The great nitrogen bubble debate

[choosybeggar]

Debate's over already? I expected a lot more resistance. ...and a lot more quotes from old books and marketing propaganda.

My feeling is that it's fairly obvious the conventional explanation doesn't fit that facts well. Until I began making nitro brews, though, I hadn't given it much thought.

 

[Yuri_Rage]

The concept is well explained in several posts, each with slightly different wording - that probably helps. Nice job with that. I was really happy to see the topic crop up.

 

[BrewKnurd]

My one concern about the argon experiment/argument is that it could be argued that the argon is replacing the nitrogen (I would bet you would get that, with no reasoning for it, from the the-bubbles-are-nitrogen crowd).

There would be about 3 times as much argon in solution than a comparable Nitrogen solution, so it should be three times as creamy with argon!

http://www.engineeringtoolbox.com/gases-solubility-water-d_1148.html

 

[Yuri_Rage]

Or just less effervescent, again proving the hypothesis set forth in this thread:

 

[choosybeggar]

The concept is well explained in several posts, each with slightly different wording - that probably helps. Nice job with that. I was really happy to see the topic crop up.

No problema. You owe me a beer though

 

[Mike37]

...marketing propaganda.

Nitro infused!!!!
Top secret gas blend!!!!
Cold brewed with nitrogen!!!!
Nitro filtered and served ice cold!!!!

Better?

 

[choosybeggar]

Nitro infused!!!!
Top secret gas blend!!!!
Cold brewed with nitrogen!!!!
Nitro filtered and served ice cold!!!!

Better?

And if the yeast came from a frozen stock, call it, "Nitro-Glycerine, really packs a wallop."

 

[RickFinsta]

Just saw this - you could do the bladder experiment with a Party Pig. Just throw a sparkler or stout faucet on there and if the head is thick and creamy, then debate=over.

 

[choosybeggar]

The bladder would need to generate sufficient pressure (~20 psi). It probably does not squeeze that much.

 

[RickFinsta]

The bladder would need to generate sufficient pressure (~20 psi). It probably does not squeeze that much.

You could always drill a hole and throw an air fitting on there; my point was simply that an apparatus for bladder testing already exists and is relatively cheap (much less than a beer engine!).

 

[choosybeggar]

So I checked out the Party Pig website:

The package requires no CO2 tanks or cartridges because it uses a self-inflating pressure pouch. As beer is dispensed from the PET plastic bottle through an attached push-button valve, the internal pressure pouch expands and maintains a constant 15-20 pounds per square inch of pressure. This is accomplished by combining citric acid and bicarbonate of soda in a controlled manner to produce CO2 gas, which remains inside the pressure pouch and does not come in contact with the beer.

Seems like just the ticket. Thanks.

 

[Mike37]

I see the party pig working just fine as long as the beer itself can be primed below 1.5 volumes.

Not saying it would be difficult, just that it's the key to this all working.

 

[techbrewie]

+1 to marketing for all of the misinformation out there.

At serving pressures (10-12psi for regular taps, 30psi for stout taps), a negligible amount of N is dissolved into the liquid. Beer is and always has been carbed with Co2, regardless of style or carbing method. This is because Co2 is the gas naturally created by yeast when bottling carbing.

The creamy head is a result of smaller Co2 bubbles created by the beer being forced through the restrictor plate of a stout tap. The smaller the surface area of any surface, the more stable it is. There are some physics equations that prove it somewhere, but im not going to get that sciency on you.

Now to push the beer through the restrictor plate you need a psi of around 30 psi (varying depending on the balance of your system) to get an acceptable rate of flow. If did it with just Co2, too much would be absorbed into your beer resulting in over carbed beer. This is corrected by mixing the Co2 with a gas that cannot be dissolved in liquid at those pressures(i.e. argon, nitrogen).

The sole purpose of nitrogen is to prevent over carbonation of your beer at the pressure required to push beer through the stout tap to create the desired mouthfeel and head for that style of beer.

When I get a little time I would be more that happy to post all of the equations and physics principles that support this, butchphr it might be a while before I can get to it. Nitrogen Sounds fancy and has been used as a catase by breweries (who should / do know better) to market their stouts and some porters.

Even if a beer was pushed on pure nitro across a long/thick enough beer line to support the pressures it would require to dissolve in beer, upon leaving the tap all of the nitro would surge out of the beer leaving you with nothing but foam.

 

[mattd2]

...Now to push the beer through the restrictor plate you need a psi of around 30 psi (varying depending on the balance of your system) to get an acceptable rate of flow. If did it with just Co2, too much would be absorbed into your beer resulting in over carbed beer. This is corrected by mixing the Co2 with a gas that cannot be dissolved in liquid at those pressures(i.e. argon, nitrogen)...

Is that 30 PSI at the keg or tap? From what I have seen it is at the keg and I have always had a theory the beergas might not even be needed for a "normal" homebrew setup. If the keg is hooked up with a short section of 1/4"/5/8" beerline then the normal ~15psi drop would not be present and you could serv on pure CO2 at a lower pressure and suitable temp to get the required pressure at the stout tap.

 

[Mike37]

Is that 30 PSI at the keg or tap? From what I have seen it is at the keg and I have always had a theory the beergas might not even be needed for a "normal" homebrew setup. If the keg is hooked up with a short section of 1/4"/5/8" beerline then the normal ~15psi drop would not be present and you could serv on pure CO2 at a lower pressure and suitable temp to get the required pressure at the stout tap.

That's 30 psi for a decently quick pour. 10 psi of co2 (or nitro, beer gas, etc.) will push beer through a short line and a stout faucet just fine, albeit slower than your typical nitro pour at 30 psi.

I have my keg set up exactly this way right now. At my keg's temperature, I can leave the regulator set at 8-10 and not worry about over carbonation.

 

[techbrewie]

that is a ballpark psi setting at the regulator. There could be a variance of + - 1-2 psi based on how you have your lines balanced (line diameter, line length, height distance from keg top to tap, carb volume etc.). Beer gas is not needed at all on a normal homebrew setup. It is only needed when you implement a stout tap.

As for your theory, it definitely merits an experiment. either it works or you end up with pure foam. Assuming it worked, you may run in to the problem of not having enough line to reach your taps if you go too short .

Most bars run everything on beer gas for the sake of using 1 gas and being able to push all types of beer. for me there is no place in town that fills beer gas, so no stout tap for me :-(

 

[Pratzie]

I was lead to believe that the Nitro is just to assist pushing the beer thru that restrictor plate in the faucet. That the pressure has to be greater then the CO2 alone but that the bubbles themselves are still CO2 that has been pushed thru the plate and has that cascading effect.


Guess im jumping on the pile here, sorry for not reading all the posts firsts

 

[mattd2]

...Beer gas is not needed at all on a normal homebrew setup. It is only needed when you implement a stout tap.

As for your theory, it definitely merits an experiment. either it works or you end up with pure foam. Assuming it worked, you may run in to the problem of not having enough line to reach your taps if you go too short ...

Sorry I meant normal homebrew setup with a stout tap. Looks like someone (Mike37) did experiement.

That's 30 psi for a decently quick pour. 10 psi of co2 (or nitro, beer gas, etc.) will push beer through a short line and a stout faucet just fine, albeit slower than your typical nitro pour at 30 psi.

I have my keg set up exactly this way right now. At my keg's temperature, I can leave the regulator set at 8-10 and not worry about over carbonation.

Thanks Mike, I have been wondering this for a while but don't have the cash to invest in a stout tap! now just to get this method out to more people!

 

[branCHEs]

So i think its fair to say that the debate is over. Nitro provides the pressure to push the beer through the restricter plate in a reasonable time with out over carbonating the beer. The actual bubbles are 100% CO2.

My only question: how does Guinness manage to achieve this cascading effect from their can? I believe Boddingtons English Pub Ale also manages to achieve this affect. I know the both have a little plastic ball inside of the can. I have been told that the balls are filled with nitrous and releases upon opening can.

 

[choosybeggar]

The devices generate a turbulent stream of beer on opening the can. In the sealed can, they are beer filled and at the same pressure as the contents of the can (well above atmospheric). Opening the can produces a dramatic pressure drop but the only way to relieve pressure within the widget is for gas and beer to shoot out of it's small hole, generating turbulent flow and CO2 foam.

 

[ajdelange]

The 'widget' has evolved appreciably over the years. The last one I looked at was about the size of a ping pong ball with a very small hole at one pole. These are, I assume, filled with nitrogen at atmospheric pressure before being dropped into the can. The can is then filled with beer and a little liquid N2 is squirted in the instant before the lid is clamped on. The can then goes into the pasteurizing tunnel where the heat causes the N2 to evaporate and the pressure becomes quite high so that the beer, at this higher pressure, is forced into the ball. The can is then sent off to the store, put in your refrigerator and eventually taken out. Even though it is now cold the partial pressure of nitrogen in there is a couple of atmospheres. When you open the can the pressure in the head space drops instantly to 1 atm but the pressure in the ball is still much higher than that as it can only bleed off through the tiny hole. In trying to equalize the pressure nitrogen and beer are forced out through the tiny hole. The widget is designed to spin as a result of this jet of beer. This jet of beer agitates the main volume of beer thus causing the CO2 in solution to come out in much the same way it does when the beer is agitated by being forced through a sparkler or restrictor plate.

 

[Scut_Monkey]

So I'm reviving this old thread. Did anyone ever go forward with the party pig/bladder testing? I'm going to buy a stout faucet and try running it on CO2 alone. It just doesn't make any sense to me to buy a Nitrogen tank and regulator when I won't be running a "nitrogen" beer that often. Just interested how many people have had success with a stout faucet with a low carbed keg running temporarily at a high pressure during serving. This seems to make sense to me and really shouldn't be a big pain in the butt to change the regulator for serving.

 

[ssgross]

So i'm reviving this once revived old thread because I think we can do much better.
I don't think there is a need, yet, for an experiment as this can all be proven mathematically, and any and all propaganda or articles without mathematical justification can be ignored. In particular, the wikipedia article for partial pressure
https://en.wikipedia.org/wiki/Partial_pressure
has most of the story.
The information needed is:
1) The properties by which nitrogen dissolves in a liquid is known (googlable), and quite negligible unless under extreeeeeeemly high pressures. There is a table on the wiki page for Henry's law that shows this. Co2 has medium solubility, which is why we can use it to make fizz, and nitrogen has very poor solubility.
Pure Speculation: diffusion may speed this up, just like using a stone to aerate your beer, or speed up force carbonation. I suspect this is how small amounts of nitrogen are dissolved into guinness at the factory, as claimed by the propaganda. This type of proprietary knowledge could be verified by an experiment. I liked the pH suggestion in a previous post.
2) The properties by which CO2 dissolve in a liquid are known, and most of us use some type of calculator for this.
3) The properties by which CO2 dissolves in nitrogen (and vice versa) are also known. In particular, co2 readily and easily dissolves in nitrogen
4) From the wiki: "Gases dissolve, diffuse, and react according to their partial pressures, and not according to their concentrations in gas mixtures or liquids." This behavior can be calculated using the formulae in the article.

Put it all together and I think we have the following answer. (Disclaimer: This is still speculation. I'm not a chemist..just a mathematician. I'll try to write this up as theorem and proof if I can find the time. Perhaps even a "how to" so the rest of the world can use their pocket calculators as more than a paper weight.)
1) Nitrogen's function in "beer gas" is solely to provide the added pressure to push through the restrictor plate WITHOUT over-carbonating the beer over time. This functionality can be achieved with any other gas that does not dissolve well, as pointed out by the argon experimenter posts.
2) The same results in pour can be achieved (there is a Brew Your Own article about this) by other means. Namely, crank up the co2 pressure, pour, lower the pressure, vent the keg.
3) it was claimed somewhere in this thread (EDIT: https://www.homebrewtalk.com/showthread.php?t=230229 post #5) that you could a) carbonate with co2, the b) hook up pure nitrogen and leave it with a perfect pour every time. This is a farce. Read the wiki again if you don't believe me. co2 readily dissolves in nitrogen. Thus, the pressure of pure nitrogen in the headspace does nothing to keep the co2 in solution. Only the partial pressure of co2 in the headspace does this. The partial pressure of co2 in solution will move to equilibrium with the head space, and the beer will go flat over time as co2 moves to the headspace. This is why beer gas has co2 in it, at the right partial pressure to maintain carbonation over time.
EDIT: or better yet, the first equation in the wiki shows that (in the headspace) as the volume of nitrogen increases with pints poured, the partial pressure of co2 decreases. Since co2 dissolves easily in nitrogen (this is dalton's law in the wiki), the beer goes flat.

In summary, I propose we develop a mathematical solution based on known chemistry, since none of us are privy to any proprietary information from guinness.

 

[ajdelange]

An engineer, a physicist and a mathematician walk into a bar....

The essential facts here are
1) CO2 is much more soluble in water/beer than N2
2) The solubility of CO2 is strongly dependent on temperature; the solubility of N2 isn't.
3) The size of the head in a mixed gas pour depends on the CO2 content
4) The bubbles formed with low Paco2 (partial pressure of CO2) are small
5) If PaN2 is appreciable the bubbles are more stable because the N2 diffuses back into solution more slowly than CO2 does
6)The smaller bubbles give less physical 'prick' on the tongue when they burst.
7)A bubble filled partially with nitrogen gives less carbonic acid 'prick' than a pure CO2 bubble.

The equilibrium equation for the mix of CO2 and Nitrogen as applied to the particular problem of interest can be found in Carroll, T. C. N., The effect of dissolved nitrogen on foam and palate, MBAA TQ, Vol 16, No. 3 1979

It is indeed impossible to mimic the performance of a mixed gas system with nitrogen alone as the beer will go flat (PaCO2 in pure N2 is 0) but it is possible to get a pretty good approximation with pure CO2. One keeps the beer under enough pressure to keep it at 1.2 - 1.5 volumes at the storage temperature then raises the pressure to 20 - 25 psig for serving (i.e. high enough to let the sparkle plate do its job) and then reduces it again at the conclusion of serving. This is clearly not possible if you want your stout 'on tap' but is OK if you are only going to serve it say 1 day a week. I, and several other people have done this. It's not exactly the same but it is pretty close.

 

[mattd2]

An engineer, a physicist and a mathematician walk into a bar....

The essential facts here are
1) CO2 is much more soluble in water/beer than N2
2) The solubility of CO2 is strongly dependent on temperature; the solubility of N2 isn't.
3) The size of the head in a mixed gas pour depends on the CO2 content
4) The bubbles formed with low Paco2 (partial pressure of CO2) are small
5) If PaN2 is appreciable the bubbles are more stable because the N2 diffuses back into solution more slowly than CO2 does
6)The smaller bubbles give less physical 'prick' on the tongue when they burst.
7)A bubble filled partially with nitrogen gives less carbonic acid 'prick' than a pure CO2 bubble.

The equilibrium equation for the mix of CO2 and Nitrogen as applied to the particular problem of interest can be found in Carroll, T. C. N., The effect of dissolved nitrogen on foam and palate, MBAA TQ, Vol 16, No. 3 1979

It is indeed impossible to mimic the performance of a mixed gas system with nitrogen alone as the beer will go flat (PaCO2 in pure N2 is 0) but it is possible to get a pretty good approximation with pure CO2. One keeps the beer under enough pressure to keep it at 1.2 - 1.5 volumes at the storage temperature then raises the pressure to 20 - 25 psig for serving (i.e. high enough to let the sparkle plate do its job) and then reduces it again at the conclusion of serving. This is clearly not possible if you want your stout 'on tap' but is OK if you are only going to serve it say 1 day a week. I, and several other people have done this. It's not exactly the same but it is pretty close.

A marketer and an accountant join them; The accountant says "Hey guys, I think your on to something - we could charge people extra for this"
And the Marketer adds "Yeah, but I think the general public will probably get confused with all you science talk - so let's just say the nitrogen makes smaller bubbles and that's what gives it the creamy texture"

And I think that has now gone full circle back to the beginning of this thread

On a serious scientific note though - would it be possible to overcarb the beer on CO2, then pressurise to 30PSI with N2, and if you calculate it correctly end up with the right mix once it all equilibrulisese (word?)... that is if you have enough time/patience

 

[doug293cz]

...

On a serious scientific note though - would it be possible to overcarb the beer on CO2, then pressurise to 30PSI with N2, and if you calculate it correctly end up with the right mix once it all equilibrulisese (word?)... that is if you have enough time/patience

No. You could do it for the initial keg volume, but then as the keg empties, it will take more and more CO2 in the headspace to stay in equilibrium with the carbonation in the beer. So more and more CO2 will diffuse out of the beer, reducing the carbonation level.

Brew on

 

[ajdelange]

On a serious scientific note though - would it be possible to overcarb the beer on CO2, then pressurise to 30PSI with N2, and if you calculate it correctly end up with the right mix once it all equilibrulisese (word?)... that is if you have enough time/patience

Yes and that is actually how Guiness got to the nitrogen thing. In the 1940's they were selling Guiness in an 11 gal keg with 8 gal beer (not completely fermented) and the head space pressurized to 3.5 atm (absolute) with air. They later replaced the air with pure nitrogen (to discourage bacterial growth according to Carroll) "..which led to the discovery of the dramatic effect of small amounts of dissolved nitrogen gas on head creaminess and durability."

As has been observed, the situation will change as the beer is drawn off but evidently the 3:8 initial ratio of gas to beer is adequate to deliver acceptable product from first to last glass.

Thus you don't actually have to calculate it. Guiness has already done that for you. Carbonate to 1.5 vols then pressurize to 3.5 atm absolute with nitrogen and you should be there.

 

[Wrekked]

_

 

[55x11]

An engineer, a physicist and a mathematician walk into a bar....

The essential facts here are
1) CO2 is much more soluble in water/beer than N2
2) The solubility of CO2 is strongly dependent on temperature; the solubility of N2 isn't.
3) The size of the head in a mixed gas pour depends on the CO2 content
4) The bubbles formed with low Paco2 (partial pressure of CO2) are small
5) If PaN2 is appreciable the bubbles are more stable because the N2 diffuses back into solution more slowly than CO2 does
6)The smaller bubbles give less physical 'prick' on the tongue when they burst.
7)A bubble filled partially with nitrogen gives less carbonic acid 'prick' than a pure CO2 bubble.

The equilibrium equation for the mix of CO2 and Nitrogen as applied to the particular problem of interest can be found in Carroll, T. C. N., The effect of dissolved nitrogen on foam and palate, MBAA TQ, Vol 16, No. 3 1979

It is indeed impossible to mimic the performance of a mixed gas system with nitrogen alone as the beer will go flat (PaCO2 in pure N2 is 0) but it is possible to get a pretty good approximation with pure CO2. One keeps the beer under enough pressure to keep it at 1.2 - 1.5 volumes at the storage temperature then raises the pressure to 20 - 25 psig for serving (i.e. high enough to let the sparkle plate do its job) and then reduces it again at the conclusion of serving. This is clearly not possible if you want your stout 'on tap' but is OK if you are only going to serve it say 1 day a week. I, and several other people have done this. It's not exactly the same but it is pretty close.

actually both CO2 and N2 solubility depends on temperature similarly - with a drop of 2.5-3 from 0C to 40C. Overall CO2 is about 100 times more soluble than N2 (3g/L for CO2 and 0.03 g/L for N2).

http://www.engineeringtoolbox.com/gases-solubility-water-d_1148.html

This means that bubbles in your beer are almost entirely CO2 (99% or maybe 97% - depending on gas composition and level of saturation reached).

I doubt that 1% Nitrogen content inside the bubbles contributes to significant reduction of carbonic bite.
I believe Nitrogen contribution in bubbles is irrelevant to the taste - you just need to create small bubbles by applying high pressure and forcing lightly carbed beer through an aperture. The "smooth" taste is simply result of those small bubbles. You can push lightly carbed beer with other gases, or mechanical devices and get the precisely same effect.

 

[doug293cz]

actually both CO2 and N2 solubility depends on temperature similarly - with a drop of 2.5-3 from 0C to 40C. Overall CO2 is about 100 times more soluble than N2 (3g/L for CO2 and 0.03 g/L for N2).

http://www.engineeringtoolbox.com/gases-solubility-water-d_1148.html

This means that bubbles in your beer are almost entirely CO2 (99% or maybe 97% - depending on gas composition and level of saturation reached).

I doubt that 1% Nitrogen content inside the bubbles contributes to significant reduction of carbonic bite.
I believe Nitrogen contribution in bubbles is irrelevant to the taste - you just need to create small bubbles by applying high pressure and forcing lightly carbed beer through an aperture. The "smooth" taste is simply result of those small bubbles. You can push lightly carbed beer with other gases, or mechanical devices and get the precisely same effect.

Since a typical beer gas is 25% CO2 & 75% N2, the N2 partial pressure will be 3X the CO2 partial pressure. Thus you will get about 3 parts N2 to 100 parts CO2. Still not much nitrogen in those bubbles.

Brew on