Irish Stout fermentation

[DanInSydney]

Got a stout on the go in 2 glass carboys.

3 weeks fermenting and looked finished - beautiful black colour. But...

Yoday 1 of the carboys started bubbling away like crazy and has gone back to the brown colour it was before turning black.

See left back right above. Any idea whats going on?

 

[Miraculix]

It started to ferment again. You either had a stalled fermentation which somehow solved itself, or you got an infection with a yeast with higher attenuation than your original yeast. What yeast did you use?

 

[OldDogBrewing]

What Miraculix said, maybe it was stalled and got solved by itself or due an environment change (the room temp raised for example) or something got in there and it has been able to grow once the yeast dropped and it's chugging away, what did you fermented in there before that stout?

 

[DanInSydney]

Thanks for the ideas. I used Belgian Ale Yeast #WLP550.

Still bubbling away this morning... looks like it was just a stuck fermentation but weird how the carboy next to it has finished!