CO2 blanket poll

[TheMadKing]

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).

It isn't because air is disturbed by wind, it's because gasses mix homogeneously. The same effect will happen in a windless bubble full of air. If you inject LPG, it will initially fall and then eventually mix and remain mixed forever

 

[Konadog]

Constant source of CO2...

Exactly!

 

[10_degrees_play-doh]

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.

I'd say this is pretty much in line with my opinion- gas concentrations are different at different altitudes due to their densities, radon accumulates in basements, argon is suitable as welding shield gas, heavier than air gases are dangerous in confined spaces due to their tendency to displace atmospheric air. Air quality in confined spaces is a serious safety concern. All that being said, CO2 isn't all that heavy of a molecule compared to the rest of atmospheric air. Once you open your fermenter you're on borrowed time until the gas mixes. It's not instant, though. You can use the slightly heavier than air characteristic of CO2 to your advantage (not ruining a homebrew) as long as you don't treat it as magic.

 

[madscientist451]

I think the poll could include another question, does it matter if you use a CO2 blanket or not?
Then run some kind of experiment and see if people can pick out the different beer in a triangle test.
Beer #1 Fill the keg with star san and push it out w/CO2, push the beer out of the fermenter, with CO2 into the keg.
Beer#2 Don't purge the keg, but create a CO2 blanket in the bottom, push the beer out of the fermenter with CO2 but maintain a Co2 blanket over the top of the beer.
I'll go out on a limb and predict that initially, you won't be able to tell the difference, but after 3-4 months you may be able to pick out the different beer.

 

[BrewnWKopperKat]

@doug293cz , @Birrofilo - what if

• "we" were to pause this discussion
• allow the differing views (there may be more than two) time to create a "position" paper / statement
• post the "position" paper / statement to allow people to read the content (this implies that the topic containing the position paper would be locked and no discussion would be allowed until people read the different positions)
• then resume the discussion over in the brew science forum?

This approach may be a "product differentiator" for Homebrew Talk as it appears to me to be something that /rhomebrewing isn't structured to do.

It also allows for a well thought out position by each of the views.

Maybe the myth dies. Maybe it's not a myth under certain conditions that apply to homebrewing.

 

[doug293cz]

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).

Yes, I read the paper. It says nothing to support that mixed gases spontaneously "unmix" or stratify. The paper is all about showing how active air flow will dissipate a transient blob of a gas faster than without active airflow. Nothing surprising there.

What you see with dry ice is a water droplet (very fine mist) cloud. CO2 is invisible. Water droplets are orders of magnitude heavier than gas molecules, so they will stratify (until the water evaporates, and the water vapor mixes with the air.)

Brew on

 

[NewJersey]

We should send this to one of the myriad science TV shows that deal with myths

 

[Pappers_]

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.

Exactly, this is the crux of the question, and why the absolutist answers are not as helpful, perhaps. Its neither a myth nor an impermeable barrier. The answer to what is an unnacceptable amount of air will vary from brewer to brewer, process to process.

That being said, I appreciate these discussions and reminders of how little bits of our varied brewing practices can impact our beers.

 

[TheMadKing]

Exactly, this is the crux of the question, and why the absolutist answers are not as helpful, perhaps. Its neither a myth nor an impermeable barrier. The answer to what is an unnacceptable amount of air will vary from brewer to brewer, process to process.

That being said, I appreciate these discussions and reminders of how little bits of our varied brewing practices can impact our beers.

No argument.. And any reference to "you" is the collective "you" not you personally.

So this is a risk management question really. I've done some risk analysis and it's a crapchute IMO.

The only way to eliminate risk is to have an absolute stance. 99% of the time this isn't possible (like risks to your health, risks to your life, etc). In those cases the absolute elimination of risk is not possible while maintaining an acceptable quality of life.

In this case we are talking about risk of oxidation to your beer. Luckily for us, the absolute answers that "all cold side oxygen is bad" and "preventing all contact with air is the most efficient method of reducing the risk oxidation" are easy enough to achieve.

These things are possible with some basic process modifications that are not difficult or expensive or unachievable for most. If folks intentionally want to introduce risk to all of their beers because a minor process change or minor expense is not "worth it" to them, that's fine and that's their business. However, it is a fact that these process improvements will result in beer that is superior to descerning tasters.

For folks that are brewing for themselves and their friends, and can't taste any difference, cool, you do you. However I believe this forum is a place where (newer) brewers should be able to come to learn the practices that will result in the best possible product they can make. The argument that the "CO2 blanket" is sufficient protection is simply not the best practice and is just confusing to people who don't know any better.

Know the "right way" and then choose "Another way" with eyes open if it suits you, but don't teach others that the "right way" is pointless because it's not the way you do things.

 

[Dgallo]

I stand with @TheMadKing on this very sentiment. Our jobs as experienced brewers should be to provide insight to the best practices, based in both scientific and anecdotal evidence. It’s then up to the reader if they feel the additional steps, equipment, or practice is worth it to their level of engagement in this hobby. The science is gases do mix and the scientific evidence was provided. Ask any brewer of heavily hopped beers how well the co2 blanket theory works, and anecdotally they will provide the answer for you with muted character and darkening of color.

 

[BrewnWKopperKat]

These things are possible with some basic process modifications that are not difficult or expensive or unachievable for most.

In another topic, it was noted that one of the "problems" with homebrewing in 2020/2021 may be that there is "too much information" (or perhaps "too much discussion" or perhaps "too much debate").

Is there a single place where one can to go to read of those process modifications that you mentioned?

 

[TheMadKing]

In another topic, it was noted that one of the "problems" with homebrewing in 2020/2021 may bei that that there is "too much information" (or perhaps "too much discussion" or perhaps "too much debate").

Is there a single place where one can to go to read of those process modifications that you mentioned?

I'm not arguing that this forum should exclude everything but "best practice", that's not what I intended to imply.

But it should not be a place for debating whether scientific fact is true or not IMO.

This thread started with that very debate and has morphed into

"well yeah we all agree that the CO2 blanket is not real, but now we don't care"

That's totally fine.

But in this time and place it is really important to keep that line clear between questioning whether scientific facts are really true, or whether you acknowledge the facts and make a decision that is not aligned with the majority.

 

[BrewnWKopperKat]

Back in #65, I proposed the idea that the various "sides" could state their "position" for others to read/study/understand/contemplate.

So far, no response.

 

[chipmunk]

I think some of the issues/differences in opinion relate to the degree to which gravity acts on gasses at different densities.. And what is meant by “blanket”. Here‘s a you tube video that I found showing bromine gas both above and below the air.

Gravity acts on the gas and causes it “mix“ downwards by gravity even as if diffuses. Both processes happen at the same time.
So... it depends on what is meant by “blanket”. If you just dump a one time shot of CO2 into a keg and expect it to drop and sit there and 100% protect the beer from oxygen, then no, blankets don’t exist. However, if you are supplying a steady mass flow of CO2, next to the beer surface, and if the mass flow into the region above the beer exceeds the mass flow of CO2 out of the region, then the CO2 concentration will increase over time until it reaches equilibrium - which means all the gas in that volume is pure, So in this sense, yes, a CO2 blanket can exist.

 

[NGD]

I just use sulfurhexafloride when I bottle. Give my brews a nice zing

 

[day_trippr]

Wow.
Regardless, in the end it all comes down to this...

Cheers! ("News flash: Unbeatable phenomenon shreds blankets. Film at eleven" )

 

[VikeMan]

Regardless, in the end it all comes down to this...

Yep. And in reality, those molecules are very much smaller and more energetic. Even at 0 degrees C, O2 molecules for example move at about 500 meters per second. And those collisions are elastic. It's a Battle Royale with no winner, which gets more intense (energetic) at higher temps (which is what causes pressure to increase with increasing temperature as the molecules hit the walls more frequently).

 

[doug293cz]

I just use sulfurhexafloride when I bottle. Give my brews a nice zing

Why not uranium hexafluoride?

Brew on

 

[VikeMan]

I just use sulfurhexafloride when I bottle. Give my brews a nice zing

I used to, but it kept reacting with water to make stinky H2S, O2, and toothpaste.

 

[Konadog]

I used to, but it kept reacting with water to make stinky H2S, O2, and toothpaste.

So your breath smells like ass but your teeth are white?

 

[Beermeister32]

Here's some CO2 in action:

 

[Vale71]

Again, that's water mist from condensation of atmospheric vapor due to the extremely low temperature of dry ice. Water is:

1 - not a gas
2 - definitely heavier than air

which is why it tends to fall towards the ground (see rain for a practical example )

I think this discussion would improve greatly if it were based entirely on actual science instead of parlor tricks.

 

[Birrofilo]

It isn't because air is disturbed by wind, it's because gasses mix homogeneously. The same effect will happen in a windless bubble full of air. If you inject LPG, it will initially fall and then eventually mix and remain mixed forever

Well, the constant mantra here is that gases mix so fast that it is useless to even try to inject CO2 or LPG over a liquid, because it will not form a layer over the beer or the photographic chemical. An experiment was shown at the beginning of this thread which would have demonstrated that.

I contend this is not necessarily true, and that gases do form layers. I produced, for those who are ignorant of this basic facts of life, demonstration of the obvious, which is that LPG is dangerous because it does collect to the ground, and that there are laws in many countries to face the safety risk, and LPG is a gas. Anybody who lives in Italy knows that, some people don't even want LPG cars to be parked in a condominium garage because they are afraid.

Now you tell me that, in fact, yes, the layer will initially form, but that gases will mix subsequently.

Now my question is:

1) do you have any experiment, paper, document that convincingly proves that? Because if you say that based on the old theory of perfect gases, I think we already saw that doesn't apply.

2) When does "eventually" come, according to said paper? In the case of a layer of CO2 injected over beer, will they "eventually" mix after one day, two months, one hour?

In another thread it was shown by at least three homebrewers that filling the neck of the bottle with CO2 results in a much less oxydized beer, a beer which is very easily distinguishable either visually or in the taste test.

I am still waiting somebody who reconciles this empirical evidence with their theory based on gas equations that do not apply to the case in discussion, and do not apply to all gases at all.

Our discussion appears to live on two different levels: I bring forward real facts and others just wave their physics book, which has formulas which don't apply here and are not as universal as they think, as is proved by everyday experience.

 

[Dgallo]

Well, the constant mantra here is that gases mix so fast that it is useless to even try to inject CO2 or LPG over a liquid, because it will not form a layer over the beer or the photographic chemical. An experiment was shown at the beginning of this thread which would have demonstrated that.

I contend this is not necessarily true, and that gases do form layers. I produced, for those who are ignorant of this basic facts of life, demonstration of the obvious, which is that LPG is dangerous because it does collect to the ground, and that there are laws in many countries to face the safety risk, and LPG is a gas. Anybody who lives in Italy knows that, some people don't even want LPG cars to be parked in a condominium garage because they are afraid.

Now you tell me that, in fact, yes, the layer will initially form, but that gases will mix subsequently.

Now my question is:

1) do you have any experiment, paper, document that convincingly proves that? Because if it this the old theory of perfect gases, I think we already saw that doesn't apply?

2) When does "eventually" come, according to said paper? In the case of a layer of CO2 injected over beer, will they "eventually" mix after one day, two months, one hour?

In another thread it was shown by at least three homebrewers that filling the neck of the bottle with CO2 results in a much less oxydized beer, a beer which is very easily distinguishable either visually or in the taste test.

I am still waiting somebody who reconciles this empirical evidence with their theory based on gas equations that do not apply to the case in discussion, and do not apply to all gases at all.

Idk if anyone said instantaneous, maybe I missed that.

There has been plenty of evidence in this thread that shows the diffusion of gases. Under normal temperatures and pressure, these gases will not “settle” and separate again. Again diffusion does not happen immediately but let’s say you open your fermenter and the air that gets in will definitely diffuse within the day. Now the extent of air that got in, is more important. That is because diffusion WILL occur.

I fear you are trying to say unless someone can produce a specific paper that studies a specific interaction, then it can’t be true. However that a falsity in thinking because these are gas laws.

Depends on your math capabilities and understanding here, but here is a formula and chart for diffusion rate of gases

https://www.engineeringtoolbox.com/air-diffusion-coefficient-gas-mixture-temperature-d_2010.html

 

[BrewnWKopperKat]

These things are possible with some basic process modifications that are not difficult or expensive or unachievable for most.

In another topic, it was noted that one of the "problems" with homebrewing in 2020/2021 may be that there is "too much information" (or perhaps "too much discussion" or perhaps "too much debate").

Is there a single place where one can to go to read of those process modifications that you mentioned?

If not, this may be another idea for a "sticky".

 

[Clyde McCoy]

Well, the constant mantra here is that gases mix so fast that it is useless to even try to inject CO2 or LPG over a liquid, because it will not form a layer over the beer or the photographic chemical. An experiment was shown at the beginning of this thread which would have demonstrated that.

I contend this is not necessarily true, and that gases do form layers. I produced, for those who are ignorant of this basic facts of life, demonstration of the obvious, which is that LPG is dangerous because it does collect to the ground, and that there are laws in many countries to face the safety risk, and LPG is a gas. Anybody who lives in Italy knows that, some people don't even want LPG cars to be parked in a condominium garage because they are afraid.

Now you tell me that, in fact, yes, the layer will initially form, but that gases will mix subsequently.

Now my question is:

1) do you have any experiment, paper, document that convincingly proves that? Because if you say that based on the old theory of perfect gases, I think we already saw that doesn't apply.

2) When does "eventually" come, according to said paper? In the case of a layer of CO2 injected over beer, will they "eventually" mix after one day, two months, one hour?

In another thread it was shown by at least three homebrewers that filling the neck of the bottle with CO2 results in a much less oxydized beer, a beer which is very easily distinguishable either visually or in the taste test.

I am still waiting somebody who reconciles this empirical evidence with their theory based on gas equations that do not apply to the case in discussion, and do not apply to all gases at all.

Our discussion appears to live on two different levels: I bring forward real facts and others just wave their physics book, which has formulas which don't apply here and are not as universal as they think, as is proved by everyday experience.

Please, enough with this nonsense.

Did you ignore the video @VikeMan posted on the first page of this thread? It addresses all of your questions.



Re: "In another thread it was shown by at least three homebrewers that filling the neck of the bottle with CO2 results in a much less oxydized beer, a beer which is very easily distinguishable either visually or in the taste test."

Again, watch the video to get a sense for how quickly carbon dioxide gas diffuses into air. They show an example using nitrogen dioxide gas. It happens very quickly.

 

[jerrylotto]

I did read through all of the replies, but I will point out that open bucket fermentation is real. In a room withoit air movement and while fermentation is active, there is absolutely a blanket of CO2. As activity slows, the it gets thinner but as long as it is being produced, the layer exists. Once it stops, air will mix in but the impact is negligible. Only if you disturb the wort by adding dry hops or stirring will oxidation become a problem. That said - closed transfers and oxygen exclusion when handling beer is critical.

 

[Dgallo]

Our discussion appears to live on two different levels: I bring forward real facts and others just wave their physics book, which has formulas which don't apply here and are not as universal as they think, as is proved by everyday experience.

Again the experience you have is not an inclosed space such as a Fermenter. Also the LPG fumes would in fact complete diffuse in an closed room where the leak has stopped.

 

[Dgallo]

I did read through all of the replies, but I will point out that open bucket fermentation is real. In a room withoit air movement and while fermentation is active, there is absolutely a blanket of CO2. As activity slows, the it gets thinner but as long as it is being produced, the layer exists. Once it stops, air will mix in but the impact is negligible. Only if you disturb the wort by adding dry hops or stirring will oxidation become a problem. That said - closed transfers and oxygen exclusion when handling beer is critical.

Once fermentation stops the blanket is over

 

[Dgallo]

This is another thread I have to mark as ignore. Happy brewing everyone!