starters from yeast cakes

when making a starter from a yeast cake, i understand that you need to "wash" the yeast to remove trub and dead cells.

but how do you know how much of the cake to rescue? how much is too much? should you "wash" the entire cake from a previous 5 gallon batch? or will that be too much yeast for one additional batch?

and how do you measure yeast cake? by weight -- i'm assuming -- instead of volume?

or am i overthinking this? maybe i should just take a bunch of yeast cake, wash it, store it, and use it again.

ive been lazy before and just swirled the cake around in the carboy to get the yeast into suspension,and then dumped a little bit into my starter flask. it took off in just a couple hours.

One cup of slurry is adequite, and won't have enough trub to bother the 5 gals of brew. Last time I pitched on a live cake, I swirled it around and dumped most of it out. It was my only experience with needing to clean the ceiling.

I would'nt even mess with it. If your brewing then wait and rack off beer when the new wort is cooled and ready to go on. Then just pitch the new beer on top of cake and shake the hell out of it.

I used the yeast cake from my doppelbock to brew a helles the other day. I did wash the yeast first, but only because there was lots of chocolate malt smell in the doppelbock yeast cake, and I didn't want it to taint my Helles. If things were reversed, and I was doing the helles then the doppelbock, I'd just rack the DB wort right on top of the helles cake, and watch the fun begin.

Check out this thread. I posted some pics of the "washing" process there.