Keg conditioning-I'm missing something

[beerluvva]

This weekend I'm trying to tap a 3 gal corny keg of a brew that spent 2 weeks in primary, then was racked to the keg with 6 Tbsp corn sugar simple syrup. It has been in keg for 2 weeks at 72F. The day it was kegged I charged it with a cylinder of co2, bled it, and recharged to evacuate oxygen.

I tapped today... Two things: 1. Tons of foam, 2. Very little carbonation.

I have put the keg into my fridge, in hopes that they reduced temp will help the beer absorb some more co2. There appears to be plenty of co2 pressure on the keg.

Any recommendations ? I plan on trying the keg again after 24 hrs.

Thanks !
Beerluvva

 

[mattd2]

Wait till it cools down. Any keg natural/forced carb will foam like hell if tapped at room temperature ( and it is also likely the pressure was higher in the keg at room temp)
Once it is cooled down, bled down the pressure to your normal serving pressure.

 

[n240sxguy]

Just out of curiosity, if you have a keg, why would you not force carbonate? I haven't naturally carbed anything since I got my keg setup.

 

[BigFloyd]

Lots of foam and very little carbonation is exactly what any of us would get trying to dispense at room temp.

Give this one at least 3 days after it cools down into the 38-39*F range.

 

[beerluvva]

Just out of curiosity, if you have a keg, why would you not force carbonate? I haven't naturally carbed anything since I got my keg setup.

Well, I got into kegging as a way to avoid bottling. So, batch priming and natural carbonation is what I know. Also, I tend to favor processes that minimize equipment and overhead, so I've avoided the force carbing tank, regulator, kegerator, etc. But having said this, force carbing does seem attractive....

From the previous posts, it seems my mistake is trying to dispense at room temp.

I think I'm getting confused by the idea of "cask conditioned" ales, which I though were to be served at room temp. I also understand cask conditioned ales will have lesser carbonation, but this keg is all but flat as I tried it.

So to recap, it seems like what I could do in the future is:
1. carb (batch primed keg) at room (basement) temp ~ 70 F
2. 3 days prior to serving, chill the keg in fridge
3. if more carb is desired, serve cold...for less carb, the "cask conditioned ale" thing, allow keg to warm somewhat, but not all the way back to room temp
or
4. the hell with all this, and force carb
is this right ?

thanks again, all, very helpful as always!

 

[BigFloyd]

Well, I got into kegging as a way to avoid bottling. So, batch priming and natural carbonation is what I know. Also, I tend to favor processes that minimize equipment and overhead, so I've avoided the force carbing tank, regulator, kegerator, etc. But having said this, force carbing does seem attractive....

From the previous posts, it seems my mistake is trying to dispense at room temp.

I think I'm getting confused by the idea of "cask conditioned" ales, which I though were to be served at room temp. I also understand cask conditioned ales will have lesser carbonation, but this keg is all but flat as I tried it.

So to recap, it seems like what I could do in the future is:
1. carb (batch primed keg) at room (basement) temp ~ 70 F
2. 3 days prior to serving, chill the keg in fridge
3. if more carb is desired, serve cold...for less carb, the "cask conditioned ale" thing, allow keg to warm somewhat, but not all the way back to room temp
or
4. the hell with all this, and force carb
is this right ?

thanks again, all, very helpful as always!

At this point, I must admit some confusion. How is it that you are pushing your beer out of the tap?

Even folks that sugar/yeast carb in the keg still have a service system that involves CO2, even if it's one of the little 12g cartridges.

 

[beerluvva]

Hi

I do have the co2 cartridges, which I use to purge /seal the kegs, and I can use as well for dispensing.

However, because I don't know what I'm doing, for this keg and the few I've done before, i've found that there is so much pressure in the room temp keg, the beer comes flying out, but super foamy.

With your advice on chilling for 3 days, I'm inferring that a lot of the co2 will get absorbed into the beer, and then I'd need to use a cartridge for serving?

 

[BigFloyd]

Hi

With your advice on chilling for 3 days, I'm inferring that a lot of the co2 will get absorbed into the beer, and then I'd need to use a cartridge for serving?

Yes. And use it sparingly until you see what's needed to push the beer since I'm assuming that you're using a picnic tap and a short (3ft or so) line.

It's kind of like if you bottle conditioned for a few weeks and then just opened one up without ever putting it in the fridge. You'll get a gusher.........and mostly flat beer. The same bottle chilled for 3+ days pours as it should.

 

[kenc_zymurgy]

...
With your advice on chilling for 3 days, I'm inferring that a lot of the co2 will get absorbed into the beer .... ?

Yes on the cartridge (or other CO2 source for dispensing), but actually, I do not think that the beer 'absorbs CO2 as it is chilled'.

Look at a CO2 volume/pressure chart. At room temperature, you will be around 30 PSI in there at 2.5 volumes. The beer will foam at that pressure and a typical line length for chilled beer.

But chill that beer to 38F, and the pressure will be at ~ 10 PSI, and you should get a great pour with typical line lengths. I don't think any CO2 'moves' from head-space to beer when this happens, those pressures are just the result of the space that the CO2 takes up at different temperatures. I think the science is that as a gas warms up, the molecules gain energy and push further away from each other. They do that in the beer and in the headspace.

You can chill a bottle of beer in 15 minutes or so in an ice water bath. It will pour just fine and the carbonation will be as expected. I don't think you can get beer to absorb CO2 in a few minutes that easily, or people could force-carb their kegs in an hour or so w/o shaking.

When you drew a pint at room temperature, you 'blew out' all the carbonation as it went from 30 PSI to atmosphere. CO2 escaped in to the air, and it produced foam. That's why the beer was flat - the CO2 mostly all went elsewhere.

-kenc

 

[kenc_zymurgy]

Just out of curiosity, if you have a keg, why would you not force carbonate? I haven't naturally carbed anything since I got my keg setup.

I naturally carb my mini-kegs, and I know brewers who routinely naturally carb their cornies.

A) You aren't taking up any fridge space waiting for it to carb up.

B) Table sugar is cheaper than CO2 (include extra time/gasoline to your CO2 re-filler).

C) There might be some advantage to having the yeast scrub a bit more CO2 out, and the yeast might provide other benefits. Or not, I'm just throwing this out, I have no idea

-kenc

 

[beerluvva]

...I think the science is that as a gas warms up, the molecules gain energy and push further away from each other. They do that in the beer and in the headspace.

-kenc

Hi

Thanks for the explanation..., so, to sum up, let's walk through the life of my keg:

1. beer racked to keg with priming sugar

2. keg charged/evacuated/charged to rid oxygen, leaving CO2 in the headspace, keg at some initial pressure (I use cartridges, no gauge, no idea what pressure)

3. yeast eats and releases more CO2 into the headspace, pressure increases

4. At some terminal pressure, the CO2 is in the beer and in the headspace. (I have heard 30 psi for bottling, which I think you have cited above)

5. if you attempt to serve at this same temp, the release of high pressure to atmosphere causes the CO2 in the beer and the headspace to rush out, making much foam and leaving almost no CO2 in the beer.

6. if instead, you chill the keg for some period of time, the CO2 pressure reduces. At this new pressure, a new balance of CO2 between headspace and beer will be reached, but as opposed to step 3, at this point there is CO2 in the beer

Is this close ?

(Have to go man the grill, happy 4th to the U.S.A crew !)

BTW, I took a pint (maybe two) from the keg in question after just 24 hrs in the fridge, and already seeing the benefit!

 

[kenc_zymurgy]

Pretty close, as far as I know, but I'm not too good with chemistry stuff. If you say 'mole', I think of mouse-like creatures, or a tasty Mexican-style sauce.

Not really that important to this, but in step 3, I've seen some debate about whether the yeast produce CO2 faster than it is absorbed by the beer. If they do, then the CO2 would go into the headspace and it would take some time for the beer to absorb it to hit equilibrium at that temperature.

In step 6, (again, as far as I know) it isn't really a 'new balance'. If the CO2 was at equilibrium at 70F, it will be at that same equilibrium at 38F. Only the pressure (and temperature) has changed.

So in both cases, there is the same amount of CO2 in the beer. But at 70F, the pressures will be much higher, and trying to draw 70F beer @ 30 PSI with a tap set up for beer at ~10 PSI will create massive foaming, and a fast spray. The sudden reduction in pressure from 30 PSI to atmosphere drives the CO2 out of the beer, resulting in lots of foam and pretty flat beer in your glass.

But closer to 10 PSI, the flow is much slower, so far less CO2 is lost as you draw. I just poured a sample from a mini-keg that I put in the fridge yesterday. I checked pressure after it chilled and before I hooked up gas, and it was right ~ 12 PSI. I'm sure it was at 30 PSI at room temp (I've measured it before, but not this time). The first pour was perfect, and tasty.

It will go well with our ribs later today. Happy 4th to you too!

One more thought popped in my head - imagine two little balloons, inflated to 30 PSI and tied shut. Tie one up under the beer in the keg, and one in the headspace. As you increase pressure in the keg, the balloons will be compressed, and if you release pressure, they expand. No real difference in the one under the liquid and the one in the headspace - the pressure is about the same on both. I picture that those balloons are acting the same as the CO2 - just expanding and compressing the same in the beer as in the headspace.

Maybe a real scientist can pop that balloon analogy, but I think it's pretty close. Ribs are calling!

-kenc

 

[beerluvva]

This makes sense to me, thanks for all the explanation!

 

[BrewKnurd]

In step 6, (again, as far as I know) it isn't really a 'new balance'. If the CO2 was at equilibrium at 70F, it will be at that same equilibrium at 38F. Only the pressure (and temperature) has changed.

So in both cases, there is the same amount of CO2 in the beer.

There is definitely a new equilibrium point when you change temperature, as the solubility of gas in liquid increases as temp decreases. So when you chill a keg, you have two effects. One is that the gas exerts less pressure as it cools, thanks to lower molecular energy, and this would happen in an empty keg as well as a keg with liquid. But additionally, a greater percentage of the total co2 in the keg well end up in the liquid once equilibrium is reached. This further serves to lower the pressure, as there are now fewer gas molecules in the headspace.

 

[mattd2]

I think of it similar to kenc
The beer has the same amount of "fizz" (i.e. dissolved CO2) at any temperature - if it has 2.5 volumes at 70°F it has 2.5 at 38°F. But to get that amount to disolve into the beer you need a higher pressure at a higher temperature. When you cool the keg down a little bit of that high pressure headspace CO2 will dissolve into the beer but it will be a minimal amount.
The problem with pouring a sample at room temperature is that once the beer is in your glass,or heading towards it in the hose, (i.e. at 0 PSIg) the CO2 escapes from the beer much "quicker" at 70°F than it does at 38°F resulting in more foaming (look at the charts at 1 PSIg the volumes are: 1.52 @ 38°F and ~0.75 @ 70°F = more CO2 will stay in the beer when it is colder) - really this should be more CO2 escapes. This adds to the issue mentioned above that serving beer at 30 PSI with a tap setup for 10 PSI will mean the beer will shoot out super fast.

 

[kenc_zymurgy]

There is definitely a new equilibrium point when you change temperature, as the solubility of gas in liquid increases as temp decreases. So when you chill a keg, you have two effects. One is that the gas exerts less pressure as it cools, thanks to lower molecular energy, and this would happen in an empty keg as well as a keg with liquid. But additionally, a greater percentage of the total co2 in the keg well end up in the liquid once equilibrium is reached. This further serves to lower the pressure, as there are now fewer gas molecules in the headspace.

Thanks for the added info. Do you have any idea how big the second effect is for beer going from 70F to 38F? I'm assuming it is a pretty small effect?

-kenc

 

[BrewKnurd]

Thanks for the added info. Do you have any idea how big the second effect is for beer going from 70F to 38F? I'm assuming it is a pretty small effect?

-kenc

CO2 is in the neighborhood of twice as soluble in water at 38 degrees vs 72 (an effect you can also see, although usually not all the way up to 72 degrees, on keg carbonation charts). How much of an impact this has on the pressure in the keg will be a function of how much headspace there is in the keg. A full keg with lots of liquid and very little gas space would show a much bigger impact on pressure as additional CO2 dissolved than a keg that was nearly empty. I've not done any of the math to figure out what the actual pressure change based on this increased solubility alone would be.

 

[Frige]

Hey man, pony up and get you a tank and regulator. Anit no reason to try to reinvent the wheel. Your life will be much easier, you will lose weight, grow more hair, and have more sex appeal.