Saving yeast?

[liquidlunch]

Question sorry if this is a dumb one but I have never saved my yeast before. 2 weeks ago I made a real big starter for my 1098 and saved some for my next brew. What I did was; transferred my beer to the keg and poured about a half of a mason jar full of yeast and put in fridge. The first week it settled out nicely and I was going to decant it a week later. Well tonight is a week later and the yeast seems to have activated again and was carbonating the jar and the yeast cake from the bottom was now on the top of the jar. I opened the jar and it was pretty carbonated. What did I miss? I though the cold temps would stop any yeast activity?
Thanks

 

[stansoid]

Have you read the post on yeast washing? https://www.homebrewtalk.com/showthread.php?t=41768 that may be helpful for you. You are on the right track, but some pretty easy steps could help you out a bit.

 

[ericbw]

It was a starter? Why did it go in the keg?

 

[kh54s10]

My guess is that the yeast in the jar has an infection.... I would dump it and start over. Nothing should happen in a saved jar of yeast.

 

[liquidlunch]

It was a starter? Why did it go in the keg?

It didn't the beer went in the keg and I poured the yeast from the bottom of the fermenter into a mason jar.