Yeast Cake Reuse

[stephenlcurtis]

I recently finished brewing 5 gallons of American Pale Ale. This coming weekend I want to brew a 5 gallon Pliny clone. I poured the yeast cake from the APA into 3 mason jars and stored it in the fridge, I figure I will put it at the bottom of the bucket when I pour in the cooled wart to ferment the Pliny this weekend. My question is if there is any methodology to how to determine how much of the previous cake to use on the next batch. In the shows and the books when it talks about pitching yeast and starters it is always very specific. But then the advice in high gravity shows is just "pitch onto a yeast cake". Is there anything more to it than that?

[Bad Goat Brewing]

Jamil has a repitching from slurry tool on mrmalty.

http://www.mrmalty.com/calc/calc.html

[Klickitat Jim]

In my opinion, if you have time, the best method is to make a proper starter using about 90ml of the old yeast. Then you are brewing with fresh healthy babies

[stephenlcurtis]

Thank you both, this is exactly what I was looking for!

[stephenlcurtis]

Wait, how do I know what my yeast concentration and non-yeast percentage is to use Jamil's calculator?

[Klickitat Jim]

Wait, how do I know what my yeast concentration and non-yeast percentage is to use Jamil's calculator?

Precisely!

I repitched way too much for a while till it dawned on me. So what I do is leave a half inch or so of beer on the cake when I rack. That gets swirled up and dumped into a half gallon mason jar. If I'm repitching soon I agitate the jar to get a nice homogenis slurry and guess that it's about 2 billion per mil. So a 1.050-60 gets about 2/3rds of a cup. But only if repitching so soon there's no time to make a starter. Otherwise I swirl it up and pitch 80-90ml into a 1500-2000ml starter.

Unless you count cells it's hard to say what you've got. But it's safe to say that if it's as thick as yogurt you're pitching too much unless you somehow adjust for that.