I received some slurry from a local brewery about a month ago -- I never washed it and it separated into some nice thick yeast on the bottom and beer above it. It has been in the fridge the entire time since I got it.
Shortly after I brought it home, it formed a new krausen and I couldn't figure out why -- I figured the yeast just weren't done fermenting yet and exposure to oxygen got them started again.
I was going to finally wash it and split it up a bit tonight when I noticed it was back at it and a bunch of yeast were now at the top again, floating in a thick paste.
Anybody have any ideas why this keeps happening? Periodically I'll pop the lid to relieve pressure -- is oxygen getting in and making it reactivate? Any concern with washing and re-using this yeast?