"Two weeks in the cool so the co2 is absorbed by the beer"

[Bernie]

If a well sealed beer is warmed then any CO2 coming out will increase the overpressure in the headspace so it won't outgas too much. At that point I would think that there's not much CO2 to go back into solution once it's cooled again.

 

[NickW]

The "2 weeks in the cold" isnt necessarily necessary to help the beer absorb the co2 (because of the limited headspace in the bottle)

Not quite, it has nothing to do with the headspace. It has everything to do with the dynamics of the secondary fermentation and the pressure created in the closed system at fermentation temperature. The cold conditioning will not affect the serving carbonation of your beer whatsoever, only the temperature at which you serve it will.

Cold conditioning is obviously beneficial for the beer in terms of clarity and the conditioning / mellowing out of flavours..

Almost certainly.

It was simply my understanding that beer will absorb CO2 quicker if it's colder, because of the relationship between pressure and temperature. How much quicker, I don't know.

Maybe, but that's not really the point. At any given temperature (and thereby pressure in a closed system) an equilibrium is pretty rapidly established whereby a finite volume of gas is in solution. This will not take weeks, while I don't know for sure, I'd say minutes or hours.

If *I* could summarise:

It is good practise to cold/cool condition your beer but it has nothing to do with the solubility of CO2 and everything to do with other physical, chemical and biochemical processes that make your beer look and taste better.

Thanks Calum... that clears it up quite nicely I think :thumb:

 

[calumscott]

that clears it up quite nicely I think

I do hope so... Thanks for putting it out there though, it's never sat comfortably with me but equally I'd never given it enough thought until you posted. :thumb:

 

[NickW]

Yeah it always sort of bothered me seen as I never had any trouble with commy beers. And they obviously sat in ambient supermarket temperature for weeks and sometimes months on end

 

[morethanworts]

The cold conditioning will not affect the serving carbonation of your beer whatsoever, only the temperature at which you serve it will.

At any given temperature (and thereby pressure in a closed system) an equilibrium is pretty rapidly established whereby a finite volume of gas is in solution. This will not take weeks, while I don't know for sure, I'd say minutes or hours.

Perhaps I don't understand Calum, sorry! If I take a bottle which has been primed and kept warm for (say) a couple of weeks, nicely pressurised from its secondary fermentation, are you saying that only the serving temperature will have an effect on the carbonation from that point on? So there is no further benefit or change in the carbonation (as opposed to other aspects of maturation) from that point onwards?

If so, I can only say that's not been my experience. The carbonation seems to develop more 'bite' as time goes on, bigger bubbles, less 'foamy' feel in the mouth, with all else equal.

 

[PaulCa]

My take on this is that it's all about the equilibriums.

The lower the temp, the more CO2 can be dissolved into the beer. BUT, it doesn't happen instantly. It takes time to reach equilibrium.

Opening bottles or cans, or dispensing from a keg involves a sharp shock change to the pressure, dropping it by 10 PSI or more instantly. This causes the beer itself to expand! (Liquids DO compress when they contain dissolved gas). This sudden shock expansions starts off the process of bubbles forming and rising which causes more bubbles to form and rise and the all too familiar run away degassing and spray of foam. It exactly the same as if you dropped a cold can before opening it, it will spray due to the pressure shock from being dropped upsetting the equilibrium.

If the bottle is at 15 PSI at room temp where it has been carbing, and you then lower the temp to 2*C and wait for a number of days for it to reach equilibrium, the pressure will have fallen to quite low, maybe 2 or 3 PSI. Thus when you now open it, there is much less shock and the degassing doesn't go run away. Over carbing it will make spraying inevitable as even at 2*C the beer simply cannot hold that much CO2 at ambient pressure and the degassing accelerates rapidly until it sprays everywhere.

2 weeks is a bit extreme though, I expect 2 days might be enough. Maybe less.

 

[morethanworts]

I meant 'two weeks (say)' for the yeast to eat up the sugars and produce the gas, not two weeks to 'reach equilibrium', for the gas to be 'absorbed' or whatnot. I have little idea on the science of that - which is why this thread is of interest.

 

[calumscott]

The cold conditioning will not affect the serving carbonation of your beer whatsoever, only the temperature at which you serve it will.

At any given temperature (and thereby pressure in a closed system) an equilibrium is pretty rapidly established whereby a finite volume of gas is in solution. This will not take weeks, while I don't know for sure, I'd say minutes or hours.

Perhaps I don't understand Calum, sorry! If I take a bottle which has been primed and kept warm for (say) a couple of weeks, nicely pressurised from its secondary fermentation, are you saying that only the serving temperature will have an effect on the carbonation from that point on? So there is no further benefit or change in the carbonation (as opposed to other aspects of maturation) from that point onwards?

If so, I can only say that's not been my experience. The carbonation seems to develop more 'bite' as time goes on, bigger bubbles, less 'foamy' feel in the mouth, with all else equal.

That's right, my assertion is that if you take one bottle and do 2 warm then 2 cool then, lets say a further day cool then a second bottle 4 warm and 1 day cool you will notice no difference in carbonation. Well, no, actually there should be no difference in the volume of CO2 dissolved in your beer. Your *perception* of carbonation may be different between the bottles.

The cooled one may well be clearer as the yeast may have dropped out more fully and who knows what yeast does to the way the CO2 comes back out of the beer when poured... other chemical changes will have happened differently between the bottles which again, may affect the bubble formation, head retention etc. but still, at the point of opening the bottle, the volume (or mass if you are being picky) of CO2 in the beer will be the same between the bottles. :thumb: