Cold Crash Suckback Issue - Resolved

[mac_1103]

If there is active fermentation at the lower temperature, then the carbonation level will increase much faster than if CO2 was just being absorbed from the headspace.

Interesting. I assume also not a simple calculation?

 

[kohalajohn]

I'll report back on how it goes.

 

[doug293cz]

Interesting. I assume also not a simple calculation?

Anything involving rates usually gets you into dealing with differential equations. Sometimes you can make some simplifications that will allow you to bound the solution space, but getting actual answers is often difficult.

Due to the way CO2 is generated in the fermenting beer, the CO2 is in solution as it is created. Once you have bubbles, the beer is saturated with CO2, and the bubbles form when excess CO2 comes out of solution.

Brew on

 

[kohalajohn]

As promised, photo of the situation post crash.

Yeah, starting the cold crash with a pressurized vessel does the trick.

I ferment under pressure, in cornies, with a spunding valve.

I was at about 10 psi before the crash. After two days at 38f I was down to 5 psi. That big drop in pressure shows me that if you don't start with a pressurized vessel, you'll definitely have to install some system to prevent vacuum suck back.

I should add that I only had 4 gallons of beer in a 5.25 gallon keg, so I had a LOT of headspace with that 10 psi. Less headspace, perhaps more pressure needed. Or second top up halfway through.

Photo attached. The second keg to the right is my serving keg. The fermenting keg has been purging it to get it ready for today's transfer.