Failing to Obtain Keg Carbonation in Beer

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Berube05734

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Good Morning, All,

First time posting. :)

I've been brewing (all grain) for the last year and have finally graduated to kegging my beer. I finally got tired of seeing my hard work quickly turn as brown as the bottle it's sitting in - as well as that dreaded wet cardboard flavor after just 3 weeks. I bought a couple of corny kegs and a mini-fridge which I converted into a kegerator.

So, I'm struggling with obtaining full carbonation in the beer. I'm ending up with mile high foam on top, but after the first sip (which tastes/feels carbonated), the beer starts to quickly go flat. I've spent weeks scouring sites/forums for tips and methods of carbing the beer, but I'm still doing something wrong or missing a step.

I attempted a closed transfer system - star san'd the keg, purged the sanitizer from the keg...stopped purging when I got nothing but air and residual bubbles coming out the beer line. Then I used my CO to push the beer from the fermenter into the keg (this, I was absolutely tickled about as it worked so slick). I set the CO pressure to 40 and let it sit for a couple of days and then backed it down to 12.5 and let it sit for a week. Right up to the last glass, I continued to get 4" of foam and flat beer after the first couple of sips.

How do I move that CO that's creating all that foam into the beer itself? The only thing that I haven't tried is using a longer beer line. My LHBS cut me 4' and said I'd be fine. However, a lot of forums contradict this and if I use some of the formulas online to calculate the length of the beer line I should use, my calculations arrive at 10'.

How does the length of the beer line affect carbonation in the beer...that, I'm not understanding...

Secondly, although I was ecstatic to see that the color remained true throughout the entire time, a very lovely peachy hazy color,...as I got towards the bottom of the keg I started to detect a bit of cardboard. Is it possible to still have a layer of oxygen in the keg while being fully pressurized? If so, is there an obvious way to know when all oxygen has been purged from the keg?

Thanks,

Pam
 

TheMadKing

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Good Morning, All,

First time posting. :)

I've been brewing (all grain) for the last year and have finally graduated to kegging my beer. I finally got tired of seeing my hard work quickly turn as brown as the bottle it's sitting in - as well as that dreaded wet cardboard flavor after just 3 weeks. I bought a couple of corny kegs and a mini-fridge which I converted into a kegerator.

So, I'm struggling with obtaining full carbonation in the beer. I'm ending up with mile high foam on top, but after the first sip (which tastes/feels carbonated), the beer starts to quickly go flat. I've spent weeks scouring sites/forums for tips and methods of carbing the beer, but I'm still doing something wrong or missing a step.

I attempted a closed transfer system - star san'd the keg, purged the sanitizer from the keg...stopped purging when I got nothing but air and residual bubbles coming out the beer line. Then I used my CO to push the beer from the fermenter into the keg (this, I was absolutely tickled about as it worked so slick). I set the CO pressure to 40 and let it sit for a couple of days and then backed it down to 12.5 and let it sit for a week. Right up to the last glass, I continued to get 4" of foam and flat beer after the first couple of sips.

How do I move that CO that's creating all that foam into the beer itself? The only thing that I haven't tried is using a longer beer line. My LHBS cut me 4' and said I'd be fine. However, a lot of forums contradict this and if I use some of the formulas online to calculate the length of the beer line I should use, my calculations arrive at 10'.

How does the length of the beer line affect carbonation in the beer...that, I'm not understanding...

Secondly, although I was ecstatic to see that the color remained true throughout the entire time, a very lovely peachy hazy color,...as I got towards the bottom of the keg I started to detect a bit of cardboard. Is it possible to still have a layer of oxygen in the keg while being fully pressurized? If so, is there an obvious way to know when all oxygen has been purged from the keg?

Thanks,

Pam
Hey Pam welcome to the forum!

So first of all it sounds like you're doing almost everything right and that your beer is fully carbonated (maybe a touch low, but not bad). What I think is probably happening is that your short keg line is allowing the CO2 to come out of the beer too quickly as it pours into your glass and you are losing most of your carbonation when you pour. The reason why this happens is because the inside of your beer line provides resistance (friction) which pushes against the pressure created against the carbonation in your beer. This slows down the pressure transition from high pressure to low pressure and makes the carbonation stay in the beer better. A short line makes a shorter transition and more foam, while a long line makes a slower pour and a more gentle transition. This is a similar concept to when you take the bottle cap off a soda quickly and it foams up, whereas if you take the cap off very slowly it won't foam as much.

One piece of information that you didn't mention, what temperature is the beer coming out of your tap?
A second piece of information is what temperature is your kegerator set to?

If you have poor air circulation inside your kegerator and the top of your keg and your serving line is warm and the bottom of your keg is cold that will make foamy pours even worse.

The keys to keeping carbonation in your beer are:
  • Keep it cold (38-42 degrees is my preferred range).
  • Keep your keg pressurized to the appropriate serving pressure based on the temperature you set. https://www.kegoutlet.com/media/uploads_ckeditor/Carbonatin-Chart.jpg this carbonation chart helps you determine the correct serving pressure for your keg pressure.
  • Use approximately 1 foot of 3/16" ID beverage tubing per 1 PSI of carbonation pressure. So 10' should get you pretty close
  • Make sure you're pouring into clean glassware

As for your oxidation question, there are a million ways that oxygen can get into your beer, but purging liquid out of your keg with CO2 is a great step at reducing oxidation. But if you are fermenting in a bucket and take the lid off to transfer then you are introducing oxygen. The goal should be to never ever let your beer contact air (at all) after fermentation begins. And that's very difficult to achieve.
 
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Berube05734

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Hey Pam welcome to the forum!

So first of all it sounds like you're doing almost everything right and that your beer is fully carbonated (maybe a touch low, but not bad). What I think is probably happening is that your short keg line is allowing the CO2 to come out of the beer too quickly as it pours into your glass and you are losing most of your carbonation when you pour. The reason why this happens is because the inside of your beer line provides resistance (friction) which pushes against the pressure created against the carbonation in your beer. This slows down the pressure transition from high pressure to low pressure and makes the carbonation stay in the beer better. A short line makes a shorter transition and more foam, while a long line makes a slower pour and a more gentle transition. This is a similar concept to when you take the bottle cap off a soda quickly and it foams up, whereas if you take the cap off very slowly it won't foam as much.

One piece of information that you didn't mention, what temperature is the beer coming out of your tap?
A second piece of information is what temperature is your kegerator set to?

If you have poor air circulation inside your kegerator and the top of your keg and your serving line is warm and the bottom of your keg is cold that will make foamy pours even worse.

The keys to keeping carbonation in your beer are:
  • Keep it cold (38-42 degrees is my preferred range).
  • Keep your keg pressurized to the appropriate serving pressure based on the temperature you set. https://www.kegoutlet.com/media/uploads_ckeditor/Carbonatin-Chart.jpg this carbonation chart helps you determine the correct serving pressure for your keg pressure.
  • Use approximately 1 foot of 3/16" ID beverage tubing per 1 PSI of carbonation pressure. So 10' should get you pretty close
  • Make sure you're pouring into clean glassware

As for your oxidation question, there are a million ways that oxygen can get into your beer, but purging liquid out of your keg with CO2 is a great step at reducing oxidation. But if you are fermenting in a bucket and take the lid off to transfer then you are introducing oxygen. The goal should be to never ever let your beer contact air (at all) after fermentation begins. And that's very difficult to achieve.
Hello, and thanks so much for your responses!

Hmmm...I didn't even realize that there could be different temperatures in the keg while it's sitting in the fridge. The fridge maintains around 38 degrees...of course, when I open the door that 38 degrees goes out the door (literally and figuratively). And, I've never taken the temperature of the beer coming out of the line. I will do that. Being it's a mini-fridge, there isn't a lot of headspace and it's sitting on the bottom of the little fridge, so this all makes sense now.

I am fermenting in a bucket. I have a cast iron bathtub that I fill with water and that's how I'm able to control fermenting temps (and rather accurately I must say) and a bucket provides stability while it's sitting in the tub surrounded by 40 gallons of water. And, my LHBS has regaled me with enough stories about clogged/stuck beer lines from not racking to a secondary that I did transfer to a secondary for my first time kegging. This time, I'm not transferring to a secondary and will see how that goes.

Ok, I'll pick up 12' of beer line and see how that goes.

Again, thanks so much for the info!

P.
 

IslandLizard

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I'd recommend switching over to 4mm ID EVA barrier tubing if you can. It pours great on only 5-6 feet.
That! ^

Use the same line for your CO2 supply too.
You'll also need the special push-to-connect fittings.
Vinyl's out, Eva Barrier's in. ;)

Are you using a picnic tap?
 
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Berube05734

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That! ^

Use the same line for your CO2 supply too.
You'll also need the special push-to-connect fittings.
Vinyl's out, Eva Barrier's in. ;)

Are you using a picnic tap?
Hi, I do have the double walled beer line. I'll see if a longer line will do the trick. And, yes, I'm using a picnic tap and wonder if that cheap thing is contributing to the issue.

Being someone who has never worked in a 'shop' and relatively new to brewing and absolutely new to kegging, the advice is appreciated.
 

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Specifically, which beer line do you have? If it's oxygen-permeable, this may be your remaining oxidation problem, and new line is cheap.

Note that if you make your beer lines too long, you'll still solve your over-foaming problem and the only downside will be a slow pour.

The "shop" comment seems to have been in response to "My LHBS cut me 4' and said I'd be fine." I agree: completely wrong advice from your LHBS. You, on the other hand, seem to be approaching things exactly the right way.

(Oh, and I disagree that your CO2 line has to be oxygen-impermeable. But I've beaten that drum before.)
 
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Berube05734

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Good Morning,

I'm using the: "EVABarrier Double Wall Draft Tubing - 4 mm ID x 8 mm OD" and it pours wicked fast. I opted for this beer line because it stated in the description that it was 'perfect' for when short lines were needed. And, the outer thickness made sense and it was BPA free...

I tried slowing down the rate by partially depressing the picnic tap and that does seem to reduce the level of foam, but doesn't improve carbonation. In desperation and frustration, I tried dispensing holding the glass/tap over my head in an attempt to reduce the flow rate. lol

Am picking up 12' of hose today.

Re oxidation towards the end - I'm sure that was me transferring to a secondary to lessen the chance of too much sediment in the keg causing a blockage. No matter how 'closed' I tried to be in the transfers (secondary and keg), there was obviously introduction to oxygen. I just need practice to become fluid in getting the beer into the keg with little to no oxygen.

It's a learning process and even my mistakes/oversights are pretty tasty. :)

Thx,
P.
 

AlexKay

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That is the right tubing! I take it back: your LHBS wasn't being too irresponsible recommending 4 ft., but it sounds like you'll be happy with more.
 

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@Berube05734 have you thought about the viscosity of the beer you are trying to carbonate? As you mentioned, mile-high beer foam beer with short-lived carbonation, it seems your beer could use some carapils or flaked wheat or oats to thicken it up. If your Co2 settings and your transfer process seem correct, which it does, it is worth focusing on things like mash temperature and adjuncts that promote head retention and lacing.

On my system, eleven-foot lengths of 5mmx8mm double wall EVABarrier tubing give me excellent pours at 10-12psi for all styles of beer I drink.
 
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balrog

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Partially squeezing the picnic tap is a great way to produce turbulence during the pour, which is the opposite of what you want as it will "knock out" CO2 during the pour. Fully open, fully closed, that's the ideal. Lengthen the tubing, calculators are all around (I like this one), to "balance" the system pressure vs pour time for given temp and line length.
 

IslandLizard

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I set the CO pressure to 40 and let it sit for a couple of days and then backed it down to 12.5 and let it sit for a week. Right up to the last glass, I continued to get 4" of foam and flat beer after the first couple of sips.
What is the actual pressure in your keg now?

Burst carbing under high(er) pressure can be tricky, as temp, time, and agitation play a large role in the outcome. I do it, and with great success.
First, the beer is ice cold from crashing after fermentation has completed. Roll the keg for 5-10 minutes under 35-40 psi, until I can't hear the gas streaming in anymore. I then leave it under 12-15 psi, for immediate consumption. I get a somewhat foamy pours and not quite complete carbonation the first few days, improving every day. After 4 days, it's close to perfect, small bubbles, dense foam, just the right amount. I really can't wait 3 weeks for set and forget, although for many beers that may well be the best strategy. I just like em fresher, specially IPAs and other hoppy beers.

How is your picnic tap connected to your 4mm ID EVA line? Are they special picnic taps, perhaps?
All plastic picnic taps I've seen have a barb at the end, good for (stretchy) 3/16" ID thick-walled vinyl line.
 

doug293cz

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Oh, and I disagree that your CO2 line has to be oxygen-impermeable. But I've beaten that drum before.)
If you understood partial pressure, and diffusion science, I'm sure you'd feel differently. The pressurized CO2 inside a gas line has no effect on the O2 diffusing thru the tube wall. The net diffusion rate depends on the O2 partial pressure inside the line (almost 0), the O2 partial pressure outside the line (~3.1 psi), the tube wall thickness, and the diffusion coefficient for O2 thru the tubing material. Gas lines need to be O2 diffusion resistant for the same reason that beer lines need to be O2 diffusion resistant.

Brew on :mug:
 

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If you understood partial pressure, and diffusion science, I'm sure you'd feel differently. The pressurized CO2 inside a gas line has no effect on the O2 diffusing thru the tube wall. The net diffusion rate depends on the O2 partial pressure inside the line (almost 0), the O2 partial pressure outside the line (~3.1 psi), the tube wall thickness, and the diffusion coefficient for O2 thru the tubing material. Gas lines need to be O2 diffusion resistant for the same reason that beer lines need to be O2 diffusion resistant.

Brew on :mug:
My understanding is that diffusion through plastic occurs as solvation of the gases, followed by transport. (If it’s instead transport through nanopores, the situation gets even more complicated.) I don’t see any reason to think that O2 and CO2 will be ideal solutes — that is, their activity may be concentration-dependent. And I think it’s possibly relevant that the system is not at equilibrium, given a constant flow of the CO2 out through the tubing walls.

I did a dive on the academic literature and transport of gases through polymers is an area of active research. I don’t think there’s a clear answer to the question “does O2 diffusion depend on the overpressure of CO2?” If you’re able to point me in the direction of a paper that speaks to this, that would be great. But if your argument is “BECAUSE IDEAL GAXXORS,” I don’t think that’s going to cut it. But brew on!
 

AlexKay

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I’ll add that I have two keezers, one with barrier tubing on the gas line, and one with PVC, and there’s no obvious difference in staling rates. Anecdotal, n=1, etc.
 

doug293cz

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My understanding is that diffusion through plastic occurs as solvation of the gases, followed by transport. (If it’s instead transport through nanopores, the situation gets even more complicated.) I don’t see any reason to think that O2 and CO2 will be ideal solutes — that is, their activity may be concentration-dependent. And I think it’s possibly relevant that the system is not at equilibrium, given a constant flow of the CO2 out through the tubing walls.

I did a dive on the academic literature and transport of gases through polymers is an area of active research. I don’t think there’s a clear answer to the question “does O2 diffusion depend on the overpressure of CO2?” If you’re able to point me in the direction of a paper that speaks to this, that would be great. But if your argument is “BECAUSE IDEAL GAXXORS,” I don’t think that’s going to cut it. But brew on!
Since we are talking about low gas permeability tubing, I think we can safely assume that nano-pores are not a consideration. Deviations from ideality mean the actual behavior is no longer linear, as is the case for the ideal models. But, the deviations from linearity do not fundamentally change what is happening, although any calculations may be somewhat inaccurate. In order for the internal CO2 pressure, and subsequent diffusion out of the tubing, to significantly affect the diffusion of O2 into the tubing, you would have to have some phenomenon where the CO2 diffusing in one direction thru the tubing wall (at least partially) blocks the O2 diffusing in the opposite direction. Have you seen any references to such an effect? It is not necessary to have a detailed knowledge of the mechanics of transport in order to characterize the empirical observations, so no need to get bogged down in mechanistic discussions.

Brew on :mug:
 

AlexKay

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Since we are talking about low gas permeability tubing, I think we can safely assume that nano-pores are not a consideration. Deviations from ideality mean the actual behavior is no longer linear, as is the case for the ideal models. But, the deviations from linearity do not fundamentally change what is happening, although any calculations may be somewhat inaccurate. In order for the internal CO2 pressure, and subsequent diffusion out of the tubing, to significantly affect the diffusion of O2 into the tubing, you would have to have some phenomenon where the CO2 diffusing in one direction thru the tubing wall (at least partially) blocks the O2 diffusing in the opposite direction. Have you seen any references to such an effect? It is not necessary to have a detailed knowledge of the mechanics of transport in order to characterize the empirical observations, so no need to get bogged down in mechanistic discussions.

Brew on :mug:
Yes! We’re on the same page. I think it’s entirely plausible that there are a limited number of solvation sites in the plastic, and that CO2 could occupy these sites, denying them to oxygen. (This would certainly count as a manifestation of non-ideality.) I don’t have a reference, but I contend this is not an “extraordinary claims” situation: non-Fickian behavior, especially in a weird environment like permeable polymer tubing, is more likely than not. (One of the first hits for “non-Fickian diffusion,” when you Google it, is a presentation on mortadella ham, btw.)

So. I don’t think this is an “if you understood diffusion science” situation. I question the application of simple equations to this system. I suspect that if you had a definitive answer, it would be the topic of a current research paper.

I’d recommend that people buying new gas-side equipment get fittings compatible with barrier tubing; there isn’t really any reason not to, and the material is easy to work with. On the other hand, I don’t think it’s worth ripping out and “upgrading” your gas system with the idea that it’s going to gain you anything in terms of oxidation. That’s my assessment of where the science is.
 

TheMadKing

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Yes! We’re on the same page. I think it’s entirely plausible that there are a limited number of solvation sites in the plastic, and that CO2 could occupy these sites, denying them to oxygen. (This would certainly count as a manifestation of non-ideality.) I don’t have a reference, but I contend this is not an “extraordinary claims” situation: non-Fickian behavior, especially in a weird environment like permeable polymer tubing, is more likely than not. (One of the first hits for “non-Fickian diffusion,” when you Google it, is a presentation on mortadella ham, btw.)

So. I don’t think this is an “if you understood diffusion science” situation. I question the application of simple equations to this system. I suspect that if you had a definitive answer, it would be the topic of a current research paper.

I’d recommend that people buying new gas-side equipment get fittings compatible with barrier tubing; there isn’t really any reason not to, and the material is easy to work with. On the other hand, I don’t think it’s worth ripping out and “upgrading” your gas system with the idea that it’s going to gain you anything in terms of oxidation. That’s my assessment of where the science is.

So I'm one of those people that ripped out and upgraded my lines to barrier tubing. It cost me less than $50 and I can definitely tell you that from a purely sensory perspective it made a huge difference in the flavor of the first slug of beer coming out of the lines.

When I had standard poly lines, I could detect oxidative off flavors within 1-2 hours of beer sitting in the lines and I woild always pour off the first ounce or two. Now I'm able to go 1-2 days before I can detect any off flavors from the beer sitting in the lines.

If the beer in the poly lines is getting noticeably oxidized in hours, does the science support that this would be able to migrate through the beer in the lines into the keg over weeks and months?
 

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So I'm one of those people that ripped out and upgraded my lines to barrier tubing. It cost me less than $50 and I can definitely tell you that from a purely sensory perspective it made a huge difference in the flavor of the first slug of beer coming out of the lines.

When I had standard poly lines, I could detect oxidative off flavors within 1-2 hours of beer sitting in the lines and I woild always pour off the first ounce or two. Now I'm able to go 1-2 days before I can detect any off flavors from the beer sitting in the lines.

If the beer in the poly lines is getting noticeably oxidized in hours, does the science support that this would be able to migrate through the beer in the lines into the keg over weeks and months?
Those are the beer lines you replaced, or the gas lines, or both? No one will argue (at least I won’t) that gas-impermeable beer lines are essential. The question is whether the gas lines need to be barrier tubing as well. My personal experience (n=1, etc.) is that they don’t, and my assessment is that there isn’t established science saying otherwise.
 
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Berube05734

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That is the right tubing! I take it back: your LHBS wasn't being too irresponsible recommending 4 ft., but it sounds like you'll be happy with more.
Nope, nothing to take back...they cut me 4' of single walled beer line and said I was fine. Before I hooked everything up to start kegging, it dawned on me to do some research into if there were better beer lines, i.e. maker, material, etc. That's when I discovered the double walled line and figured, why not... it couldn't hurt and could possibly make things better. Unfortunately, when I ordered the tubing online (my LHBS is an hour away) I still went with the length the shop said would be ok.

Responding to balrog - thanks for the FYI re partial depressing. I'd wondered about that, but when I fully depressed the tap, it just dispensed the same amount of foam...just at a faster rate.

Responding to IslandLizard - the pressure remained at 12 psi. When I pressurized initially at 40 psi, I did shake the keg up, but, truth be told, I didn't shake aggressively due to the information I read regarding issues if you don't have a keg set up that you can lay down and roll around. I just didn't know how to figure out if I had a keg that I could lay down.

I was pouring a half glass of beer to clear what's being held in the beer lines assuming it'd taste stale, but one day I drank the glass that I had normally been tossing and it didn't taste stale...at least not to me. Possibly that's owed to the double walled tubing.

I might be becoming a lush...I'm so focused on tasting trying to ascertain flavor, carbonation, etc. that before I know it, I'm staring at the bottom of a glass. lol:D

Thanks to all who have responded!

P.
 

TheMadKing

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Those are the beer lines you replaced, or the gas lines, or both? No one will argue (at least I won’t) that gas-impermeable beer lines are essential. The question is whether the gas lines need to be barrier tubing as well. My personal experience (n=1, etc.) is that they don’t, and my assessment is that there isn’t established science saying otherwise.
Ah, yes I only swapped out the beer lines, I'm using the standard thick walled red poly gas tubing still.
 

doug293cz

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Yes! We’re on the same page. I think it’s entirely plausible that there are a limited number of solvation sites in the plastic, and that CO2 could occupy these sites, denying them to oxygen. (This would certainly count as a manifestation of non-ideality.) I don’t have a reference, but I contend this is not an “extraordinary claims” situation: non-Fickian behavior, especially in a weird environment like permeable polymer tubing, is more likely than not. (One of the first hits for “non-Fickian diffusion,” when you Google it, is a presentation on mortadella ham, btw.)

So. I don’t think this is an “if you understood diffusion science” situation. I question the application of simple equations to this system. I suspect that if you had a definitive answer, it would be the topic of a current research paper.

I’d recommend that people buying new gas-side equipment get fittings compatible with barrier tubing; there isn’t really any reason not to, and the material is easy to work with. On the other hand, I don’t think it’s worth ripping out and “upgrading” your gas system with the idea that it’s going to gain you anything in terms of oxidation. That’s my assessment of where the science is.

So I'm one of those people that ripped out and upgraded my lines to barrier tubing. It cost me less than $50 and I can definitely tell you that from a purely sensory perspective it made a huge difference in the flavor of the first slug of beer coming out of the lines.

When I had standard poly lines, I could detect oxidative off flavors within 1-2 hours of beer sitting in the lines and I woild always pour off the first ounce or two. Now I'm able to go 1-2 days before I can detect any off flavors from the beer sitting in the lines.

If the beer in the poly lines is getting noticeably oxidized in hours, does the science support that this would be able to migrate through the beer in the lines into the keg over weeks and months?
I think you will agree that the chemical potential of the CO2 in the beer is same as the chemical potential of the CO2 in the gas lines. This means that the driving force for CO2 diffusion thru the line walls is the same in both cases. There might be differences in the kinetics of transfer of CO2 into the polymer for the beer and gas cases, but since diffusion thru the polymer is the rate limiting step, the interface kinetics will be a minor effect.

We know that O2 diffusion thru the walls of the beer lines is significant (for highly permeable material), as @TheMadKing 's, and other's, experience shows. Since the CO2 diffusion in the polymer is similar in both cases, any effect of the CO2 diffusion on the O2 diffusion should be pretty much the same. So, O2 must be diffusing into the gas lines, at similar rates as the beer lines, as well.

Brew on :mug:
 

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So I'm one of those people that ripped out and upgraded my lines to barrier tubing. It cost me less than $50 and I can definitely tell you that from a purely sensory perspective it made a huge difference in the flavor of the first slug of beer coming out of the lines.

When I had standard poly lines, I could detect oxidative off flavors within 1-2 hours of beer sitting in the lines and I woild always pour off the first ounce or two. Now I'm able to go 1-2 days before I can detect any off flavors from the beer sitting in the lines.

If the beer in the poly lines is getting noticeably oxidized in hours, does the science support that this would be able to migrate through the beer in the lines into the keg over weeks and months?
My experience was exactly the same. As soon as I noticed the non-oxidized beer coming out of the EVA serving lines, I knew that I had to change over the gas lines as well.
 

Bobby_M

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Those are the beer lines you replaced, or the gas lines, or both? No one will argue (at least I won’t) that gas-impermeable beer lines are essential. The question is whether the gas lines need to be barrier tubing as well. My personal experience (n=1, etc.) is that they don’t, and my assessment is that there isn’t established science saying otherwise.

Here's the thing. The O2 that gets into the beer line is immediately staling 2 ounces of beer and if you pour exactly 2 ounces you taste badly oxidized beer. The O2 that is getting in via the gas lines is likely happening at the same rate, but you won't notice it quickly because it has to oxidize 5 gallons of beer for you to notice. This is a matter of sensory threshold but wouldn't you rather not play chicken with the amount of oxidation you can't detect yet?
 

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Here's the thing. The O2 that gets into the beer line is immediately staling 2 ounces of beer and if you pour exactly 2 ounces you taste badly oxidized beer. The O2 that is getting in via the gas lines is likely happening at the same rate, but you won't notice it quickly because it has to oxidize 5 gallons of beer for you to notice. This is a matter of sensory threshold but wouldn't you rather not play chicken with the amount of oxidation you can't detect yet?
Exactly the point I have been trying to make here.

Brew on :mug:
 

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I think you will agree that the chemical potential of the CO2 in the beer is same as the chemical potential of the CO2 in the gas lines. This means that the driving force for CO2 diffusion thru the line walls is the same in both cases. There might be differences in the kinetics of transfer of CO2 into the polymer for the beer and gas cases, but since diffusion thru the polymer is the rate limiting step, the interface kinetics will be a minor effect.

We know that O2 diffusion thru the walls of the beer lines is significant (for highly permeable material), as @TheMadKing 's, and other's, experience shows. Since the CO2 diffusion in the polymer is similar in both cases, any effect of the CO2 diffusion on the O2 diffusion should be pretty much the same. So, O2 must be diffusing into the gas lines, at similar rates as the beer lines, as well.

Brew on :mug:
It’s an interesting argument. I’m not sure at all that interface kinetics will be a minor effect. We’re not at equilibrium here, and my intuition is that kinetic factors are going to be very important.

Some digging on the internet comes up with the “dual mode sorption” model, which seems to find application (though there are newer approaches) in describing gas diffusion through polymers. There’s a Langmuir-like term, and applications with multiple penetrants absolutely include competition for sites within the material.

I don’t know the answer. Every poster saying “you must use barrier tubing in your gas lines or oxidations, it’s simple diffusion engineering” is appealing to authority, but also doesn’t know the answer. I think it’s good advice to use barrier tubing for gas lines in new installations. I think it’s irresponsible to tell people their beer will improve if they rip out and replace their existing lines.
 

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Here's the thing. The O2 that gets into the beer line is immediately staling 2 ounces of beer and if you pour exactly 2 ounces you taste badly oxidized beer. The O2 that is getting in via the gas lines is likely happening at the same rate, but you won't notice it quickly because it has to oxidize 5 gallons of beer for you to notice. This is a matter of sensory threshold but wouldn't you rather not play chicken with the amount of oxidation you can't detect yet?
“Is likely happening” and “wouldn’t you rather” … sure, maybe, but let’s not say it’s settled science.

The numbers don’t work out, either. If two ounces are severely oxidized in the beer line in a matter of hours, a gallon should be similarly oxidized in weeks. That’s very much counter to my experience.
 

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I suggest setting up a keg of IPA on a 50-foot PVC beer line, and doing some sensory analysis. I can probably get to this in the next month or so if people think it’s the right approach.
 

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I suggest setting up a keg of IPA on a 50-foot PVC beer line, and doing some sensory analysis. I can probably get to this in the next month or so if people think it’s the right approach.
I'd rather see DO data from a properly designed and conducted experiment.

Brew on :mug:
 

AlexKay

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I'd rather see DO data from a properly designed and conducted experiment.

Brew on :mug:
Ultimately, sensory results are what you’re concerned with. With a little critical thinking, one could come up an experiment with a suitable tasting panel and statistical analysis of results. Properly.

But DO is fine, as long as you can agree beforehand on what amount of DO difference would be significant, and have a meter with the appropriate sensitivity.
 

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Ultimately, sensory results are what you’re concerned with. With a little critical thinking, one could come up an experiment with a suitable tasting panel and statistical analysis of results. Properly.

But DO is fine, as long as you can agree beforehand on what amount of DO difference would be significant, and have a meter with the appropriate sensitivity.

Actually I'm more concerned with the raw oxygen data. I think you were suggesting that oxygen may not/probably doesn't get into the beer through the CO2 lines. If I'm mistaken and you actually meant that oxygen does make it into the beer through the CO2 lines but not to a level of sensory detection, correct me.
 

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It’s an interesting argument. I’m not sure at all that interface kinetics will be a minor effect. We’re not at equilibrium here, and my intuition is that kinetic factors are going to be very important.
What matters is if the interface kinetics are anywhere near as slow as the diffusion kinetics. The diffusion kinetics definitely matter, but he diffusion kinetics will be pretty much identical for both lines. If the interface kinetics are more than an order of magnitude faster than the diffusion kinetics (the usual situation), then they won't make a significant difference, even if they are different for the two cases. I need to see some evidence that the interface kinetics are slow enough to matter. Intuition doesn't cut it.

Not being at equilibrium is a red herring. The conditions that matter are very nearly identical for the beer and gas lines, as discussed previously.
Some digging on the internet comes up with the “dual mode sorption” model, which seems to find application (though there are newer approaches) in describing gas diffusion through polymers. There’s a Langmuir-like term, and applications with multiple penetrants absolutely include competition for sites within the material.
Since we have the same gases competing for sites in the two cases, the effects of competition are going to be the same for both cases, so site competition won't drive a different behavior for the two cases.

Brew on :mug:
 

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Ok. Who has a DO meter?
I do, not used it yet though. IMG_20220330_130148.jpg

Only sensitive enough to work out whether my wort is oxygenated enough as it's ppM not ppB.

I like this interpretation of Mike Soltys line calculator as well.


I played around with the final gravity and it doesn't seem to make much of a difference between 1.012 and 1.003, but erring on a little longer but slower is better than waiting on a quick pour full of foam to settle and then it's flat.

Have to say adding in a keg of Saison at 3 vols has been challenging and added to the beer line chaos in the beer fridge.
 

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No, I’m going to stick with the position that transport of CO2 from solution into the polymer is not the same as transport from the gas phase. The relevant timescale to get CO2 from the liquid to the gas or vice versa, as the folks who do set-and-forget carbonation know, is multiple days.

If your intuition is that interface kinetics don’t matter, I’m willing to look at evidence you have on that point.

Anyway, I’m glad we’ve moved on from the proposition that positive pressure of CO2 can’t affect the transport of oxygen through the tubing. (At least I hope we’ve moved on. If we’re still stuck there I can try to provide dual mode sorption references once I’m not typing on my phone.)

Incidentally, I asked a draft system designer I know if the industry worried about O2 coming through gas lines, and got a resounding “nope.” He says red Bevlex 200 (vinyl) is the industry standard. Of course, much more product moves in a commercial application, so this doesn’t necessarily apply for homebrew.
 

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In the absence of evidence/data, we take anti-oxygen measures that are easy and cheap like replacing gas lines. There is some reason to suspect this could be beneficial, even though hard (or any!) data aren't available. And even though the intuitions of educated, articulate, experienced people vary considerably. Fun discussion though. Cheers!
 

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Incidentally, I asked a draft system designer I know if the industry worried about O2 coming through gas lines, and got a resounding “nope.” He says red Bevlex 200 (vinyl) is the industry standard. Of course, much more product moves in a commercial application, so this doesn’t necessarily apply for homebrew.

There are a lot of people bouncing around in their profession that don't really go too much further than "this works fine" for their entire careers. I'm just saying that it's not the final word on the topic by any means. No commercial account that is turning over a half barrel of bud light (another industry standard) in a weekend is going to complain that their customers tasted a bit of oxidation. Half the consumers of such beers have no problem pumping air into a keg on the deck for 8 hours.

I personally hate opaque 5/16 and 3/8" ID bevlex for two reasons. One is that it's unnecessarily oversized for what it's doing. Two, if you get beer backed up into the lines, you'd never know it.
 
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