On April 27, 2014 I harvested yeast from my Dundalk extract kit - “Wyeast 1968 London ESB”. I followed John Palmer’s instructions and ended up with three mason jars each with 1/2 inch little yeast cake sitting at the bottom…
Um, now what? 
How do I figure out how much yeast / how many cells are in there / how should I use it / pitch rate etc?
I was thinking of using it in a simple self-designed extract recipe. I have only brewed 4 times, all N.B. extract kits.
First you need to figure out how many milliliters of yeast you have. Mason jars work well because they have markings on the side. Then use Mr.Malty’s repitching calculator to tell you how much to use in your next beer.
Just some food for thought, do some research on yeast rinsing vs not rinsing. There are a few different schools of thought. I used to rinse all the time, but got away from it and now just collect straight slurry. A lot less fuss and works just as well. Something to think about is all.
I agree with Dobe about the lack of need for yeast rinsing. Check out ‘Woodlandbrew’ s blog. He’s done enough convincing work that indicate that when you rinse you throw out about 1/2 of your viable yeast.
Usually after I’ve harvested yeast I wind up with 3 qt. mason jars. I try to use it within 2 weeks and pitch 1 jar if my OG is less than 1.060, 2 jars if over. If I went beyond two weeks I’d probably do a starter, just to be sure.
Okay, great, thanks!
So… I have my Patersbier extract kit in the primary right now; it is on Wyeast 3787 Trappist that I pitched from a smack pack. I have a Dubbel kit ready next - should I just pour the wort from the Dubbel onto the cake in the bottom of the primary after I siphon out my Patersbier? Is that how it works? I have a smackpack for the Dubbel (Wyeast 1214 Belgian Abbey), but it would be fun to reuse the previous yeast.
Would I just pour the aerated wort right on top? Then shake it up?
You might not need the whole cake for the dubbel, but yes, you’ve got it. Pour onto yeast cake and shake it a bit and you will see crazy fermentation not long after.
