Surface Area vs Headspace When Force Cabonating

[hinkensj]

I did a search on this subject and read Kilobyte’s post (https://www.homebrewtalk.com/forum/...sure-needed-to-carbonate.475712/#post-6146347) on a similar subject.

I have a bourbon barrel porter in my corny’s and it is taking forever to carbonate. (40F w/ 7-8 psi which should get me close to the 2 volumes I am looking for.) It’s been several weeks and it is still not fully carbonated.

I went to my LHBS to get a pressure gauge—I wanted to verify the pressure in the kegs was the same as I had set the regulator to. The lady there asked if the kegs were very full. In fact they are—or were before my taste testing... I thought for sure she was referring to the surface area of the beer exposed to the CO2 in th keg, but she said no. She said it is the amount of headspace that matters.

This doesn’t compute to me. Seems as long as I have the beer level low enough to maximize the surface area (and not so high that gets into the domed area of the corny) it shouldn’t matter how much headspace there is.

Thoughts?

 

[doug293cz]

You are correct, it is surface area exposed to CO2 that matters, not headspace. The lady at the LHBS was wrong. Here's a recent post I wrote that goes into more detail.

Brew on

 

[Vale71]

Did you mention to the lady that you were force carbonating? If you are priming a half empty keg will take longer to carbonate as the headspace will need more CO2 to develop in order to reach the target pressure. If the keg has too much headspace you might even end up with undercarbonation. Maybe the lady thought you were priming with sugar?

 

[hinkensj]

Did you mention to the lady that you were force carbonating? If you are priming a half empty keg will take longer to carbonate as the headspace will need more CO2 to develop in order to reach the target pressure. If the keg has too much headspace you might even end up with undercarbonation. Maybe the lady thought you were priming with sugar?

Yes. She knew I was force carbonating. We had even talked about the temp and pressure I am using. Using sugar would have the opposite effect she was talking about. As you mentioned, more headspace would likely slow the carbonation using sugar, but she thought it would speed the force carbonation...

I am in concurrence with the group here that is shouldn’t matter as long as the surface area is not changing.

 

[doug293cz]

To be clear, a half full keg and a full keg (with same surface area) will absorb CO2 from the headspace at the same rate. However, the half full keg only needs to absorb half as much CO2 into the beer, so will carbonate in about half the time, as a full keg. An over filled keg will take longer to carb, since once you get above the vertical side wall level, the surface area starts reducing very quickly.

Brew on

 

[RoseParkBrews]

To be clear, a half full keg and a full keg (with same surface area) will absorb CO2 from the headspace at the same rate. However, the half full keg only needs to absorb half as much CO2 into the beer, so will carbonate in about half the time, as a full keg. An over filled keg will take longer to carb, since once you get above the vertical side wall level, the surface area starts reducing very quickly.

Brew on

I can second this. I recently “packaged” 6 gallons of beer in a 10 gallon keg and burst carbed and shook. the beer was initially overcarbed very quickly and with some degassing at first, hasnt seen gas since. Ive been pouring from residual pressure in the keg and it’s conditioned nicely and worked out. Normally my beers get burst carbed in topped-off 5 gallon kegs and the burst carbing for 24 hrs doesn’t overcarb as much compared to this keg with much more headspace

 

[Homebrew Harry]

I'm glad we got that cleared up !