To Pre-Chill or Not to Pre-Chill

[3 Dawg Night]

That is the question.

I haven't been able to find this exact issue addressed on HBT. Cold liquid absorbs CO2 more readily; got that. But, is it really necessary (or even beneficial) to chill before hooking up the gas?

Example
I have a Belgian Pale Ale that has reached terminal gravity and is sitting in my fermenter at 72F. My keezer is set to 38F. I plan to put it on 11psi to get ~2.5 vols.

Should I:
a) Rack to the keg, chill overnight, then hook up the gas, or
b) Rack to the keg, hook up the gas, and let it carb while chilling.

Let's think through option a.
1) My CO2 regulator will pressurize the keg to 11 psi.
2) My 38F beer will absorb some amount of CO2, and my regulator will continue to equalize the pressure in the keg.
3) My beer will continue to absorb CO2 until it equalizes at 11psi.

Now let's consider option b.
1) My CO2 regulator will pressurize the keg to 11psi.
2) My 72F beer will absorb some amount of CO2.
3) As the beer cools, it will be able to absorb more-and-more CO2, and my regulator will continue to equalize the pressure in the keg.
4) Once the beer reaches 38F, it will continue to absorb CO2 until it equalizes at 11psi.

So, I'm not seeing the benefit of one method over the other. There's no danger of over-carbing, because the beer will be able to absorb more CO2 as it cools.

Can anyone tell me why I would want to pre-chill my beer before force carbonating?

 

[AlexKay]

I agree with your assessment; namely, that it doesn't matter.

 

[Jayjay1976]

Yikes.

 

[Sammy86]

Should I:
a) Rack to the keg, chill overnight, then hook up the gas, or
b) Rack to the keg, hook up the gas, and let it carb while chilling.

This...nothing bad is going to happen while on CO2

 

[3 Dawg Night]

Yikes.

Can you expand on that point?

 

[Jayjay1976]

Can you expand on that point?

I could.

 

[Jayjay1976]

Can you expand on that point?

Hey Huntsville! I'm from Bear Creek! Hallo friend!

 

[micraftbeer]

Do option b. You'll just miss out on time carbing the beer at the less ideal temperature. You'll still absorb some CO2, so no point to wait.

Plus if you waited, you'd probably have a post that reads, "Doh! I forgot to hook up my beer to the gas and it's been sitting here for 2 weeks, completely uncarbonated!"

 

[3 Dawg Night]

I could.

Then help a North Alabama brother out.

 

[Ridenour64]

Has anyone recommended chilling prior to hooking up gas? I don’t see how it would matter.

 

[3 Dawg Night]

Has anyone recommended chilling before carbonating? I don’t see how it would matter.

When I started kegging (about four months ago), my research led me to several sites that said "ALWAYS CHILL YOUR BEER BEFORE CARBONATING." But, no one offered any reasons why.

Just a few examples:
https://www.brewcabin.com/force-carbonation/https://learn.kegerator.com/force-carbonating-beer/https://chme.nmsu.edu/files/2016/06/Brite-tank-carbonation.pdf

 

[Ridenour64]

I skimmed through one of the links. If your going to set and forget, then i don’t think it matters when you hook up your CO2. If your going to force carbonate by agitating your keg, that’s best done when cold because the beer will absorb CO2 at a more rapid rate.

 

[3 Dawg Night]

I skimmed through one of the links. If your going to set and forget, then i don’t think it matters when you hook up your CO2. If your going to force carbonate by agitating your keg, that’s best done when cold because the beer will absorb CO2 at a more rapid rate.

That's probably the best answer I've seen.

 

[madscientist451]

The best answer is:

RDWHAHB

 

[Pkrd]

You don't cold crash?

 

[jerrylotto]

When you chill your beer in any closed vessel, the head pressure is going to drop as the gas inside cools. If you are not at a positive pressure beforehand, you would pull a vacuum. But keg posts are not made to hold vacuum, they are designed to retain positive pressure - so you would instead probably pull air inside. Why go through all of the machinations of closed transfer only to screw up your beer when cold crashing? I always pressurize BEFORE chilling to make sure that there is no air ingress and oxygen exposure. Even better, hook the keg up to your tank before chilling and you will be assured of a positive pressure.

 

[T Murph]

I've been kegging for over 25 yrs and I always pressurize once I transfer to a pre-purged keg for the exact reason @jerrylotto explained above. I never chill first.

 

[Vale71]

That's probably the best answer I've seen.

Except it's wrong. Beer (or any liquid for that matter) absorbs gas faster the higher the temperature it's at.

 

[T Murph]

Except it's wrong. Beer (or any liquid for that matter) absorbs gas faster the higher the temperature it's at.

What?

 

[Vale71]

Most people confuse saturation (equilibrium condition) with the actual kinetics of gas dissolution and release.

Gas dissolution and release into/from a liquid are based solely on diffusion and gas exchange at the surface. Both processes have rates that are directly proportional to temperature, both because higher temperature means a higher energy state as well as because water's viscosity (the "braking factor") is inversely proportional to temperature.

 

[Ridenour64]

Please provide some application. Are you suggesting he should do this warm?

https://www.northernbrewer.com/blogs/kegging-bottling-techniques/how-to-carbonate-beer
“FORCE CARBONATION
Most carbonation in kegs is done using pressurized CO2 from a gas cylinder, a process called force carbonation. The fastest results can be achieved when the beer in the keg is at a cold temperature. This will let the CO2 diffuse into the beer more efficiently and at a faster rate.”

 

[ThatVideoKid]

Most people confuse saturation (equilibrium condition) with the actual kinetics of gas dissolution and release.

Gas dissolution and release into/from a liquid are based solely on diffusion and gas exchange at the surface. Both processes have rates that are directly proportional to temperature, both because higher temperature means a higher energy state as well as because water's viscosity (the "braking factor") is inversely proportional to temperature.

I guess the question would then be, can water hold 2.5 volumes of CO2 at 80F?

 

[Dland]

...

 

[Dland]

Does not go up to 80F, but one can extrapolate;

 

[Vale71]

I guess the question would then be, can water hold 2.5 volumes of CO2 at 80F?

Sure it can, you just need to be able to set the correspondingly higher pressure in order to reach the same saturation level at equilibrium.

Kegs are rated for pressure that are more than adequate to fully carbonate beer at ambient temperature. After all, that's the temperature commercial beer is usually stored at until it's time to start serving it. Back when I didn't spund but force-carbed in kegs I could see first hand that carbonating ales at ambient temperature using the set-and-forget method was at least twice as fast as the same process at lagering temperature.

Water's (and consequently beer's) viscosity is lowered by a factor of about 2 going from 0°C to 25°C plus there is a small increase in absorption and diffusion rates due to the increase in molecular kinetic energy (about 8%).

 

[Vale71]

“FORCE CARBONATION
Most carbonation in kegs is done using pressurized CO2 from a gas cylinder, a process called force carbonation. The fastest results can be achieved when the beer in the keg is at a cold temperature. This will let the CO2 diffuse into the beer more efficiently and at a faster rate.”

99% of the info you'll find online on this topic is just quoting the same incorrect information for the nth iteration and is unfortunately useless as a reference.

 

[Ridenour64]

I see. I have a beer I’ll be kegging in a few days and will try set and forget at room temp.

 

[Ridenour64]

Because we’re talking about carbing at room temp which will require higher pressures, I have a follow up. Does anyone know the pressure rating for our CMB ball lock fittings? My gas fitting will leak around 30 PSI but is fine when lowered.

 

[3 Dawg Night]

The best answer is:

RDWHAHB

Oh, I'm R'd, not W'ing, and H'd a couple of HBs. I just thought it was an interesting thought exercise.

 

[3 Dawg Night]

You don't cold crash?

No, I don't. It just seems (to me) like an extra step for little benefit.