Letting a carbed keg sit

[archthered]

I must admit that kegging is one of the biggest holes in my homebrew knowledge, I know I need to read more etc but I'll get there eventually. Any way, I only have room for 2 kegs in my fridge, I have two beers that I'm drinking (they are off the gas now and warm) and two beers that I'm carbing for an event. Once the two for the event are at the right carb level can I take them off the gas and let them sit so I can put my drinking beer back on and chill them? How will it affect things if I let it sit at room temp? I plan on pulling it out and letting it sit and then the night before the event put it back on the gas and in the fridge so it's cold, I'm concerned the carb level will be off. I am having some friends over the day before the event and would like to have beer that isn't for the event available, though I'd rather drink warm beer or even not homewbrew beer than ruin the carb level for the event.

I think it will be OK because although CO2 will be released as the beer warms this will raise the pressure in the kegs slowing the release and since it's not escaping the correct amount of CO2 will be there when I rechill it, while the higher pressure will allow the CO2 to reabsorb into the beer pretty quickly. My concern is that it will degas quickly but take a much longer time to reabsorb.

In short I think as long as it has the right amount of gas when it comes off and warms up all the gas will go back in at the right level when it is chilled back down. But is that right? Will 12-24 hours of chill time be enough to get the CO2 to go back into the beer? If this won't work would it work to take them off the gas put the kegs in my mashtun and hot liquor tank (10 gal coolers) and then cover them with ice in the mean time or does this risk going the other direction with it and making it too cold etc?

Thanks for any help

 

[DVCNick]

I've never done this, so just basing my opinion on knowledge of how I think it should work.

I think it would be fine to let the keg warm up and then re-chill and keep the right carb level, as long as your kegs have a perfect seal. If they have a very slow leak that you are not aware of, they will be losing gas, and will be losing it at a faster rate as they warm up and the headspace pressure increases.

If you have the ability to easily keep them cold(er) with an ice bath, I'd probably do that also, but if not, 24hr of chill time is probably fine, or it would be in my kegerator.

If the keg is perfectly sealed it should just behave like a really big bottle.

 

[Vale71]

If your keg is perfectly sealed you will not lose any CO2. The good thing about corny kegs is that they tend to seal better the higher the pressure so that's a good start.
As for CO2 going back into the headspace and then being reabsorbed your assessment is correct, apart from the fact that CO2 goes into solution as fast as it comes out for a given temperature as it's a perfectly symmetrical reaction. If your kegs are filled to nominal capacity there won't be much headspace for the CO2 to escape to before a new equilibrium is reached, so the amount of CO2 that will actually move to and from the headspace is only a small fraction of the total CO2, which means it won't take that long to reach a new equilibrium. Cooling time might be an issue though, so I would actually put the kegs in the keezer at least 48 hours before serving.

 

[9Kegs]

Have you considered priming in the keg? This would allow carbonation at room temperature and enjoying drinkable beer simultaneously. Only drawback is the clarity of the beer, but certain styles shouldn't be a problem.

 

[archthered]

I've never done this, so just basing my opinion on knowledge of how I think it should work.

I think it would be fine to let the keg warm up and then re-chill and keep the right carb level, as long as your kegs have a perfect seal. If they have a very slow leak that you are not aware of, they will be losing gas, and will be losing it at a faster rate as they warm up and the headspace pressure increases.

If the keg is perfectly sealed it should just behave like a really big bottle.

I've never experienced any issues with leaks, or are you suggesting we all probably have small leaks we simply aren't aware of because of how slow they are? I did you food grade keg lube on all connections and seals.

As for CO2 going back into the headspace and then being reabsorbed your assessment is correct, apart from the fact that CO2 goes into solution as fast as it comes out for a given temperature as it's a perfectly symmetrical reaction. If your kegs are filled to nominal capacity there won't be much headspace for the CO2 to escape to before a new equilibrium is reached, so the amount of CO2 that will actually move to and from the headspace is only a small fraction of the total CO2, which means it won't take that long to reach a new equilibrium.

So my question with that is why does it take so long to carb in the first place? My thought is that it is because there is quite a volume of CO2 that needs to be dissolved initially (like 1-2 volumes) where as in my case, as you said, very little CO2 is actually coming out of solution so very little has to reabsorb. I'm just making sure I'm understanding so I can use thid info later if needed/relevant.

Have you considered priming in the keg? This would allow carbonation at room temperature and enjoying drinkable beer simultaneously. Only drawback is the clarity of the beer, but certain styles shouldn't be a problem.

That is a brilliant idea... but also useless at this point. I started carbing the beer 4 days ago and have no idea how much CO2 it has absorbed so I have no idea how much sugar to add. If I was smart enough to ask this question before starting I would have gone with that method!

 

[Vale71]

I've never experienced any issues with leaks, or are you suggesting we all probably have small leaks we simply aren't aware of because of how slow they are? I did you food grade keg lube on all connections and seals.

I'm not saying that but leaks are always a possibility.

So my question with that is why does it take so long to carb in the first place? My thought is that it is because there is quite a volume of CO2 that needs to be dissolved initially (like 1-2 volumes) where as in my case, as you said, very little CO2 is actually coming out of solution so very little has to reabsorb. I'm just making sure I'm understanding so I can use thid info later if needed/relevant.

That is correct.

That is a brilliant idea... but also useless at this point. I started carbing the beer 4 days ago and have no idea how much CO2 it has absorbed so I have no idea how much sugar to add. If I was smart enough to ask this question before starting I would have gone with that method!

I'll let you in on a small secret. Contrary to popular but wrong opinion, force carbing is faster at high temperatures, provided of course that you set the correspondingly higher pressure needed according to the usual carbonation tables. So if you're in a hurry you might want to try first carbing and then cooling, not the other way around.

 

[BeerFst]

I'll let you in on a small secret. Contrary to popular but wrong opinion, force carbing is faster at high temperatures, provided of course that you set the correspondingly higher pressure needed according to the usual carbonation tables. So if you're in a hurry you might want to try first carbing and then cooling, not the other way around.

Why? the solubility of gas also goes down as the temperature increases. So for two points on the same carb chart, lets say 30PSI/70 degrees, and 12PSI/38 degrees, the rate of carb should be the same.

Are you saying the solubility decreases less with temperature than it increases with pressure? if so I'd love some references to the effect.

 

[Vale71]

Solubility is a property describing the equilibrium (or steady) state. It has no relationship with how fast that state is reached.

The rate at which equilibrium is reached is a dynamic property and like the rate of most physical-chemical reactions it is directly proportional to temperature, as higher temperature implies more available energy. In actuality this is due to the diffusion rate of the gas in the liquid, as absorption (or conversely, release) of the gas can only happen at the gas-liquid inteface and uniform distribution of the gas will then happen through diffusion over the concentration gradient, until equilibrium is reached (steady state). The diffusion coefficient is directly proportional to temperature and as diffusion is the limiting factor in gas absorption into the liquid this property is carried over.

Let me try and convince you with a simple practical observation. Everybody knows that if you let a lukewarm beer sit in the glass it will lose its carbonation much faster than if the beer were ice cold. When you force carb your beer is doing the same, only in the opposite direction, i.e. of increasing carbonation. How could the reaction rate have a different and opposite relationship with temperature based on the direction of the reaction? This would imply that the diffusion rate of the gas in the liquid increase both with increasing as well as with decreasing temperature which is clearly absurd. QED.

 

[Tbagger]

You will be fine. I recently carbed 22 kegs over the course of about 9 months months for my wedding earlier this year. After they were carbed to the level I wanted, I took them off gas and stored them. On the day of the event, after re-chilling them for about 4 days, they were perfectly carbed and ready to drink.

 

[archthered]

Solubility is a property describing the equilibrium (or steady) state. It has no relationship with how fast that state is reached.

The rate at which equilibrium is reached is a dynamic property and like the rate of most physical-chemical reactions it is directly proportional to temperature, as higher temperature implies more available energy. In actuality this is due to the diffusion rate of the gas in the liquid, as absorption (or conversely, release) of the gas can only happen at the gas-liquid inteface and uniform distribution of the gas will then happen through diffusion over the concentration gradient, until equilibrium is reached (steady state). The diffusion coefficient is directly proportional to temperature and as diffusion is the limiting factor in gas absorption into the liquid this property is carried over.

Let me try and convince you with a simple practical observation. Everybody knows that if you let a lukewarm beer sit in the glass it will lose its carbonation much faster than if the beer were ice cold. When you force carb your beer is doing the same, only in the opposite direction, i.e. of increasing carbonation. How could the reaction rate have a different and opposite relationship with temperature based on the direction of the reaction? This would imply that the diffusion rate of the gas in the liquid increase both with increasing as well as with decreasing temperature which is clearly absurd. QED.

So in short, although cold liquid can physically hold more gas at a given pressure and temp, absorption of CO2 happens faster at higher temps, meaning that increasing the pressure in a warmer liquid (beer) allows you to compensate for the colder liquids ability to hold more and speed up kegging time.

This is great, this is one of the things I've struggled with, I've got some chemistry under my belt (but a long time ago and I often don't always trust what I think I remember) and this all makes sense with what I thought I knew, as I said I haven't had a chance to go back and really dive into carbing and the physics/chemistry of it. I was partially confused because so many people swear by carbing cold or at least slowly at serving pressure and struggle with the various fast carbing methods. I have a feeling the issue for so many with fast and warm carbing is that it is easy to do that incorrectly and then have to deal with over carbed beer while cold and slow is just set and forget, making it hard to screw up.

Thanks