Warm carbing - sanity check please

[Kealia]

For some reason I just can't get my head around this today and could use help from those smarter than me (read: everybody else here).

I have a keg that I just filled that won't get into my kegerator for a few weeks. While it's conditioning I want to carb it (but not naturally....jsut don't want any more trub). I'm going to carbing at about 60 degrees or so and I'm targeting the typical 2.5 volumes.

As such, I should set the regulator at 22/23psi. With the normal set-and-forget method I should be there in 10-14 days.
Here's the kicker that it making my head hurt:
If I disconnect the gas and then put it in the kegerator disconnected for a few days, where will I end up?
If I were to keep the 22/23 psi on it at 39 degrees I'd end up at about 3.5 volumes which is obviously WAY too high. But off the gas, how will it equalize? More CO2 absorbs at colder temps so I assume some of the CO2 in the headspace is going to get absorbed until it re-equalizes but at what volume will that occur?
I could bleed off the pressure when I put it in the kegerator but I still don't know where I'l lend up.
Surely we have a chemist/scientist here that can figure this out? Or at least somebody that can take an educated guess?

This is just one of those things that I can't seem to get a handle on.
My other option is to just set it at 12 psi (which is where I have my kegerator) and let it carb up to about 1.75 vols at 60 degrees before putting it in but now I really want to know the answer to my question.

Thoughts?

[Beer-lord]

I've actually wondered this myself. What I normally do if it's just going to be a week or two at room temp (70 here) is hit it with 30 psi for a few minutes then disconnect and leave it alone until it goes in the kegerator. Now, that doesn't help you drink it faster as I normally need 4 more days at 12 psi in the kegerator to be even close after doing this, its not perfect.

Once you take it off gas and chill it, I'm not sure if there will be enough pressure to force what's already in the keg into the liquid to carb it. But, that's just a guess on my part.
I would love to have shown you that I'm smarter than you but it just ain't so. Stand in line behind me.

[braukasper]

I often keg a couple, four points high when I know it will sit that long. gives it a bit of a carb only needs a day or two in the keg frig.

[Kealia]

I often keg a couple, four points high when I know it will sit that long. gives it a bit of a carb only needs a day or two in the keg frig.

So, you're carbing at room temp and then dropping the temp?

I would love to have shown you that I'm smarter than you but it just ain't so. Stand in line behind me.

Yeah, like we needed you to tell us that.

Seriously though, I'm sure there is an easy answer that I jsut can't see right now. Or maybe it's not an easy answer. I dunno.
It's like a damn word problem from 8th grade math, though. Grrrr.

[Rebel_B]

'I could bleed off the pressure when I put it in the kegerator but I still don't know where I'l lend up.'
My educated guess would be to bleed off the pressure till it is around 12psi when you put it in the kegerator. Let us know what you end up doing.... I have found myself carbing at 12psi, then dialing it down a little for around 8psi for dispensing.

[John Sand]

I'm doing the same thing right now. And I haven't researched it, nor did I study physics. But you are mixing your measurements I think. The higher psi would be lower at a lower temp because it contracts. The volumes/psi ratio changes with temperature, but the mass of the gas (volumes) remains the same.

[Kealia]

But there's no way to tell how much I'd be bleeding off. If I carb to 22psi when warm and then pull the relief valve a few times I'm only relieving the head space pressure. The beer may lose some pressure and drop from 22psi, but there's no way to tell it's dropped to 12psi. And that would require multiple bleed offs and may never actually drop that low because more is being absorbed in the cold beer than in the warm beer.

[Kealia]

I'm doing the same thing right now. And I haven't researched it, nor did I study physics. But you are mixing your measurements I think. The higher psi would be lower at a lower temp because it contracts. The volumes/psi ratio changes with temperature, but the mass of the gas (volumes) remains the same.

Unless we are talking about different things, the measurements are right. CO2 absorbs into cold liquids easier so you need less psi.

[Rebel_B]

If you are carbed to the correct 2.5 volumes at the warmer temp, you won't lose that by lowering the temperature when it goes in the kegerator.

[braukasper]

You got a spunding valve? I need to make one. Essentially it is an adjustable pressure relief valve. You would set to a couple of pounds more than you need and let nature take care of it. Adding a gauge will give you an exact reading. I have seen them on some OLBS. They are not to expensive.

[mashani]

If you are carbed to the correct 2.5 volumes at the warmer temp, you won't lose that by lowering the temperature when it goes in the kegerator.

This is true, but Henry's law says that some of the non absorbed CO2 in the headspace (which can't be absorbed at the higher temperature) is going to get absorbed once the temperature falls, so the actual CO2 volumes in the liquid could increase once it's chilled, if there is any pressure still in there when it's off the gas. Henry's law has all the math you need to figure it out, but you'd need to know how pressurized the headspace actually is once the gas is off. And I honestly have no clue there.

[Kealia]

That's exactly my thinking. If its going to require me to look up Henry's Law and do a lot of math I may just set it at 12 and call it good. That's a lot of work.

[FrozenInTime]

Gas chart I use.

[RickBeer]

When I read threads like these I smile - and state again in my mind that bottling isn't so bad.

I don't even have to calculate bottles since my spreadsheet has it done for me.

1/8/2015 empty bottle inventory

Quan Size Ounces
16 16.9 270.4
2 33.8 67.6
45 12 540 clean
8 16 128 clean 16 glass 3.493055556 clean cases
119 12 1428 to be cleaned
0 16 0 to be cleaned
164 12 1968 total 12 oz bottles (excludes gifts)
8 16 128 total 16 oz bottles
2434 ounces (excludes gifts)

1.6 5 gallon batches of cleaned bottles
3.8 batches I could bottle if I cleaned bottles
8.45 total cases of empties excluding gifts
72.0 1 liter bottle equivalency
144.0 1/2 liter bottle equivalency

[jimjohson]

well Rick I ain't got to figure bottles either, as I bottle 24(12oz) and keg the rest. however I don't force prime either, "bottle carb" works just fine in a keg and the pipeline is already set up for the wait.