sorry, but gas doesn't work that way. Convection and molecular diffusion of gasses between different concentration levels takes place almost instantly.

If CO2 somehow sinks to the bottom then we'd all be dead thanks to living in a CO2 blanket covering the planet. It doesn't work that way.

In reality, a 100% concentration of CO2 being exposed to a convecting atmosphere of 0.04% CO2 will diffuse in milliseconds, a few seconds at the outside. Likewise a 21% concentration of O2 being exposed to a bucket containing 0% O2 will likewise diffuse in milliseconds/seconds. Pressure differences, temperature differences and convection currents in the air all act to accelerate that process.

I've seen it argued that you can see the CO2 blanket from a dry ice (frozen/liquid CO2) machine - CO2 is colorless, you cannot 'see' it, what you see from a dry ice machine is condensation of water vapour in the air caused by the temperature difference between the rapidly expanding cooler gas and the air in the room, which then does drop down towards the floor and as it reaches higher concentrations, becomes visible. The white cloud is water, not CO2.

Look in this modern age we should be discussing the CO2 Duvet.

 

[fluketamer]

it took me a while to figure out this thread. im slow.

i read an article a few days ago that referenced "the blanket" . i think i saw a post a few days ago too. i think i saw it said that air is mostly nitrogen so the amount of o2 is even lower than one would think.

its prolly likely, that in a very heavily dry hopped beer like 2 plus oz per gallon, the small amount of oxygen that gets into a fermenter during old timey dry hopping methods is eonugh to be a significant problem. i havent done a side by side test. i am sure brulosophy will have a similar experiment with useless statistical value. but i have immediately noticed the diffrence in hop preservation when i limited my o2 exposure as much as i can , even on low hop dosing rates.

i think when it was standard to just open the bucket and throw em in, nobody was using such huge dry hopping rates and it prolly didnt really matter.

i think the blanket idea is for those of us who havent made the jump to fully oxygen free dry hopping ( myself included) to rationalize there process. i think people who rely on and post about the blanket dont have pressure fermenting ca[abilities. but its just speculation.

btw, i didnt use any AI in generating ( lol) this post.

 

[mashdar]

Dispelled multiple tumes over the decades. Won't die.
https://www.homebrewtalk.com/threads/the-protective-co2-blanket.303980/

 

[Beekeeper]

A fluffy, frothy krausen is what I might consider a protective CO2 blanket.

But my fermenter(s) stay closed to the atmosphere once fermentation has begun.

 

[BrewnWKopperKat]

Dispelled multiple tumes over the decades. Won't die.

It's one of a number of topics that will keep coming back ...

... as long as there are new brewers coming to discussion forums.

 

[Zadkiel]

i read an article a few days ago that referenced "the blanket" . i think i saw a post a few days ago too. i think i saw it said that air is mostly nitrogen so the amount of o2 is even lower than one would think.

Nitrogen levels don't matter, what matters most is the concentration difference in CO2 in the fermenter (hopefully close to 100%) and the concentration in the air surrounding it (CO2 at ground level is approx 0.04% - used to be 0.02%) that huge difference causes diffusion to happen extremely rapidly. If there was little to no convection happening, then diffusion might happen over the course of seconds, but in the presence of any convection (which happens naturally within your house, you're unaware of it but the air in your house is under a constant state of convection) it will take milliseconds. In the opposite direction, the 21% concentration of O2 in the air will diffuse rapidly into the 0% (or as close to it as makes no difference) O2 inside the bucket.

A fermenter with a narrow neck, or a small opening, will reduce the effect of convection to some extent. Not prevent, just reduce (popping off an airlock for a few seconds isn't going to let much in). It won't prevent diffusion, but it will take longer to reach full saturation, maybe even long enough that if you're quick enough it won't reach full 21% O2 inside, but I most commonly see the 'CO2 Blanket' being used giving advice to new brewers using plastic buckets, and if you're taking the lid off a bucket, before the lid has even been removed, the gas inside will be mixed to atmospheric levels, it's just simply not true.

 

[Zadkiel]

Look in this modern age we should be discussing the CO2 Duvet.

Nooo, duvets are warmer, and diffusion happens quicker at higher temperatures, a CO2 Duvet would vanish much faster than a CO2 blanket would!

 

[mac_1103]

I see it so often repeated here.

And immediately debunked every time. We can only do so much.