Carboy Question

If I want to rack a beer on top on a yeast cake in my carboy, obviously I won't be cleaning out the carboy... so...

Is that ring of leftover krausen that sticks to the walls of the carboy bad for the new beer? It's not full of bad bacteria or anything is it?

5gB

If you've kept the entire thing sealed up during the whole fermentation, everything in the carboy is good stuff. That ring at the top is generally composed partially of hops, and it is extremely bitter, but if you go through an entire second fermentation, everything will settle back out, either at the top in a new ring, or settled into the trub at the bottom. Just keep everything sanitary and you'll be fine. I'm going to be doing the same thing in a week or so.

Remember to pitch a darker (colored) beer on top of of the cake from a lighter one. Don't try to pitch a lighter beer onto, say, a brown or porter cake.

I would also think that literally pitching "ON" on the cake isn't necessary. Once you rack your first beer off, I suppose you could drop some sanitized water in, swirl a bit and then pour it into a sanitized "holding" bucket while you clean up your primary. There are so many viable yeast cells in that cake that you won't even need all of it. Once you go this far though, you might as well go for actual yeast washing where you extract mostly yeast while leaving behind all trub.