CO2 blanket poll

[Birrofilo]

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

https://www.ikegger.com/blogs/ikeggerworld/how-much-co2-is-produced-during-fermentation
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.

 

[VikeMan]

@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.

 

[Broothru]

"...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]

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.

 

[Jtvann]

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]

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.

 

[BrewnWKopperKat]

@IslandLizard: could @VikeMan and/or @Vale71 and/or others write a "sticky" on this (have posted it and then immediately lock it)?

In five years, maybe it will be like "Brewing Water Chemistry Primer" or maybe like "Dry Yeast FAQ".

 

[BrewnWKopperKat]

the real interest in an homebrewing forum is better beer.

Yup.

 

[BrewnWKopperKat]

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.

 

[day_trippr]

A sticky will not slay this myth....

 

[BrewnWKopperKat]

A sticky will not slay this myth....

"If you build it ([a sticky] and market it) they will come". There's a link button for the marketing step.

Plus helps reduce the need for large bold red letters.

 

[VikeMan]

I understand that gas initially mix, but I don't buy that they remain perfectly mixed forever.

The longer you wait, the more homogeneous the mixture. You can look at this as the fulfillment of Fick's Laws of Diffusion or as a manifestation of entropy. It's really both. Sorry to bring in a scientific explanation.

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.

They tend to "accumulate" near the ground because that's where the leaks are happening, near the ground. Stop the leak (which otherwise continues to refresh the dense part of the gradient) and give it time, and the gases will fill whatever space is available, homogeneously. The molecular weight of gases is basically trivial compared with their kinetic energies. There are noticeable "permanent gradients" influenced by molecular weights when you compare gas mixtures at sea level vs the edge of our atmosphere, but on the scales we experience, no.

 

[Vale71]

Guys, this is 18th Century physics, for crying out loud. The fact that adult, (presumably) educated people are actually having this discussion is simply appalling...
This really makes me sad and I'm not kidding.

 

[doug293cz]

...

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

Are you saying that you believe after gases spontaneously homogenize (mix completely), that after some period of time they then spontaneously separate? Can you provide any evidence (like a video showing them "unmixing" similar to the one that shows how they mix)?

Brew on

 

[Birrofilo]

They tend to "accumulate" near the ground because that's where the leaks are happening, near the ground. Stop the leak (which otherwise continues to refresh the dense part of the gradient) and give it time, and the gases will fill whatever space is available, homogeneously. The molecular weight of gases is basically trivial compared with their kinetic energies. There are noticeable "permanent gradients" influenced by molecular weights when you compare gas mixtures at sea level vs the edge of our atmosphere, but on the scales we experience, no.

No, absolutely not.
Propane, butane, propene and other gases, believe it or not, do accumulate to the ground because they are "heavier than air".

It is absolutely a given that LPG will accumulate on the "bottom" of the room or the container.
If you have a bottle and you fill it with LPG and air, the LPG will fall to the ground.

I am sure that you will be able to verify that with a quick search on the internet.

You can make an experiment: just close the windows in your basement, then open an LPG cylinder on the last steps of the staircase going to the basement, then remain on the upper floor.
You will feel the odour.

Now you light a lighter, while remaining on the upper floor: no explosion.

Then you throw the lighter on the basement (or anything incendiary) the your house will explode in a very spectacular way ;-)

The cylinder was almost on the ground floor, but the gas collected on the basement and that is why your house blew up.

Just ask anybody working with LPG or having a car going with LPG (5,6% of circulating cars in Italy, mine is one).

An LPG-car owner knows that he is forbidden to park on certain floors of a garage (garages which have a particular air circulation due to chemneys are exempted until -2 if memory serves). In normal garages an LPG car cannot be parked in an underground stage, whereas a methane car (CNG) can. Special parking places are reserved for LPG cars in parking lots with subterranean "grounds".

That is because CNG has a very different behaviour than LPG.

If you do a bit of searching around you will find this and I tell you this is physics, or if you prefer "real world physics".

For instance you can search for parking norms for LPG vehicles as opposed to parking norms for CNG vehicles.

Or just search for "propane heavier than air" etc. (or denser than air which is probably more correct, but people say "heavier").

EDIT: the different behaviour of LPG and natural gas is know to homebrewers who use LPG "turky friers" for their brewing needs. LPG accumulates on the ground where it can explode quite dramatically.

 

[Birrofilo]

Air is mostly CO2. Why isn’t all the CO2 on the ground with all the O2 way up high.
Because gases mix. Closed container or not, they mix.

Air is actually mostly nitrogen. CO2 is much less than 1%, 0,04% according to this source:
https://en.wikipedia.org/wiki/Atmosphere_of_Earthhttps://climate.nasa.gov/news/2491/10-interesting-things-about-air/
On the earth surface you have many motions of air due to temperature gradients: the sun doesn't heat all the Earth uniformly and you have several constant breezes, from sea to land and the other way round, from the mountains to the valley and the other way round, you have ascensional currents (used by sailplanes and birds to climb at high altitudes) and you have all sorts of winds. Air on the planet is continuously stirred.

 

[Birrofilo]

Are you saying that you believe after gases spontaneously homogenize (mix completely), that after some period of time they then spontaneously separate? Can you provide any evidence (like a video showing them "unmixing" similar to the one that shows how they mix)?

Brew on

No, I don't say "gases". I say "which gases?". Denser gases will tend to fall to the bottom in the long run, absent perturbation. Propane, butane, propene (and LPG in general) being a clear and undeniable example of this.

If you study the behaviour of those gases you see that they are just "heavy" (dense) and they do collect at the bottom, given time.

Now, again given time, I do expect let's say in a mixture of CO2 and O2 that the denser of the two collects at the bottom, if not perturbed. It certainly happens with propane and I don't see why it shouldn't happen with CO2, even if more slowly.

I think you are mislead by considering the equations for perfect gases (ideal gases) but perfect gases don't exist and many gases show a behaviour which is far from the behaviour of ideal gas.

 

[BrewnWKopperKat]

appalling

blanket adherents

flat earthers

Any chance the forum can "dail back" the hyperbole and labeling?

 

[Birrofilo]

Any chance the forum can "dail back" the hyperbole and labeling?

Absolutely. I also did not like the reference to "flat earthers".
Please keep the discussion civilized.

 

[Birrofilo]

This might be an interesting source to read about the behaviour of LPG, it also shows CO2 being denser than air

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6466308/
The entire paper is interesting and it shows interesting images. I suggest you read it all, it is not long or abstruse.

If LPG shows this behaviour in a few seconds, with a density of 2,46 kg/m3, vs. a density of air of 1,20 kg/m3, I don't see why CO2, with a density of 1,96 kg/m3 cannot sport this behaviour after an undefined number of hours.

@VikeMan

 

[NewJersey]

Why won't this myth just die already....

 

[doug293cz]

No, I don't say "gases". I say "which gases?". Denser gases will tend to fall to the bottom in the long run, absent perturbation. Propane, butane, propene (and LPG in general) being a clear and undeniable example of this.

If you study the behaviour of those gases you see that they are just "heavy" (dense) and they do collect at the bottom, given time.

Now, again given time, I do expect let's say in a mixture of CO2 and O2 that the denser of the two collects at the bottom, if not perturbed. It certainly happens with propane and I don't see why it shouldn't happen with CO2, even if more slowly.

I think you are mislead by considering the equations for perfect gases (ideal gases) but perfect gases don't exist and many gases show a behaviour which is far from the behaviour of ideal gas.

No, denser gases tend to collect in low spots in the short run. Given time, all gases homogenize. Collection in low spots occurs when the rate of release of the denser gas is faster than the rate of diffusion causing homogenization. An LPG leak is an example of high rate of release.

Look at the video again. They start with the dense gas on the bottom, and the lighter gas on the top. The dense gas then rises, and the lighter gas sinks. Short term there is stratification, long term there is homogenization.

Brew on

 

[Birrofilo]

No, denser gases tend to collect in low spots in the short run. Given time, all gases homogenize. Collection in low spots occurs when the rate of release of the denser gas is faster than the rate of diffusion causing homogenization. An LPG leak is an example of high rate of release.

Am I right in inferring that you did not read yet the document that I quoted in #51?

In the video, the denser gas is at the bottom at the beginning, it doesn't collect in low spots, and in the short run it mixes because the gas particles have this running behaviour.

But LPG does collect on the ground, from wherever you let it leak. If the ground is ventilated the gas is dispersed (because the air is disturbed by the "wind") if the ground is not ventilated the gas just sits on the floor and stays there. Even at 10 cm there is a much higher concentration than at 30 cm, as the paper shows experimentally, and "on the ground" there is more gas than at 10 cm. It really stratifies very much.

There is a picture where the behaviour of LPG is shown with some dry ice, which again has the same behaviour of LPG and sits in a very convincing way on the floor.

I don't ask you or anybody to "believe", but to understand the matter without preconceptions and prejudices. You might find that the laws of gas that you quote do not always apply in real world and in real situations (or in real bottle necks).

 

[TheMadKing]

This isn't something decided by popular opinion. It's a scientific fact. CO2 IS heavier than air, but gasses mix and the concept of a CO2 blanket is erroneous.

The only thing up for debate is how long it takes for CO2 to mix with an unacceptable amount of air in the size and shape of container you're using.

Good practice (being conservative) dictates that it happens instantly and you should do everything possible to minimize exposing a fermented beer to air.

 

[TheMadKing]

Are you saying that you believe after gases spontaneously homogenize (mix completely), that after some period of time they then spontaneously separate? Can you provide any evidence (like a video showing them "unmixing" similar to the one that shows how they mix)?

Brew on

Or that you're breathing pure argon and or radon right now?

 

[BrewnWKopperKat]

Good practice (being conservative) dictates that it happens instantly and you should do everything possible to minimize exposing a fermented beer to air.

... if one is getting oxidation related flavors in the beer.

 

[Konadog]

Don't trust a mixed gas blanket you can't see!

 

[TheMadKing]

... if you are getting oxidation related flavors in your beer.

Or That anyone who tastes your beer can perceive? Maybe you just don't notice it?

I happen to be one that is sensitive to oxidation flavors (and they are many and varied) the common descriptor of cardboard is only one and it is an indicator of severe oxidation. You can also get acetaldehyde (green apple), dulling of malt and hop flavors, loss of hop esters, etc

 

[TheMadKing]

Don't trust a mixed gas blanket you can't see!

View attachment 715608View attachment 715608

Constant source of CO2...

 

[BrewnWKopperKat]

I happen to be one that is sensitive to oxidation flavors (and they are many and varied) the common descriptor of cardboard is only one and it is an indicator of severe oxidation. You can also get acetaldehyde (green apple), dulling of malt and hop flavors, loss of hop esters, etc

No arguemet - everyone tastes beer differently (reference to study in The New IPA chapter 5).