Inert gas for purging kegs

[KiwiSander]

Hi all,

I normally use CO2 for purging kegs, usually while fermenting. And I assume this is the method used by all: I fill the keg with starsan, use the fermenter / CO2 tank to push out the starsan, leaving the tank filled with mostly CO2. But looking around the garage I also have Argon. I can't see any specific advantage in using argon, but would there be any disadvantage?

You would of course lose most (nearly all) of the argon when filling with beer, and then add CO2 for carbonating & serving. But even if some argon was left, would it matter? I'm thinking in a partial fill, if there was a layer of argon covering the beer the CO2 may never end up in solution? I don't think at serving pressure you would end up with significant argon in solution, but this may not be based on any real science.

I know there are various systems for keeping wine on argon to stop oxidation...

Sander

 

[AlexKay]

I also cannot see any advantage. The primary disadvantage would be price.

 

[KiwiSander]

Based on my understanding that argon is so much denser that it would actually stratify out:

For purging a keg, I think it may work, but no advantage.
For serving a fully carbonated beer - here I suppose it would insulate the beer in the keg, keeping it from oxidising, but that really isn't an issue with CO2 either.
In a fermenter is probably the place where it could be most beneficial, insulating the wort from oxygen, even when opening the fermenter / dry hopping etc. But again, I can't really find a problem that this would solve

 

[sibelman]

The idea of a blanket (stratification) of denser-than-air gas crops up again and again in spite of the objection that gasses freely and quickly mix. As far as I can tell from these discussions, the only sort of protective "blanket" that would meaningfully slow oxygen ingress is a non-gaseous barrier (e.g. a bottle cap or a LODO mash cap) or foam (as in "cap on foam").

Happy brewing!

 

[AlexKay]

Also, carbon dioxide is denser than argon.

 

[DuncB]

Purging the starsan with ferment gas and partially pressurising the keg whilst spunding the beer is free. Well researched and easy.
Argon will work but is more expensive for most users.
There won't be much argon in the keg once you've filled it with beer and put the CO2 on it in the kegerator.
I don't think it will interfere with the carbonation and I have no idea about argon solubility so can't say if Argonation would occur in your beer.
We know that nitrogen is not as soluble in beer as CO2.
Perhaps you could use it for stouts instead of nitrogen, but stout served with nitrogen needs a nitrogen and CO2 mix. Without this you lose the carbonation of the stout. So again not much help there.
Some might be concerned the argon isn't food safe as well not sure about this.
Is the argon usually for welding process?

 

[day_trippr]

I suspect if one does not flush the argon out of the keg head space that it would attenuate the rate of carbonation just by occupying some part of the surface area interface as well as the head space volume. But I put my faith on all things gas in @doug293cz, perhaps he will weigh in

Argon is used extensively in wine production so it must be benign - unless one huffs it and suffocates

Cheers!

 

[AlexKay]

Purging the starsan with ferment gas and partially pressurising the keg whilst spunding the beer is free. Well researched and easy.
Argon will work but is more expensive for most users.
There won't be much argon in the keg once you've filled it with beer and put the CO2 on it in the kegerator.
I don't think it will interfere with the carbonation and I have no idea about argon solubility so can't say if Argonation would occur in your beer.
We know that nitrogen is not as soluble in beer as CO2.
Perhaps you could use it for stouts instead of nitrogen, but stout served with nitrogen needs a nitrogen and CO2 mix. Without this you lose the carbonation of the stout. So again not much help there.
Some might be concerned the argon isn't food safe as well not sure about this.
Is the argon usually for welding process?

Argon is about twice as soluble in water as nitrogen, so still about 20 times less than CO2. An argon/CO2 mix pushing stout through a restrictor plate would give pretty similar results (lots of little, persistent bubbles that cascade down the outside of the glass) since this is just a function of solubility. On the other hand, nitrogen suppresses hop aroma and I don't know that the reasons for that are well understood, so anyone's guess as to what argon would do.

 

[doug293cz]

I suspect if one does not flush the argon out of the keg head space that it would attenuate the rate of carbonation just by occupying some part of the surface area interface as well as the head space volume. But I put my faith on all things gas in @doug293cz, perhaps he will weigh in

Argon is used extensively in wine production so it must be benign - unless one huffs it and suffocates

Cheers!

Any gas, other than CO2, in the headspace will reduce the CO2 partial pressure compared to the total absolute pressure. If you have 100% CO2 in the headspace at 12 psi gauge pressure, the CO2 partial pressure is 14.7 + 12 = 26.7 psia. It is the CO2 partial pressure, along with beer temp, that determines the carbonation level. If your headspace started with 100% argon at atmospheric pressure, and you then added CO2 to a gauge pressure of 12 psi, then the CO2 partial pressure is only 12 psia (and the argon partial pressure is 14.7 psia.) In the case starting with argon in the headspace, your carbonation level would be less than half what it would be if the headspace was 100% CO2.

Carbonation charts and calculators assume that the headspace is 100% CO2, unless they are specifically meant for mixed gases (and these are not commonly available.)

And as stated by several posters, gas stratification is a short term phenomenon, and lasts only a few minutes. All gases homogenize with each other in short order (unless you have a source of flowing gas.) There is no oxygen protection due to a heavier gas blanket, period.

Brew on

 

[KiwiSander]

Good point about partial pressure, didn't even think of that. And yes, my assumptions on stratification were just plain wrong That mostly came from using an Argon 'blanket' in welding to protect against oxygen, but that requires a constantly flooding gas, so not the same thing at all.

 

[sibelman]

Regarding food safety, argon is a noble gas and will not react with anything, so it seems completely safe.

 

[DuncB]

Regarding food safety, argon is a noble gas and will not react with anything, so it seems completely safe.

Provided it isn't contaminated when put in the cylinder with oil etc.

 

[day_trippr]

You could say that about any gas or blend we use with beer or wine...

Cheers!

 

[DuncB]

You could say that about any gas or blend we use with beer or wine...

Cheers!

I agree and I don't think everyone ( or many) use food grade gas. I just use what they refill my cylinder with.