MagicMatt
Brewmathemagician
Hi all,
I have experienced this situation several times over the years and just can't wrap my head around what's happening, so figured I'd reach out to see if anyone can shed some light for me. We all know that when you take a cold, carbed keg out of the keezer and let it warm up that the pressure will rise as the temp rises and CO2 comes out of solution. My question is basically how long it should take for a warm keg's pressure to get back down to serving pressure once the temperature is brought back down? I would think this should happen over a week or so, but in my experience that never seems to be the case.
My current situation:
I had 2 fully carbed kegs in my keezer at 36°F. Both had been on constant CO2 pressure for 8 weeks but carbed to different levels: Keg A at 11psi (~2.6vol), Keg B at 5psi (~2.0vol). A couple of months ago I had to re-purpose my keezer as a freezer, so I disconnected the gas and pulled the kegs and let them sit at room temp (72°F-ish). A week later I checked the pressure on the kegs and they were at 40psi and 24psi for Kegs A/B respectively, which checks out for what should happen according to the carbonation charts.
Fast forward to last weekend and I had my keezer back, so I put the kegs back in. I measured the pressure at this time and it had not changed (40psi/24psi), which shows there was no refermentation or anything crazy - carbonation volumes remains unchanged, as one would expect since it is a sealed container. So the kegs have been at 36°F now for 8 days, yet the pressure has not gone back to what it should be for the temp it is at. Currently they are sitting at 30psi and 19psi.
Why is it taking so long to equilibriate? Sometimes I burst carb my kegs at 40psi for 26 hours and it's at roughly 2.5 vols, so why is it taking so long for the 40psi head space to go down? I know if I have a fully carbed keg, say 11psi @ 36°F, and I apply a 40psi CO2 charge to it, let the head space reach 40psi, and then disconnect the gas, that the pressure will come back down to 11-12psi pretty quickly, within a few hours for sure. I feel like I have essentially the same situation right now (sealed keg, no gas attached, head space at 40psi), and yet it's been a week and it's still only at 30psi.
What gives?
Thanks!
P.S. I debated putting this in the Brew Science sub-forum because I figure there's a formula for CO2 absorption out there with variables for volume, headspace, temp, applied pressure, etc, that should be able to tell me how long it will take, but I'm having trouble finding one.
I have experienced this situation several times over the years and just can't wrap my head around what's happening, so figured I'd reach out to see if anyone can shed some light for me. We all know that when you take a cold, carbed keg out of the keezer and let it warm up that the pressure will rise as the temp rises and CO2 comes out of solution. My question is basically how long it should take for a warm keg's pressure to get back down to serving pressure once the temperature is brought back down? I would think this should happen over a week or so, but in my experience that never seems to be the case.
My current situation:
I had 2 fully carbed kegs in my keezer at 36°F. Both had been on constant CO2 pressure for 8 weeks but carbed to different levels: Keg A at 11psi (~2.6vol), Keg B at 5psi (~2.0vol). A couple of months ago I had to re-purpose my keezer as a freezer, so I disconnected the gas and pulled the kegs and let them sit at room temp (72°F-ish). A week later I checked the pressure on the kegs and they were at 40psi and 24psi for Kegs A/B respectively, which checks out for what should happen according to the carbonation charts.
Fast forward to last weekend and I had my keezer back, so I put the kegs back in. I measured the pressure at this time and it had not changed (40psi/24psi), which shows there was no refermentation or anything crazy - carbonation volumes remains unchanged, as one would expect since it is a sealed container. So the kegs have been at 36°F now for 8 days, yet the pressure has not gone back to what it should be for the temp it is at. Currently they are sitting at 30psi and 19psi.
Why is it taking so long to equilibriate? Sometimes I burst carb my kegs at 40psi for 26 hours and it's at roughly 2.5 vols, so why is it taking so long for the 40psi head space to go down? I know if I have a fully carbed keg, say 11psi @ 36°F, and I apply a 40psi CO2 charge to it, let the head space reach 40psi, and then disconnect the gas, that the pressure will come back down to 11-12psi pretty quickly, within a few hours for sure. I feel like I have essentially the same situation right now (sealed keg, no gas attached, head space at 40psi), and yet it's been a week and it's still only at 30psi.
What gives?
Thanks!
P.S. I debated putting this in the Brew Science sub-forum because I figure there's a formula for CO2 absorption out there with variables for volume, headspace, temp, applied pressure, etc, that should be able to tell me how long it will take, but I'm having trouble finding one.
