Does the volume of beer in my keg affect the pressure needed to carbonate?

[Killobyte]

I wouldn't think so because the regulator will just fill whatever headspace is there with as much CO2 as it needs to achieve the set pressure, but I'm just making sure. My last brew came out to only ~4.5 gallons, so I want to make sure I don't need to turn the pressure up/down from what the calculator says if it assumes 5 gallons. Thanks!

 

[day_trippr]

Volume doesn't change the pressure required to achieve a specific carbonation level at a given temperature. Given the same surface area within the vessel (eg: a partially filled keg), what changes with the reduced volume is the time it takes to achieve saturation...

Cheers!

 

[BrewCrewKevin]

No, it doesn't.

Think of it this way. The amount absorbed into the beer is a function of a) surface area and b) pressure. Whether there is 1 gallon or 5 gallons in the keg, the surface area is the same. So that means the pressure also should be the same.

However, the reason it may seem confusing is because the less there is in the keg, the more gas you will use to achieve that pressure.

 

[audger]

No, it doesn't.

Think of it this way. The amount absorbed into the beer is a function of a) surface area and b) pressure. Whether there is 1 gallon or 5 gallons in the keg, the surface area is the same. So that means the pressure also should be the same.

However, the reason it may seem confusing is because the less there is in the keg, the more gas you will use to achieve that pressure.

+1

the confusion in this thread stems from a confusion between measuring "mass" itself, and measuring "mass-per-unit-of-area".

"Pounds" is a measure of mass.

"Pounds per square inch" is a measure of mass-per-area.

(see my post here)

 

[raouliii]

A large headspace may need a few extra pressure/release cycles to dilute the oxygen level down to an acceptable level. I usually perform around 4 cycles for a keg that is full to top of the vertical sides. YMMV

 

[GilaMinumBeer]

If this were the case then everyone would be arguing about what to set the regs at as the keg empties. Thankfully, it's a set it and forget it procedure at it's simplest.

 

[Howhownow]

Only reason it matters is if you are force carbing by shaking/rocking, without it being hooked up to the gas in line. More headspace means more available CO2 to force into solution (surface area doesn't matter with the shaking). This means the keg will carbonate faster/with less recharges from the CO2.