Force Carbonating Then Dropping Temp

[b_thomas]

Have finally moved away from the bottles on to kegging (scored a fire extinguisher yesterday from work). I've got a question regarding force cabonation that's hopefully easily answered.

If I force carb using the slow method at a higher temperature (ie. 18c) and then drop down to serving temperature (ie. 5-6c) will the CO2 already absorbed at that higher temperature cause the beer to become more "fizzy"?

I'm assuming I would need to reduce the PSI once the beer is at serving temp if I want to maintain the same volume of CO2 in solution it's just the transition from the warmer temp that I don't want to bugger up.

I guess I can always burp the keg if it is too "fizzy".

 

[BjornJ]

hi mate
I think it is the other way around, that the beer will be able to absorb less CO2 at the higher temp.

That when you drop the temp you will be able to carbonate more and faster, so if possible drop the temp first and then carbonate.



Bjorn

 

[stuchambers]

I dont keg but my understanding is and I am willing to be corrected the beer will become less carbonated as you cool it down.
The liquid will accept more gas as the temperature is lowered.

Edit: need to be quick here

 

[bignath]

hi mate
I think it is the other way around, that the beer will be able to absorb less CO2 at the higher temp.

That when you drop the temp you will be able to carbonate more and faster, so if possible drop the temp first and then carbonate.



Bjorn

Yep, spot on Bjorn.

Also, the term "force carbonating" (whilst not being too specific) is generally accepted as pushing the gas in really quickly in a short time frame to get you up and drinking it sooner.
Technically, i guess it is force carbonating even if carbing at serving pressure, but most brewers i think, automatically assume a higher carbing pressure when the term "force" is used. Probably being way too pedantic, but just trying to save some communication down the track if someone has issues and is trying to get them resolved.
Whilst the only difference between "force" and "slow" carbing is assumption over the pressure used, the end results of both "assumed" methods can be very different.
ie: it's pretty much impossible to overcarb a "slow carbed" beer set to serve pressure over a week before it's used.
and it's pretty bloody easy to overcarb a "force carbed" beer set higher to save time.

Hope i'm making sense....

Nath

 

[Bribie G]

Yup, high school chemistry / physics. With bottling in PET you often have a firm feeling bottle that goes 'soft' in the fridge because it's not as highly carbed as you thought it was. Same principle.

 

[donburke]

you often have a firm feeling bottle that goes 'soft' in the fridge

the same principle as swimming in cold water

 

[argon]

Have finally moved away from the bottles on to kegging (scored a fire extinguisher yesterday from work). I've got a question regarding force cabonation that's hopefully easily answered.

If I force carb using the slow method at a higher temperature (ie. 18c) and then drop down to serving temperature (ie. 5-6c) will the CO2 already absorbed at that higher temperature cause the beer to become more "fizzy"?

I'm assuming I would need to reduce the PSI once the beer is at serving temp if I want to maintain the same volume of CO2 in solution it's just the transition from the warmer temp that I don't want to bugger up.

I guess I can always burp the keg if it is too "fizzy".

So you're not crash chilling before packaging then?
if it were me i'd be dropping the temp before packaging and carbing. This will serve 2 purposes,
1. you'll be dropping out yeast etc prior to packaging, and
2. it i'll be easier to carb to the required volumes as the beer will accept the co2 easier.

It's what i do, and probably what a majority of keggers do.

 

[b_thomas]

Understood about gases being more readily dissolved at lower temps which is why I'm asking.

If I dissolve 2.5 volumes of CO2 into liquid at 18c (roughly requires 25PSI) what happens when I drop the temperature of the liquid (at 5c it requires roughly 14PSI to get 2.5 volumes of CO2 in to the same amount of liquid)? There's still 2.5 volumes of CO2 in the liquid however when it comes back out of solution am I going to end up with a glass of foam or flat beer due to the change in temperature?

I think the best trick will be to make room in the fridge and carb once the beer is down to the temp I want to serve at. Less thinking and more drinking!

P.S. Bombed out of Chemistry at high school roughly around the time we started learning about gases and Moles

 

[unrealeous]

If I dissolve 2.5 volumes of CO2 into liquid at 18c (roughly requires 25PSI) what happens when I drop the temperature of the liquid (at 5c it requires roughly 14PSI to get 2.5 volumes of CO2 in to the same amount of liquid)? There's still 2.5 volumes of CO2 in the liquid however when it comes back out of solution am I going to end up with a glass of foam or flat beer due to the change in temperature?

That is correct - however, if you try and poor a beer from that keg at 18 degrees - all you'll get is a glass of foam. If you cool it to 2 degrees - it will be all good again.

The issue you'll have is how long to rock it for - Ross method suggest ~60 seconds when keg is cool - its bound to be different when keg is warm.

Suggest keep it simple as other suggest - cool first then carb.

 

[Nick JD]

1000 words. you can get twice as much in at 5C as at 25C. So yeah - start carbing at room temp, but I wouldn't bother trying to force carb warm.

 

[unrealeous]

What would be an interesting exercise is to find the temp at which you couldn't over carbonate your beer. eg - heat the keg to 55 degrees, shake the hell out of it for 2+ minutes with gas at 3bar - cool to serving temp - perfect pour. :icon_cheers:

 

[stuchambers]

I dont keg but this thread has got me thinking.
Can you really control the vols of CO2 in kegged beer or does it always just reach an equilibrium with your serving pressure.

In a bottle there is a sealed container and the CO2 produced is a result of the fermentation of sugar. Adding more sugar equals more CO2 a bottle being a closed system therefore the increase in CO2 pressure forces the gas in solution when we open the system ie. the bottle. We have changed the pressure gas comes out of solution we get bubbles in beer.

In the kegging system as I understand the system is always open as we are adding gas to serve with. Initially the forced carbed keg will be at higher pressure than the serving pressure however once you pour some beer there is more empty space above the beer this space is then filled with gas. If the partial pressure of the CO2 in the beer is higher that what is provided by the serving pressure the CO2 will be provided by the beer and not the gas bottle, this process will continue to happen until the two pressures are equal. The pressure of CO2 coming out of the beer and the pressure of CO2 being added by the gas bottle.

Much like when you open a soft drink and then replace the lid the gas comes out of solution and the bottle seems firm again but never quite as much as an unopened bottle. This process will continue until the CO2 is at equal pressure with that of the atmosphere. In the kegging example the atmosphere is the serving pressure provided.

Am I way off the mark here.

Cheers Stu

 

[argon]

correct... it will equalise in time. The trick is to get your system balanced, where your serving pressure is the same as the pressure required to give you your desired co2 volume

 

[stuchambers]

So unless you have different regulators all beers will be served with the same vols of CO2.
Do most people just choose somewhere in the middle or are there people that are drinking very fizzy stout as they have the pressure set for a Pilsner or verser vice people drinking flat pilsner as they more commonly drink ales or stouts.

Cheers Stu

 

[rangaz]

b_thomas
Force carbing only takes about 15mins once its cold (I connnect gas at slightly high pressure than required to the beer out and shake) and I can tell you its easier getting to desired volume at serving temp with lower pressures than trying to do it at room temp with higher pressures. Much less mess and beer shooting all over the place when you try to pull off the gas disconnect. Both will be carbonated to correct level when chilled to serving temp but trying to do it warm is so much harder

 

[argon]

So unless you have different regulators all beers will be served with the same vols of CO2.
Do most people just choose somewhere in the middle or are there people that are drinking very fizzy stout as they have the pressure set for a Pilsner or verser vice people drinking flat pilsner as they more commonly drink ales or stouts.

Cheers Stu

yep... just pick a middle ground and go with it.

I know some people keep a keg higher carbed (a wheat beer or soda water as an example) and put a non return valve to separate the keg from the rest. This extends the time before equilibrium. But unless you've got it on 2 different regs then you won't be able to maintain separate volumes.