Stratification of gases in closed environments (Like fermentors and kegs)

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Setesh

Setesh

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I posted an unproven theory of mine in another thread. That theory was that if I filled a new keg with CO2 that the CO2 might settle to the bottom in a few hours and then push more of the O2 out the top when I purged. Another poster made the point that gases mix very quickly and so this theory has no merit. You can find the conversation starting on post 9 here:
https://www.homebrewtalk.com/f35/transporting-kegs-395265/

This conversation got me thinking.

I know gases mix easily in open environments because of currents and convection. Any movement in an environment will facilitate mixing. Is this the case in a closed environment like a keg or fermentor? In a fermentor there are yeast producing CO2 during fermentation and the beer is off-gassing afterwards, so there is bound to be some type of convection going on for quite a while I would think. If that is the case and I displace some of that CO2 with a wine thief then the air that replaces it will mix very quickly with the CO2 in the headspace.

I have always thought of the CO2 in a fermentor or keg as a protective blanket or layer. If any introduced air is quickly mixed with this layer then it isn't a protective blanket at all. I have been browsing the web for a while trying to find research to back up either side of this argument and so far it looks like stratification of gases is pretty difficult to obtain to any meaningful degree unless you have a very tall column of gas (much taller than we are talking about with brewing equipment).

I was hoping to get input from others on this subject and hopefully come to a conclusion one way or another.
 
Here is an interesting document on CO2 stratification in caves.

http://caves.org/pub/journal/PDF/v71/cave-71-01-100.pdf

The author postulates that CO2 is found in low places in caves mainly because that is where it is being created in the first place. It then takes a while to disperse into the environment. Because of this one might think that it had settled, when in actuality it just hasn't had a chance to go somewhere else yet.

I am a diver and I started thinking about air mixes in cylinders. If you make nitrox by mixing in cylinder you are supposed to tumble the cylinder to mix the gases. Once the gases are mixed they are considered stable, although you should always check with a meter before using the cylinder.
This would tend to show that if gases are separate in a closed environment they might not mix quickly or at all on their own, but once they are mixed they will stay mixed. Here is some supporting math and confirmation by a professor of science that gases don't un-mix:

http://www.newton.dep.anl.gov/askasci/chem03/chem03325.htm

So the question becomes how quickly and easily do they mix in the first place? If they mix easily then the CO2 blanket theory is unsound.
 
Setesh said:
http://www.newton.dep.anl.gov/askasci/chem03/chem03325.htm

So the question becomes how quickly and easily do they mix in the first place? If they mix easily then the CO2 blanket theory is unsound.
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I'm NO scientist, so I'll look forward to a real scientist coming and and giving us the proper explanation.

I can give you my anecdotal experience, as well as my thoughts, though!

First, I'm always troubled by this "co2 blanket" theory, as even in an active fermentation the headspace is never 100% c02. It may be mostly co2, and during active fermentation this is not a concern. But after fermentation, this protective c02 blanket will not be there forever.

The way I think of it is this- we inhale air (using the oxygen in it) and exhale c02 (for the most part- again, never 100%). If this "c02 blanket" was as persistent as people seem to think, we'd all die in our sleep from co2 poisoning as the co2 would never rise.

I understand that in a carboy with an airlock, that there would be a significant amount of co2 in the carboy. But since it's never going to be 100% full of co2 (even with purging), that oxidation can occur in the long term. That's why winemakers top up, reducing any headspace, so that the area exposed to air is minimized. They also use antioxidants (sulfites).

If you look at the infections posted on this forum, they are almost always either in a bucket with wide headspace, or in secondary with headspace. Oxygen loving bacteria will take hold in an area with headspace, sooner or later, usually.
 
OK, so gases mix MUCH faster than liquids. This process is called diffusion. Basically particles of gas naturally want to go from areas of higher concentration to areas of lower concentration. This naturally balances the mixture. The rate can be calculated by using Grahams Law:

http://library.thinkquest.org/12596/graham.html

So as far as I can see, there is no such thing as a CO2 'blanket'. I think of a blanket as a cover, something that is not easily passed through. A CO2 layer is present after fermentation, but it is a volatile layer, not a protective blanket. Any air that is introduced into the headspace will mix with the CO2, not lay on top of it.

So thank you very much day_trippr for starting me down this path of education. I love learning new things, and discovering I'm wrong about something is usually the first step in the process :D

I really hope a scientist or other big brained individual can come along and lay this out for us in lay terms because I can't seem to calculate how long diffusion takes. I tracked down the molecular weights of gases here:
http://www.engineeringtoolbox.com/molecular-weight-gas-vapor-d_1156.html
and the calculator here:
http://www.1728.org/graham.htm
But the answer is still meaningless to me. What does a rate of .8 mean? Is that fast or slow? How many seconds/minutes is that?
Anyone?
 
Yooper said:
I'm NO scientist, so I'll look forward to a real scientist coming and and giving us the proper explanation.

I can give you my anecdotal experience, as well as my thoughts, though!

First, I'm always troubled by this "co2 blanket" theory, as even in an active fermentation the headspace is never 100% c02. It may be mostly co2, and during active fermentation this is not a concern. But after fermentation, this protective c02 blanket will not be there forever.

The way I think of it is this- we inhale air (using the oxygen in it) and exhale c02 (for the most part- again, never 100%). If this "c02 blanket" was as persistent as people seem to think, we'd all die in our sleep from co2 poisoning as the co2 would never rise.

I understand that in a carboy with an airlock, that there would be a significant amount of co2 in the carboy. But since it's never going to be 100% full of co2 (even with purging), that oxidation can occur in the long term. That's why winemakers top up, reducing any headspace, so that the area exposed to air is minimized. They also use antioxidants (sulfites).

If you look at the infections posted on this forum, they are almost always either in a bucket with wide headspace, or in secondary with headspace. Oxygen loving bacteria will take hold in an area with headspace, sooner or later, usually.
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I wonder how permeable our rubber bungs and better bottles are? Gases can and will transfer through solids. Here is an excerpt taken from:
http://encyclopedia2.thefreedictionary.com/Gas+Permeability

The gas permeability of substances is defined in terms of the penetrability effect P, expressed in units of m4/(sec·N), or cm2/(sec·atm), where 1 cm2/(sec·atm) = 1.02 x 10-9 m4/(sec·N), and by the volume of gas that passes through a unit area (perpendicular to the gas flow) in the body in 1 sec with a pressure differential of 1. The coefficient P depends on the nature of the gas, and therefore the gas permeability of substances is usually compared on the basis of their hydrogen permeability. The values of P, in cm2/(sec·atm), of several materials at 20° C are presented in Table 1.

Table 1. Values of the penetrability effect (P) (20° C)
Metals ............... 10-18 to 10-12
Glass ............... 10-15 to 10-10
Polymers (films) ............... 10-12 to 10-5
Liquids ............... 10-7 to 10-5
Paper, skin ............... 10-5 to 10

So there will be some intrusion into a plastic fermentor by gasses, especially the lighter ones, through the plastic itself, the rubber bung, and the plastic airlock. Glass is going to block gas transport from what I can tell, and so will metal. So once your beer is in a keg it's all down to what's in the headspace. It seems like a bucket is going to be most permeable, then better bottles, and finally a glass carboy will be least permeable.
 
If you want to see gas stratification, look for pictures of Chlorine gas leaks. Chlorine will pool in low lying areas until enough wind comes along to mix and dispurse it.

As for the breathing thing, you don't inhale 100% O2 and what you do inhale, you don't completely convert to CO2.

This is why mouth-to-mouth works. 20% is normal oxygen in air. 15 - 19% decreases your ability to work. 10 - 12% is about as low as you want to go because your lips will turn blue. Below 10% and you'll pass out. Below 6% is fatal.

(These are among the reasons I won't do confined space entry.)

Gases in a 100% closed environment will eventually become completely mixed. But with out agitation, it occurs slowly through random Brownian motion and the Ideal Gas law.

A fermenter is a partially enclosed environment. Gas can get out but can't get in. Plus you have a source of CO2 gas generation at the wort surface. As CO2 is generated at the surface, it displaces the air closest to the air lock. Therefore, my reasoning is that the headspace of a fermenter is like a plug flow reactor. The CO2 generated by the fermentation will eventually push everything that was in the headspace up and out. There will be some mixing along the interface, but not so much to overcome the gradient of CO2 production during the most active phase of fermentation.

Now remember when you pitched the yeast and then aerated the hell out of the wort? You supersaturated the wort with O2. So some O2 will also come out of the wort as it ferments. But it's a small amount compared to the CO2 being produced.

When you rack a beer to a secondary, even though fermentation has stopped, the beer is supersaturated with CO2. So when you slap the airlock on it and see it bubbling, you are seeing plug flow working again. However, in this situation, there probably isn't enough CO2 coming out of solution to completely displace everything that was in the headspace.
 
Above absolute zero all matter has vibrational energy. This will cause gasses to diffuse into one another(mixing). They will diffuse until the mix is homogeneous throughout. Room temp is considerably warmer than abs. zero, so mixing is assured.
A 'blanket' could develop if CO2 were continuously evolved from the wort, and it helps that the wort is on the bottom of the vessel. It would help if the evolved CO2 were cooler than the headspace.
Instead of invoking complex phys. chem. theory, try these: Introduce CO2 from your cylinder; introduce CO2 from an active batch; Fill headspace with a clean, thin, vented(up) plastic bag. As CO2 is generated, bag is collapsed and you eventually remove it; use N2, as I do, if you have it; use(at your own risk) freon from a can. didn't think of that one, did ya? Do that at your own risk, as I cannot be responsible for, well, whatever.
As for permeability through vessel walls, I think it would occur in both directions, and you would smell at least some of the small molecules from the ferment.
 
Beernik said:
If you want to see gas stratification, look for pictures of Chlorine gas leaks. Chlorine will pool in low lying areas until enough wind comes along to mix and dispurse it.
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Chlorine has a molecular weight of 70 so it's very heavy, I assume that is why it settles so easily and is so hard to displace?

Those pictures remind me of dry ice fog on halloween
 
N2 is ~ 28
O2 is ~ 32
CO2 is ~ 44
Cl2 is ~ 71

Chlorine gas leaks are one of those things that make my butt pucker. I've met guys that have been exposed. It's the safety aspect that has driven water suppliers to go to the chloroamines we hate so much in our brew water.
 
Beernik said:
Now remember when you pitched the yeast and then aerated the hell out of the wort? You supersaturated the wort with O2. So some O2 will also come out of the wort as it ferments. But it's a small amount compared to the CO2 being produced.
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I understood that yeast will consume all of the oxygen in suspension: http://www.wyeastlab.com/comm_b_oxygenation.cfm

Interesting thread. I wonder if gasses of similar weights mix more than those of differing weights, or ultimately (like a container with washed yeast) will they all separate into layers.

I know you don't want to have Carbon monoxide in an unventilated basement, for an example similar to the cited Chlorine Gas one.
 
5th paragraph:

Some yeast strains have higher oxygen requirements than others. It is generally safe to assume that you need at least 10ppm of oxygen. 10ppm will supply adequate oxygen in most situations. Over-oxygenation is generally not a concern as the yeast will use all available oxygen within 3 to 9 hours of pitching and oxygen will come out of solution during that time as well. Under-oxygenation is a much bigger concern.
 
Cyclman said:
I understood that yeast will consume all of the oxygen in suspension: http://www.wyeastlab.com/comm_b_oxygenation.cfm

Interesting thread. I wonder if gasses of similar weights mix more than those of differing weights, or ultimately (like a container with washed yeast) will they all separate into layers.

I know you don't want to have Carbon monoxide in an unventilated basement, for an example similar to the cited Chlorine Gas one.
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Carbon Monoxide binds to hemoglobin in your red blood cells easily out competing oxygen thus suffocating you with nothing more than a chemical reaction. No odor to detect and the symptoms can last for weeks (if you're alive)

Chlorine gas causes lung edema.... basically your little alveoli (lung sacks where gas exchange takes place) to fill with fluid thus preventing oxygen to the bloodstream and creating hypoxia. Chlorine is a halogen and quite reactive with water and biological material. Stupid electrons!

Very different processes. OP, what exactly are you asking?
 
Here's another question:

If your beer is already saturated with CO2 does that change it's ability to absorb oxygen? During fermentation it has become as saturated as it can be at atmospheric pressure with CO2, and off gassed the rest. Does this make it less likely to absorb O2?
 
Setesh said:
Here's another question:

If your beer is already saturated with CO2 does that change it's ability to absorb oxygen? During fermentation it has become as saturated as it can be at atmospheric pressure with CO2, and off gassed the rest. Does this make it less likely to absorb O2?
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Interestingly, winemakers and meadmakers often degas the wine during primary. Not so much to introduce oxygen, but instead to get rid of the c02 (which is poisonous to yeast).

One of the reasons keggers purge the keg with co2 is to protect it from oxidation risks. It's not because it binds with the beer, but as it's heavier than oxygen- which takes us back to the original question of the "c02 blanket" in the first place! :p
 
Beernik said:
5th paragraph:

Some yeast strains have higher oxygen requirements than others. It is generally safe to assume that you need at least 10ppm of oxygen. 10ppm will supply adequate oxygen in most situations. Over-oxygenation is generally not a concern as the yeast will use all available oxygen within 3 to 9 hours of pitching and oxygen will come out of solution during that time as well. Under-oxygenation is a much bigger concern.
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I'm a little more wary of over-oxygenation than this. While I agree that under-oxygenation is a concern, I suggest that you don't want to go overboard with oxygenation. Jamil Z has mentioned that he has anecdotal evidence that higher alcohols and solventy notes can be produced when the wort is over-oxygenated. I also have limited evidence to that effect. So don't go super-oxygenating wort...get the right amount in there.
 
mabrungard said:
I'm a little more wary of over-oxygenation than this. While I agree that under-oxygenation is a concern, I suggest that you don't want to go overboard with oxygenation. Jamil Z has mentioned that he has anecdotal evidence that higher alcohols and solventy notes can be produced when the wort is over-oxygenated. I also have limited evidence to that effect. So don't go super-oxygenating wort...get the right amount in there.
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I have heard repeated that "8 ppm" is a good goal. Is that your experience? Or is the "at least 10 ppm" quoted above a better bet?
 
Yooper said:
I have heard repeated that "8 ppm" is a good goal. Is that your experience? Or is the "at least 10 ppm" quoted above a better bet?
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To complicate matters, how do you know you have 10ppm and not 9 or 16? If 8ppm is the best you can do with air, then you know you haven't gone over that by shaking, air stone, whatever. But If I give 30 seconds of pure O2 through a diffusion stone I don't have any way of knowing how many ppm I've just introduced. According to Wyeast you can get up to 26ppm using pure O2 and a stone, but 60 seconds should be 12ppm. I assume the actual amount depends on the SG of the wort and the distance the bubbles travel through it. Without a meter I don't see any way of knowing the end result. I've always done 60 seconds of pure O2 through a .5 micron stone and had good results, but I don't have any way of knowing if that equals 12ppm or not. Since different yeast strains have different oxygen needs, I should probably adjust my times accordingly. But since I don't know what ppm I'm ending up with I don't have any baseline to adjust from.

http://www.wyeastlab.com/hb_oxygenation.cfm
 
The short answer to your initial question is that gases of similar densities won't stratify very much at all, and certainly not quickly. In addition, if you're purging a vessel under pressure, letting out the gas will be rather violent and cause mixing of the gases in the vessel.

Depending on the situation, though, gas doesn't always mix quickly. CO2 certainly will produce layers. You can get CO2 buildup in the bottoms of valleys if something is producing enough of it. I personally saw this a lot with nitrogen gas from liquid nitrogen. Cold nitrogen gas is pretty dense, and it can quickly fill an enclosed room from the bottom up. It then takes quite a while for the N2 to diffuse out through the door unless you turn on some fans.

When your fermenter is closed, of course, the CO2 stays put because the vessel is airtight*. Whenever you open it, some of it will mix with the nearby air. The more you mess with it (e.g., using a wine thief), the more mixing. But you can mostly preserve that layer if the container is only open briefly. Certainly we did that a lot with vacuum chambers: it would be purged with dry N2, then we'd open it up and do some work inside, and when we closed it up it would still be mostly dry N2. Note that the aperture of your vessel will play a big role here, so a carboy is going to preserve its CO2 much better than a bucket.

* It's not actually airtight. But it's probably pretty close. That's ignoring the airlock, which is like a one-way valve during fermentation. Which makes me wonder -- why don't they sell airlocks with actual one-way valves to prevent suckback?
 
Yooper said:
I
One of the reasons keggers purge the keg with co2 is to protect it from oxidation risks. It's not because it binds with the beer, but as it's heavier than oxygen- which takes us back to the original question of the "c02 blanket" in the first place! :p
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Isn't the situation with a keg a bit different in that it is a closed environment and under pressure? You should be able to get most of the O2 out of a keg by purging correct?
 
The problem is complicated enough that prediction of what will happen in an individual case is difficult (or beyond me at any rate) but we can look at the physics a bit to try to gain insight. If we have two ideal gasses, one of which has a lower molecular weight than the other at the same pressure and temperature the higher molecular weight gas will be denser. Lets say it is in the bottom half of a container and separated from the less dense half by a magical partition which can be withdrawn without disturbing the gasses. We withdraw it and ask whether the gasses will mix or if the layers will remain. Absent gravity there will be chemical potential gradient across the boundary and each gas will flow along that gradient until the gradient doesn't exist any more which happens when the two gasses are completely mixed i.e. any molecule of either gas is equally likely to be anywhere in the container.

In a gravitational field there is an additional potential to consider and that is the gravitational one. The chemical potential is offset to some extent by the gravitational potential. Chemical potential wants to force the heavy gas molecules up into the lighter gas space but the gravitational potential wants to hold them back. Chemical potential wants to force light gas molecules down into the heavy gas space and gravitational potential does too but the gravitational potential is less for the lighter gas. Thus it seems that a layer would form or rather that the probability of finding the heavier gas molecules in the bottom of the container is larger as both types of molecules are whizzing about as they are at finite temperature.

In fact, of course, layers do form, at least temporarily as anyone who has seen CO2 poured into a glass with a candle in it in grammar school science class knows. Also in weather systems, even with winds for mixing, cool air masses slip under warm air masses and these conditions can persist for hours or even days.
 
[QUOTE why don't they sell airlocks with actual one-way valves to prevent suckback?[/QUOTE]

I have been thinking about picking up some of these for my better bottles:

http://www.midwestsupplies.com/better-bottle-drytrap-airlock.html

Every time I pick one up I always get suckback. I use vodka in my airlocks because of this, so I'm not too worried about the liquid, but the air that comes with it.
 
ajdelange said:
The problem is complicated enough that prediction of what will happen in an individual case is difficult (or beyond me at any rate) but we can look at the physics a bit to try to gain insight. If we have two ideal gasses, one of which has a lower molecular weight than the other at the same pressure and temperature the higher molecular weight gas will be denser. Lets say it is in the bottom half of a container and separated from the less dense half by a magical partition which can be withdrawn without disturbing the gasses. We withdraw it and ask whether the gasses will mix or if the layers will remain. Absent gravity there will be chemical potential gradient across the boundary and each gas will flow along that gradient until the gradient doesn't exist any more which happens when the two gasses are completely mixed i.e. any molecule of either gas is equally likely to be anywhere in the container.

In a gravitational field there is an additional potential to consider and that is the gravitational one. The chemical potential is offset to some extent by the gravitational potential. Chemical potential wants to force the heavy gas molecules up into the lighter gas space but the gravitational potential wants to hold them back. Chemical potential wants to force light gas molecules down into the heavy gas space and gravitational potential does too but the gravitational potential is less for the lighter gas. Thus it seems that a layer would form or rather that the probability of finding the heavier gas molecules in the bottom of the container is larger as both types of molecules are whizzing about as they are at finite temperature.

In fact, of course, layers do form, at least temporarily as anyone who has seen CO2 poured into a glass with a candle in it in grammar school science class knows. Also in weather systems, even with winds for mixing, cool air masses slip under warm air masses and these conditions can persist for hours or even days.
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It's ridiculously complicated. It makes me think of chaos theory, the whole "a butterfly flaps its wings in Peeking and it rains in New York City" thing. So many tiny factors can have huge effects on the system. I love stuff like this, I just wish I had the equipment and training to do some testing.
 
smakudwn said:
Isn't the situation with a keg a bit different in that it is a closed environment and under pressure? You should be able to get most of the O2 out of a keg by purging correct?
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Closed environment is very different. You could purge a keg with a lighter-than-air gas, too. (Okay, you couldn't purge it, open it up, pour in beer, and expect much gas to be left. But after filling, you could purge a keg with helium, for example.)
 
Setesh said:
I have been thinking about picking up some of these for my better bottles:

http://www.midwestsupplies.com/better-bottle-drytrap-airlock.html

Every time I pick one up I always get suckback. I use vodka in my airlocks because of this, so I'm not too worried about the liquid, but the air that comes with it.
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$16 seems like a lot for a check valve.

You get suckback when you pick up a better bottle? Does it flex or something (blow out air when you grab it, suck back when you let go)? Might want to consider switching your airlock for a solid stopper during those times.
 
It's interesting to think a bit about purging air from a closed keg with another gas. Assuming you have a keg at 15 psia (1 atm but let's call it 15 instead of 14.7 to make the math a little easier) and pressurize it to 30 psig (45 psia) with another gas. You now bleed back to 15 psia having expelled 2/3 of the mixed gasses (the other gas shooting into the keg is going to result in pretty good mixing even if it is much heavier than the air in the keg) and thus 2/3 of the air. The keg now contains 1/3 of the original air and the rest is the purging gas. Repeat and you have 1/3 of 1/3 of the original air and so on. Thus after 3 purgings you will still have 1/27th (3.7%) of the original air and after four, 1.2%. Given the destructiveness of air (oxygen) to beer which is to be stored for any length of time it is clear that this isn't a very good way to purge a keg of air. A more effective means is to fill the keg completely full with water (which has been boiled to kill anything in it) and then push that out with CO2. Another method (the one I use) is to sterilize the keg (Sankey - don't see how you'd do this with Cornies) with steam and connect CO2 as soon as the steam is disconnected so that the steam's volume is replaced by CO2 as the steam condenses.
 
ajdelange said:
Thus after 3 purgings you will still have 1/27th (3.7%) of the original air and after four, 1.2%. Given the destructiveness of air (oxygen) to beer which is to be stored for any length of time it is clear that this isn't a very good way to purge a keg of air. A more effective means is to fill the keg completely full with water (which has been boiled to kill anything in it) and then push that out with CO2.
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So what I do and tell myself is accomplishing something better is to run the CO2 in through the liquid out line, while venting the whole time through the PSV, which I convince myself means I'm expelling out the air as I fill with CO2 from the bottom. In reality, there's probably enough mixing that I'm deluding myself. :p

Since I'm not particularly interested in boiling 5 gallons of water every time i want to evacuate a keg, I'm wondering if putting some star-san in the keg, and then running CO2 through it would work. Thought being that if the starsan foamed enough to fill the keg with CO2 bubbles, that would successfully exclude the O2.
 
Don't know how the bubbles would work but filling the keg with water that has been treated with a no rinse sanitizer obviously would if you could get all that water out (remove the last bit through the pressure relief valve perhaps). If the keg has already been sanitized then you could use the minimum dose of sanitizer as you can let it sit in the keg for a good long time. Clearly you would want to 'daisy chain' several kegs if you do this. Too much trouble for just 1 keg.
 
Re: airlocks and suckback - I use these guys http://www.usplastic.com/catalog/item.aspx?itemid=36843 instead of airlocks when I'm not using blowoff tubing. They are under a buck and fit nice and snug into the drilled stopper. Pump some sanitizer through it to "crack" the valve as they take a bit of pressure to open up when they're brand new. They're also a lot easier to remove than those cheap airlocks - I can never seem to get one of those out of the stopper without breaking it.

I think the primary benefit of the DryTap is that the o-ring closure it mates with is supposed to have lower oxygen permeability than a rubber stopper or a carboy cap. Better Bottle has a study somewhere on their website which lists the oxygen permability of all common fermenting vessels, closures and airlocks. IIRC, carboy caps fare extremely poorly as do airlocks.
 
ajdelange said:
Don't know how the bubbles would work but filling the keg with water that has been treated with a no rinse sanitizer obviously would if you could get all that water out (remove the last bit through the pressure relief valve perhaps). If the keg has already been sanitized then you could use the minimum dose of sanitizer as you can let it sit in the keg for a good long time. Clearly you would want to 'daisy chain' several kegs if you do this. Too much trouble for just 1 keg.
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I bet that would work. Fill entire keg with starsan, to the very brim, put the lid on, attach a line and purge entire keg with CO2. Flip it over and purge out the relief valve to get rid of the last couple of ounces of sanitizer, then fill with beer through the out post.
 
judsonp said:
$16 seems like a lot for a check valve.

You get suckback when you pick up a better bottle? Does it flex or something (blow out air when you grab it, suck back when you let go)? Might want to consider switching your airlock for a solid stopper during those times.
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I have tried that, but it just turned my Better Bottle into a pop gun. I really like the light weight of them, and they fit perfectly in my mini fridge fermentors, but I hate the flexibility and scratchability.
 
ajdelange said:
A more effective means is to fill the keg completely full with water (which has been boiled to kill anything in it) and then push that out with CO2.
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ajdelange said:
Clearly you would want to 'daisy chain' several kegs if you do this. Too much trouble for just 1 keg.
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I think this sounds like a workable idea, but you would need a lot of fittings to make 'bridges' out of.
Boil 6 gallons of water, fill up corny keg 1 to the rim, put on lid, attach CO2 line, attach beer out line on keg 1 to gas in line on keg2, and daisy chain them all the way down the line. You leave the purge valve open on the last keg and pump the water through all of them to the end. Because of the dead space at the bottom of each keg you would end up with water loss of a couple of ounces on each keg though. I don't see a way around that unless you did it one keg at a time. You then fill them via the beer in line and you have no O2 exposure.
 
You want every mL of air pushed out so you would want to fill completely through the liquid line with the gas connector off then open the pressure release valve and push more liquid until it is coming out the pressure release. Then connect the next keg in series and continue for that one and so on. Yes, you would have to make up some 'jumper' lines.

Leave some CO2 pressure on each keg (you will want to do that anyway for counter pressure filling), disconnect the lines. Depress the poppets briefly so any liquid left in the filler or gas tubes gets blow out. Now invert the kegs so that the remianing liquid in them runs down onto the lid and then open the PRV lever briefly. This will blow the last of that liquid out. I wouldn'r want a couple of hundred mL of even no rinse sanitizer left in the keg to mix with my beer.

It's been so long since I used Cornies that I can't remember how I used to do it. If you purge with CO2 3 times to get air down to 1/27 of a kegfull (that's 700 mL of air with 140 mL of O2 in it) and then fill with beer until it comes out the gas line and PRV you will have pushed out all the air and while you have exposed the beer to that 140 mL of oxygen during the filling process that is 27 times better than the exposure it would have had if you filled the keg w/o having purged first.
 
ajdelange said:
It's been so long since I used Cornies that I can't remember how I used to do it. If you purge with CO2 3 times to get air down to 1/27 of a kegfull (that's 700 mL of air with 140 mL of O2 in it) and then fill with beer until it comes out the gas line and PRV you will have pushed out all the air and while you have exposed the beer to that 140 mL of oxygen during the filling process that is 27 times better than the exposure it would have had if you filled the keg w/o having purged first.
Click to expand...

And for me, that's been good enough for all of my kegs.

I purge, keg, purge, and set it in the kegerator. Normally, the beer is gone in a couple of weeks, but not ever more than a month. Since oxidation flavors worsen with time, this really hasn't been an issue with me at all.

Of course, I drink my beer pretty quickly. If I'm not drinking it quickly, then I will bottle (via my beergun) it but that's only happened a couple of times in the last few years.
 
Setesh said:
I think this sounds like a workable idea. . .
Click to expand...
Workable, sure. Sane, not even close. Say you have less than two inches of head space in your keg and 1.2% of that is ambient air after purging. Only 21% of the 1.2% is even oxygen. As the keg is served the percentage becomes even less. And given the original volume in the head space this all seem a bit OCD even for me. :cross:
 
Quite sane, actually. Some of the best brewers I know use such techniques and are able to enjoy their beers for a year or more. These are guys that brew lots and lots of beer and want to make comparisons over a period of time as they research modifications to their processes for a particular style for example (I'm thinking of Gordon Strong here). If you brew a batch and knock it back within a few weeks then it's not necessary to do any of this. You can just siphon from the carboy into an open Corny and put the lid on but if you are a serious brewer your beer is never touched by air from the time you seal the fermenter at pitching until the time it hits your glass. You clearly do not understand how sensitive beer is to O2.
 
You guys need to stop adding so much O2 to your kegs. I store mine with air, which is mostly N2. Its only about 20% O2. Also the solubility of co2 is much greater than O2. You could spend a little time with hernys law and figure out the precise amount of o2 would enter your beer at what pressure. I would do it for you but I stopped doing other peoples homework a long time ago.
 
It has little to do with Henry's law. It is well known in the industry that even minute amounts of oxygen in the headspace of a beer package will result in the staling of beer that is to be kept for even relatively short periods of time. One of the reasons the bottling machine is the most expensive piece of equipment in the brewery is because of the great difficulty in keeping 'airs' down. Savvy home brewers learn from what the commercial guys already know. They regard oxygen with about the same level of esteem they grant pediococcus.
 
ajdelange said:
Quite sane, actually. Some of the best brewers I know use such techniques and are able to enjoy their beers for a year or more. These are guys that brew lots and lots of beer and want to make comparisons over a period of time as they research modifications to their processes for a particular style for example (I'm thinking of Gordon Strong here). If you brew a batch and knock it back within a few weeks then it's not necessary to do any of this. You can just siphon from the carboy into an open Corny and put the lid on but if you are a serious brewer your beer is never touched by air from the time you seal the fermenter at pitching until the time it hits your glass. You clearly do not understand how sensitive beer is to O2.
Click to expand...

That's what I was thinking it would be useful for. Something that is going to be around a very long time. A Hefe I wouldn't bother, but a Barleywine I think could benefit. Is it anal? maybe. Does that bother me? Not in the least!
 
Not to take away from the fighting, but does O2 have to dissolve to cause damage? Can't it oxidize the surface layer of the beer without dissolving into solution? That's how oxidization occurs on solids like metals, right?
 

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