Planning and logistics

[Classic Brewing Co]

20 minutes ago, Shamus O'Sean said:

Hi Classic, In my experience a 1/2 full keg of beer on CO2 does carb faster than a full keg.  I leave a full keg at 40psi for 24 hours.  1/2 full kegs I either leave at 40psi for 12 hours or 20psi for 24 hours.  I think there is a relationship between pressure and time.  It probably relates to the surface area and volume of the beer in the keg.  I do not think that the headspace in the keg matters.  The relationship is not linear, because when you get down to a 9.5 L keg with 4 L of beer in it, my maths goes skewwhiff.  By that I mean it is probably not as simple as 40psi for 6 hours or 10psi for 24 hours.  For that small volume (4 L), I suggest using serving pressure for a day or two and give it a test each day until carbed to your satisfaction.

Cheers Shamus, thanks for your reply, in the morning I am putting it on serving pressure & trying it tomorrow night.

I guess it comes down to being patient. 

 

[kmar92]

1 hour ago, Shamus O'Sean said:

Hi Classic, In my experience a 1/2 full keg of beer on CO2 does carb faster than a full keg.  I leave a full keg at 40psi for 24 hours.  1/2 full kegs I either leave at 40psi for 12 hours or 20psi for 24 hours.  I think there is a relationship between pressure and time.  It probably relates to the surface area and volume of the beer in the keg.  I do not think that the headspace in the keg matters.  The relationship is not linear, because when you get down to a 9.5 L keg with 4 L of beer in it, my maths goes skewwhiff.  By that I mean it is probably not as simple as 40psi for 6 hours or 10psi for 24 hours.  For that small volume (4 L), I suggest using serving pressure for a day or two and give it a test each day until carbed to your satisfaction.

OK, now I am totally confused.

If the time required to carbonate is not affected by headspace, but is by surface area and volume, then the surface area does not change if the keg is full or half full. OK I think I see your point and it seems to be that the volume of beer to carbonate is the main driver - am I correct?

Sorry, doing a bit of thinking aloud

Edited February 1 by kmar92

[Shamus O'Sean]

9 hours ago, kmar92 said:

OK, now I am totally confused.

If the time required to carbonate is not affected by headspace, but is by surface area and volume, then the surface area does not change if the keg is full or half full. OK I think I see your point and it seems to be that the volume of beer to carbonate is the main driver - am I correct?

Sorry, doing a bit of thinking aloud

Do not take my word for it @kmar92.  I am just doodling ideas myself. 

It seems to me whether you have 2 centimetres of headspace or 2 metres of head space, the pressure in that headspace and at the surface of the beer is constant.  That is why I do not think the headspace is a variable.

I reckon the volume is the main variable/driver.  The CO2 has to dissolve into the beer.  The more beer there is, the longer it will take for CO2 to dissolve into it. 

You can change that up by using a carbonation stone on the end of CO2 dip tube going to the bottom of the keg.  So the CO2 bubbles up through the beer.  The outer surface of the bubbles, in effect, increases the surface area of beer exposed to the CO2.  Plus the bubbles are coming from the bottom so getting to the bottom of the keg quicker than pressurising from the top surface.

Similarly the rock 'n' roll method of carbonating a keg on its side and rolling it back and forward, increases the surface area exposed to CO2.  Hence why this method (which I have never done) is reportedly so quick.  But also why it is easy to over-carbonate using this method.

It would be good to here more detail from gas experts/scientists about this topic.  My ideas are just guesses, but seem logical to me.

[kmar92]

3 hours ago, Shamus O'Sean said:

It would be good to here more detail from gas experts/scientists about this topic.  My ideas are just guesses, but seem logical to me.

I agree, also seems logical to me.