[petermmitchell]

Last night I tested force carbonating 2 kegs for 24hrs at 40 psi.  This evening when I checked one of the them was nicely carbonated, which I am quite pleased with The other keg is noticeably less carbonated.  It's somewhat carbonated with larger bubbles but not close to where the other keg is.  Any ideas on what could account for this? 

Temperature differences between the 2 would be pretty small I think?  I have a 14-15 cubic chest freezer with 4 other kegs in there so its not like one was in the center and the other was against the wall. 

I was pretty paranoid about co2 leaks being it was the 1st time I turned up the gas to 40psi.  I was thinking if there was a leak, the gas would be empty by the time I returned from work today, but it was fine and still holding at 40 psi the whole time.  Could there still be a leak somewhere?

[tonyccopeland]

Could it be the volume of beer in the kegs?  I have found my 3.5 gallon batches in 5 gallon kegs carb up much faster than my full 5 gallon batches.  I don't fully understand the science and how the CO2 is dissolved in solution, but I track volume and temp of the beer as well.

-Tony

[majorvices]

+1 - head space is probably the reason. The more head space the faster the co2 absorption.

[el_capitan]

I've noticed differences in keg carbing, and I think it ties in to oils at the surface of the beer.  For instance, my BVIP seems to carb really slowly and I think it's due to the vanilla oils.  I've had similar results with really hoppy IPA, where the hop oils could possibly create a somewhat impermeable layer at the top of the beer.  Purely anecdotal evidence though.

[Stevie]

+1 - head space is probably the reason. The more head space the faster the co2 absorption.

While I don't argue this isn't possible, I can't understand why it would be so. I do believe I've witnessed it my self as well. Only thing I can think of is the slow to carb keg is filled so full that it has affected the gas/beer surface interface, wouldn't the pressure on the beer always be constant?

[Philbrew]

+1 - head space is probably the reason. The more head space the faster the co2 absorption.

While I don't argue this isn't possible, I can't understand why it would be so. I do believe I've witnessed it my self as well. Only thing I can think of is the slow to carb keg is filled so full that it has affected the gas/beer surface interface, wouldn't the pressure on the beer always be constant?

I agree!  Intuitively I think that it's not so much head space (volume) as it is head surface area.  If one keg is filled to the normal top of the cylinder and the other is slightly overfilled to where the top tapers fast, the surface area will be very different.  And it's the exposed liquid area that determines co2 absorption rate.