### Author Topic: Gas permeability of a liquid  (Read 432 times)

#### HopDen

• Brewmaster
• Posts: 675
##### Gas permeability of a liquid
« on: November 15, 2021, 05:21:20 pm »
I have a 5 gallon keg of an imperial stout that was 10.5% abs before an 11 month hiatus in a barrel. I had it on gas @ 30psi for 2 days and it is barely carbonated. I checked all fittings for leaks, none found. Back on gas @ 30psi for another 2 days, very little carbonation at all. Checked fittings again, no leaks found. Does the viscosity of a liquid impede the absorption of the Co2?

#### RC

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• Posts: 614
##### Re: Gas permeability of a liquid
« Reply #1 on: November 15, 2021, 05:43:19 pm »
What is the temp of the beer? And how full is the keg?

#### HopDen

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• Posts: 675
##### Re: Gas permeability of a liquid
« Reply #2 on: November 15, 2021, 06:14:42 pm »
What is the temp of the beer? And how full is the keg?

38* and full keg minus 1 quart

#### RC

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##### Re: Gas permeability of a liquid
« Reply #3 on: November 15, 2021, 06:36:58 pm »
If the end of the gas-in tube is submerged, and it might be given that liquid level, then the head space in that keg is only the diameter of the dip tube. You may need to bleed more beer out of the keg so that the beer level is below the gas-in dip tube.

#### kramerog

• Brewmaster General
• Posts: 2196
##### Re: Gas permeability of a liquid
« Reply #4 on: November 15, 2021, 09:26:25 pm »
Does the viscosity of a liquid impede the absorption of the Co2?

Yes because the diffusion coefficient is inversely proportional to viscosity. RC may be right that the bottom of the gas-in tube is submerged.

#### HopDen

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• Posts: 675
##### Re: Gas permeability of a liquid
« Reply #5 on: November 16, 2021, 04:32:56 am »
Does the viscosity of a liquid impede the absorption of the Co2?

Yes because the diffusion coefficient is inversely proportional to viscosity. RC may be right that the bottom of the gas-in tube is submerged.

Thanks! I will learn what diffusion coefficient is this afternoon. Not so certain about gas dip tube submerged in liquid though. All of my beers are kegged until the beer runs out of the gas tube blow off. Im not saying that is incorrect but my experience has not shown that.

#### narvin

• I spend way too much time on the AHA forum
• Posts: 2620
##### Re: Gas permeability of a liquid
« Reply #6 on: November 16, 2021, 05:56:26 pm »
If the end of the gas-in tube is submerged, and it might be given that liquid level, then the head space in that keg is only the diameter of the dip tube. You may need to bleed more beer out of the keg so that the beer level is below the gas-in dip tube.

Pressure of the CO2 from the regulator and the gas in the head space should equalize immediately, regardless of whether the tube is exposed, and the surface area exposed to gas would be the same.  People carbonate with gas going in through the liquid dip tube and have no problems

#### RC

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##### Re: Gas permeability of a liquid
« Reply #7 on: November 16, 2021, 06:59:58 pm »
If the end of the gas-in tube is submerged, and it might be given that liquid level, then the head space in that keg is only the diameter of the dip tube. You may need to bleed more beer out of the keg so that the beer level is below the gas-in dip tube.

Pressure of the CO2 from the regulator and the gas in the head space should equalize immediately, regardless of whether the tube is exposed, and the surface area exposed to gas would be the same.  People carbonate with gas going in through the liquid dip tube and have no problems

Are you arguing that the head space of a keg does not affect forced carbonation?

#### narvin

• I spend way too much time on the AHA forum
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##### Re: Gas permeability of a liquid
« Reply #8 on: November 16, 2021, 07:04:19 pm »
If the end of the gas-in tube is submerged, and it might be given that liquid level, then the head space in that keg is only the diameter of the dip tube. You may need to bleed more beer out of the keg so that the beer level is below the gas-in dip tube.

Pressure of the CO2 from the regulator and the gas in the head space should equalize immediately, regardless of whether the tube is exposed, and the surface area exposed to gas would be the same.  People carbonate with gas going in through the liquid dip tube and have no problems

Are you arguing that the head space of a keg does not affect forced carbonation?

No.  The gas dip tube extends down an inch or so? So are you arguing that even with head space of an inch, the dip tube being submerged negates that?

#### RC

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• Posts: 614
##### Re: Gas permeability of a liquid
« Reply #9 on: November 16, 2021, 07:48:19 pm »
I am not sure I understand what you are saying, but yes, I think is what I am arguing. I think.

Head space is the "open air" space in a keg where gas/atmosphere resides. If the gas-in tube, ~8mm diameter, is below the liquid, and this is where the CO2 is pushing, then the surface area of the head space in the keg is effectively the diameter of the dip tube.

The diameter of a corny keg is 203mm. The same pressure of CO2 pressing down on a surface area of 8mm vs. 203mm will push a lesser amount of CO2 per unit time into the beer. Hence a longer carb time.

Unless I am missing something...?

#### jeffy

• Official Poobah of No Life. (I Got Ban Hammered by Drew)
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• Tampa, Fl
##### Re: Gas permeability of a liquid
« Reply #10 on: November 17, 2021, 06:02:26 am »
I am not sure I understand what you are saying, but yes, I think is what I am arguing. I think.

Head space is the "open air" space in a keg where gas/atmosphere resides. If the gas-in tube, ~8mm diameter, is below the liquid, and this is where the CO2 is pushing, then the surface area of the head space in the keg is effectively the diameter of the dip tube.

The diameter of a corny keg is 203mm. The same pressure of CO2 pressing down on a surface area of 8mm vs. 203mm will push a lesser amount of CO2 per unit time into the beer. Hence a longer carb time.

Unless I am missing something...?
I'm no scientist, but that makes no sense.  The gas goes through the dip tube and ends up in the head space.
Jeff Gladish, Tampa (989.3, 175.1 Apparent Rennarian)
Homebrewing since 1990
AHA member since 1991, now a lifetime member
BJCP judge since 1995

#### narvin

• I spend way too much time on the AHA forum
• Posts: 2620
##### Re: Gas permeability of a liquid
« Reply #11 on: November 17, 2021, 07:34:47 am »
I am not sure I understand what you are saying, but yes, I think is what I am arguing. I think.

Head space is the "open air" space in a keg where gas/atmosphere resides. If the gas-in tube, ~8mm diameter, is below the liquid, and this is where the CO2 is pushing, then the surface area of the head space in the keg is effectively the diameter of the dip tube.

The diameter of a corny keg is 203mm. The same pressure of CO2 pressing down on a surface area of 8mm vs. 203mm will push a lesser amount of CO2 per unit time into the beer. Hence a longer carb time.

Unless I am missing something...?
I'm no scientist, but that makes no sense.  The gas goes through the dip tube and ends up in the head space.

Exactly.  Otherwise you could open the lid without more gas going in to the keg.

#### RC

• Brewmaster
• Posts: 614
##### Re: Gas permeability of a liquid
« Reply #12 on: November 17, 2021, 10:13:36 am »
OK I see the error of my ways now. A momentary (hopefully just momentary!) lapse of reason. I guess I should stick to biology!

#### Saccharomyces

• Senior Brewmaster
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• Deus ex machina
##### Re: Gas permeability of a liquid
« Reply #13 on: November 24, 2021, 03:47:18 pm »
Yes because the diffusion coefficient is inversely proportional to viscosity. RC may be right that the bottom of the gas-in tube is submerged.

Bingo! Gas diffusion becomes increasing more difficult as the density of a liquid increases.  It is the major reason why we need to pitch more viable yeast cells in higher density worts (the other reasons being the higher osmotic pressure being hard on cell all turgor pressure and higher ABV being more toxic to yeast cell heath).