1 gallon Square keg

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RJjtown

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I recently purchased a 1 gallon Square keg. I am naturally carbonating a cream ale. I racked the beer to the keg, added my carbing drops and sealed the keg with the mini regulator attached. After about a week the gauge is showing about 15psi. I plan to put the keg into the fridge for about a week and then bleed off the pressure, attach the co2 cartridge and set it to 8-10 psi and hopefully serve some beer. Does all this sound like a reasonable plan? Thanks!
 

Deadalus

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If you correctly calculated the number of carbing drops for the desired volumes of CO2, should be okay. You would want to let the keg sit at room temperature until the drops finished which I believe is about the same for bottle conditioning. I've never used the drops but I would just suggest 3 weeks minimum. You want them to finish up then let the beer clear but it's in the keg so you can't check that. You can't pour it at 15 psi without it foaming. You wouldn't want to bleed it before knowing it was done. Once the pressure stabilizes over a few days, it's not fermenting anymore just be aware that the pressure can change with room temperature change as well as you may not see small pressure changes depending on the gradation of the gauge. Then give it time to clear.

If I am using the ideal gas law properly P1/T1=P2/T2. I'm also thinking I don't need to convert to metric since it would cancel out on both sides. So if at room temperature 72F and if your fridge was set at 40F, and your drops were done you'd have 15/72=P2/40 and P2 =8.33. Now if you force carbed at 8.3 psi at 40F the you would be at slightly more than 2.11 volumes of CO2, between 2.11 and 2.20. That's a little under the low end for carbonation I see listed for cream ale 2.3-2.8 volumes. But what's room temperature for you? You may still have some carbonation building as well, it's only been a week. I think you'll be where you want to be in at least another week plus a week to 10 days to clear.

I'm not sure at all about the 8-10 psi because you might have the tap attached right to it without the usual 5' beer line. Was that the suggested level in any instructions for the regulator and/or tap that is attached?

You're really going to want to get a 5# CO2cylinder ASAP to avoid that wait!
 
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RJjtown

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The carbonation drops I am confident will provide the levels that I need. It was mostly the other factors I wasn't so sure of. The 8-10 was the suggested serving pressure. I appreciate greatly your expansive suggestions regarding the rest of the process. I will keep them in mind. Thanks so much!
 

maryc27182

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If I am using the ideal gas law properly P1/T1=P2/T2. I'm also thinking I don't need to convert to metric since it would cancel out on both sides. So if at room temperature 72F and if your fridge was set at 40F, and your drops were done you'd have 15/72=P2/40 and P2 =8.33. Now if you force carbed at 8.3 psi at 40F the you would be at slightly more than 2.11 volumes of CO2, between 2.11 and 2.20.

The temperature in the ideal gas law needs to be absolute, which means-- if we stay in American Engineering Units--that we have to add 459.67 to the temperature in degrees F. (The addition process means the unit change doesn't cancel out for the temps, but you are totally correct that we can use mixed units everywhere else.)

I bottle, and have never kegged, so I'm going to ask a question: are keg pressures measured in absolute, or in gauge? Because the pressure in the ideal gas law also must be in absolute (and that's also one of those addition processes, which will change things.)

Mary (retired engineering professor who doesn't know much about kegging, but who has marked off points from students' exams for not-using absolute temperatures and pressures in equations of state)
 

Deadalus

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The temperature in the ideal gas law needs to be absolute, which means-- if we stay in American Engineering Units--that we have to add 459.67 to the temperature in degrees F. (The addition process means the unit change doesn't cancel out for the temps, but you are totally correct that we can use mixed units everywhere else.)

I bottle, and have never kegged, so I'm going to ask a question: are keg pressures measured in absolute, or in gauge? Because the pressure in the ideal gas law also must be in absolute (and that's also one of those addition processes, which will change things.)

Mary (retired engineering professor who doesn't know much about kegging, but who has marked off points from students' exams for not-using absolute temperatures and pressures in equations of state)
Thanks Mary! I should have run through the temperature conversion, I wasn't thinking about the sum. I suppose we might have used gauges in Chem lab but that was ages ago. I did get an A in Inorganic Chemistry but it's not showing here!

They would have to be gauge pressure on the beverage regulators as the gauge starts at 0 and reads zero when first attached. Double checking I ran into a mention at Beverage Factory where they offer a suggestion for adjusting for one's elevation since the carbonation charts are calculated for sea level and atmospheric vs gauge pressures are mentioned there.

So then (this assumes sea level for the absolute pressure correction)
(Atmospheric pressure + Gauge pressure room)/( room temp +459.67)=(Atmospheric pressure + Gauge pressure fridge)/(fridge temp+459.67)
(14.696 +15)/(459.67+72)=(14.696 +X)/(459.67+40)
29.696/531.72=X/499.67
X=27.91(which is absolute pressure) so fridge gauge pressure 27.91-14.696=13.21 psi. That would be slightly more than 2.56 volumes in the fridge if the yeast were done with the carbonation tabs and the CO2 had equalized. (Also assumes sea level) That's in the cream ale range if the fermentation and absorption are finished.

Please don't dock me for the significant figures and not completely including the units!
 

maryc27182

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Oh cool, thanks for the information and the new calculation! I know very little about kegging, even less about the chemical aspects of equilibrium carbonation in a keg, and have been a bit timid about posting in this forum, where so many are experts. (Long-time lurker, first-time poster here.)

The gauge pressure of the room should be assumed as zero, though. (This is exactly the kind of thing I'd do on an exam hahaha, give students part gauge measurements, and part absolute measurements.)

As for sig figs, I was not a chemical engineer, so I'm pretty heretical when it comes to sig figs. (You were smart to realize at the ratio stage that the other mixed units would cancel. Sometimes, in lecture, I'd use mixed units just to freak the students out.)

RJjtown: I'm following this with interest, since I've tried using 1 gallon polypins before, but found I couldn't get through the gallon of pseudo cask beer quickly enough.
 
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