Does Wort Have a Positive Vapor Pressure?

[Hwk-I-St8]

I'm really curious about what's happening with the BB Porter I'm aging in a keg. Fermentation is long complete, SG is stable, yet it builds up pressure daily. This has been going on for over a month where everyday there's about 2-3 psi pressure build up. I bleed it off, the next day it's back up.

What causes this?

Samples are great BTW, nothing odd going on that I can detect. Just curious what's happening.

 

[Turkeyshot]

I'm really curious about what's happening with the BB Porter I'm aging in a keg. Fermentation is long complete, SG is stable, yet it builds up pressure daily. This has been going on for over a month where everyday there's about 2-3 psi pressure build up. I bleed it off, the next day it's back up.

What causes this?

Samples are great BTW, nothing odd going on that I can detect. Just curious what's happening.

Seems normal, there is carbonation in your beer already. Plus if it is stored anywhere slightly warm it would build up a little pressure just from the temperature going up.

 

[dyqik]

It's probably outgassing CO2 put into solution during the ferment. That's because the CO2/Carbonic acid in solution exists in an equilibrium, with a slow rate of conversion between the CO2 and the two forms of carbonic acid. As CO2 outgasses from the wort, more carbonic acid slowly converts to CO2 in solution to bring the wort back into equilibrium, and thus more CO2 can outgas.

2-3 PSI sounds a bit high for a month of outgassing (based on no experience or data whatsoever, so I'm entirely guessing here), but is the temperature rising at all?

 

[Hwk-I-St8]

Temp should be fairly stable. It's in my basement. It may fluctuate a couple degrees, but it's not steadily rising.

I'm not worried about this, just curious what's happening. The beer samples are outstanding.