To Pre-Chill or Not to Pre-Chill

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3 Dawg Night

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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?
 

micraftbeer

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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!"
 

Ridenour64

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

3 Dawg Night

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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:
 

Ridenour64

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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.
 
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3 Dawg Night

3 Dawg Night

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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.
 

jerrylotto

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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.
 

Vale71

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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

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


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

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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

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

1628259048379.png
 

Vale71

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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

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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

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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.
 
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3 Dawg Night

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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%).
I'm sort of thinking through this as I type.

So, warm beer will absorb CO2 more quickly than will cold beer, but cold beer will hold more CO2 than warm beer? Is that what we're saying? What are the implications of that? If I force carb (set-and-forget) at room temperature, the beer will equalize CO2 more quickly, but higher pressure will be required to push it into solution. Once I chill that beer, less pressure will be required to keep that CO2 in solution, but the same overall volume of CO2 is required. So, it appears that the only benefit to chilling first is that you can use a lower pressure (which is not really a benefit), and the benefit to carbing warm is that it will be carbed sooner.

Back to my original question, though: there's probably negligible difference in chilling before applying CO2 and letting it chill while carbing.

We're getting close to needing to move this to the Brew Science forum.
 
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3 Dawg Night

3 Dawg Night

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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.
I emptied a 20 lb CO2 tank that way last month. 😢
 

Romex2121

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When I read the OP’s question I knew this was gonna an interesting thread and I needed to pay attention, I to have wondered the same thing from time to time while transferring to keg.
The further it goes I can’t help but think about the eternal question of is the glass half full or half empty , LOL .
This is gonna be good ….
 
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Vale71

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Back to my original question, though: there's probably negligible difference in chilling before applying CO2 and letting it chill while carbing..
The latter will be a bit faster depending on how fast you actually chill the keg.

I think the most important point is that the reason most people quote for chilling and then carbing, namely that beer carbs faster at lower temps, is actually wrong and can be disregarded.
 

micraftbeer

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So it's maybe the wrong bit of the science that's referenced as the reason. The proper reason for chilling to carbonate is it doesn't require as high of a pressure to get the desired vols of CO2.

Higher pressure exposes you to potentially uncover a pressure capability weakness in your system, that otherwise wouldn't affect you when carbonating at a lower pressure. Like the above-referenced experience of inadvertently draining a CO2 tank through a leak exposed when running a higher pressure.
 

Murph4231

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I have lost way more CO2 due to hose clamp and disconnect 0 rings failing inside my cold chamber than at room temperature. Additionally I don't have to worry about a keg creating a vacuum and sucking O2 inside to taint my brew. I do it a little differently and spend more time doing it. I purge my keg after I sanitize it then give it a good shot of CO2 before doing a closed system transfer. Then I pressurize it to around 20 psi for a few hours before putting it into the beer fridge. Then adjustments are made according to the specific brew at hand. This very well may be completed at cold temperature with a constant check on connection etc to ensure no leaks. Just last week I had a liquid quick connect decide to start leaking in the fridge. Fortunately due to checking often, I found the leak before the entire 20lb tank was emptied.
 
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Since I dry hop in the keg, my process has become:

move beer into pressurized and purged keg (hops already in it),
purge the remaining space a few times to make sure it's still pressurized and any O2 that might be in there gets vented out,
move keg to the keezer to cold crash and dry hop at 36F,
then after 2 days I put it on gas to carbonate and knock the remaining hops and yeast out of solution to the bottom.

I use a beer float, so I don't normally get any hops in the glass until the last pint. Also, when I put it on gas, I bump the pressure up to 30PSI for a day for two, before dropping it down to serving pressure. I don't rock or shake it, but it still speeds up the process by several days compared to set-and-forget.

What is the adage? Ask 2 brewers, get 3 opinions?
 

ThreeSheetz

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The latter will be a bit faster depending on how fast you actually chill the keg.

I think the most important point is that the reason most people quote for chilling and then carbing, namely that beer carbs faster at lower temps, is actually wrong and can be disregarded.
Hmm... good to know.
'cause I was "taught" that gas and liquid do depend on temperature but were inverse. Warm air held more moisture and cool liquid held more gas. Please note I am not arguing your point. I'm just someone who goes by what they read.
Although, I have noticed when I bottle beer, I carbonate it in the bottle using my fermentation chamber, but in order to get the CO2 into solution, I need to refrigerate it for at least 24 hours.
Again, no arguing, just stating my observations.
 

Brooothru

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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.
Good analysis, but the best way (in my view) is to slap a spunding valve on the Gas In post when gravity is about 5 points from predicted final gravity. Set the release point at about 15 psig and let it finish fermentation at room temperature. Leave it be for 5~7 days and put the keg in a kegerator or beer fridge to condition and/or lager.

Pressure will drop with temperature to somewhere around 10~12 psig. No worries about suck back or oxygen exposure. You can adjust keg pressure up or down for your serving preferences.

Either serve from that keg (first 2-3 glasses should get most of the sediment. Or get fancy with a floating dip tube and get clear beer on the first pull.
 
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