Bottle Caps 'bubbling' before capping?

[FrozenWaves]

Hi Guys,

Last night I pulled the fermenter out of the fridge (set to 20 deg) and placed it on the bench while having dinner to let it settle. Room temp was about 22-23 deg.

FG had remained constant for over a week at 1.014 with basically no airlock activity.

A few mins into dinner I noticed the airlock started to bubble every few mins (I put this down to the brew slightly warming and yeast stirred back to life after fermenter being moved)

When I bottle I generally add priming sugar, then fill the bottles and then rest the sanitized cap on top each bottle but dont actually 'cap' them until all the bottles have been filled.

During the bottling, I noticed the rested caps were slowly 'bubbling' like an airlock which I have never seen before. Should I be concerned about bottle explosions? The FG was constant so dont think it was still fermenting. Has anyone else seen this before? Cause for concern?

Cheers

[Peter Church]

Suspect it is CO2 coming out of solution, had the beer reached equilbrium at 20 degrees? I expect that the beer would be super saturated in CO2 after the rise in temp and any disturbance would see CO2 being released, suspect if you poured a glass you would see some CO2/head activity

I see this happen when bottling, yeast cake starts to bubble slowly when the fermenter gets towards empty, less pressure from the beer over the yeast cake as it is drawn off resulting in the CO2 in the yeast cake being driven off.

[FrozenWaves]

Cheers Peter, that has put my mind at ease. Hopefully no explosions...

Yes it had been at 20 deg for 10 days, I measured FG 4 days previous and there was no change when I re-measured last night.

[cjmc]

I get it too, more noticeable when I've dunked the caps in starsan 

I think its a good thing as CO2 pushes out Oxygen leading to longer shelf life and fresher beer. :)