[Pi]

What I've been doing is swirling the yeast cake with about an inch or so of the beer sitting on top in the carboy. then pour about .75l. into an Erlenmeyer flask. when I'm ready to make a starter i pour off the beer and put fresh wort on the cake. I've read about washing the yeast in distilled water. So which part am I supposed to use, the cake or the beer?

[tomsawyer]

The cake is the yeast.  Cold crash to get it all to drop, then decant off the beer and add some boiled/cooled water.  The yeast settles on top of the trub for the most part, so you can carefully swirl to get some of the top stuff off without getting the trub suspended.

I don't usually wash my yeast and have never had problems.  I don't leave as much beer as you, in fact I'll decant all the beer I can off the cake then use a clean ladle to fill a 1-cup jar and save that in the fridge for up to several months.  I can use it direct for the firt month, or make a starter later.

[Malticulous]

I rack as much beer as I can, re-sanitize the lip of the fermenter and try pour it all in to a quart jar. If I don't have much trub it fits. There I probably have 700-800 billion or more cells. They die fast though. I like to use it within a week.

I've read that ideally you want cell count to multiply 3-5 times during fermentation, so i know depending on pitch rate I have enough for three to five batches if I use it right away. It's not good to repitch from batches pitched higher than that because it has too many old cells. I think this is one reason why others have had problems repitiching lagers.

I like to start out with a low gravity batch and harvest it for a big beer and another normal one. The normal gravity batch will keep my yeast healthy and alive for more batches latter. This way I get 5-15 batches out of one pack of yeast. Most people don't brew as often as me though. They are probably better off storing it in the fridge and making starters later.

[tomsawyer]

Malti why do you think the yeast dies so quickly?  How is our cake that much different than Chris White's?  I do brew pretty often but I carry a half dozen yeasts so I normally seed a starter and let it grow up.  I agree that letting the yeas multiply a couple of gnerations in a starter probably gives a youthful pitch.

[Malticulous]

The biggest thing is I no longer have any clue to how much viable yeast I have or their vitality and I start to worry about a contamination taking hold. A starter helps with most of that, so could a microscope and a hemocytometer. If I get my five or more batches and it sits in the fridge long I think it's worth spending  money on a new culture. I'd like to have a lab but I also think what the yeast companies do is worth the price.

[tomsawyer]

I agree with that, getting four or five batches brings the cost per batch into the range of a buck and that makes it worth having the labs ranch it for you.

[Malticulous]

I think when you harvest you want a good cross section of the population to continue to get similar fermentation characteristics. Long storage is going to select a part of the population.

I've had few issues top cropping too. Once I cropped some WLP320 and the beer dropped perfectly clear. The esters are there but I sure did not expect that to happen. I've also gotten low attenuation form top cropped American ale yeast. Top cropping is not as easy as I thought.

[sharg54]

I haven't tried top cropping but have done a good deal of Yeast washing. It works out quite well and I have been able to go 4 generations down without a problem using White labs pilsner 800 and there Irish ale 004.They say you can do 6 but why push your luck if you don't have to. 
Its not all that hard and if you want to read up on it this is a fairly good site on the subject. http://www.brewersfriend.com/2010/01/30/yeast-washing-101/
I don't think you get as much yeast this way but what you get is healthy and I have stored it up to 3 months without any bad effects. I think the less junk you take with the yeast the longer it will last in storage but that is just MHO. The biggest thing is keeping everything clean and sanitized so you don't contaminate.   I just use it to make my starters and it works out just fine and being as I use a starter on everything I brew there are no real added steps. Just plenty of yeast on hand and what with being able to pull off 6 bottles each time I do wash it turns into quite a savings at 8 bucks a bottle at the brew shop.   

[nateo]

Malti- That's interesting about top cropping. I've always read that's the best way to harvest yeast.

I used to do quite a bit of yeast harvesting. Sometimes I'd have trouble separating the yeast from the trub when pouring into jars. I wonder if something like this:http://www.ebay.com/itm/Norpro-2-Cup-Gravy-Fat-Separator-/280808993862#vi-content would make it easier to pour out the trub and keep more of the yeast?

In White and Zainasheff's book on yeast they have a good bit about DIY yeast labs. I've though about getting something like that set up but dry yeast is just too darn convenient.

[phunhog]

Lately I have been making stepped up yeast starters for the sole purpose of harvesting yeast.  I usually start with one WL vial in a 1L starter, crash, and decant into a 2 L starter. I crash that one and pour the remaining yeast into 4-5 sanitized WL vials. My thought behind this is that it easier to keep everything sanitary just dealing with flasks and vials, the staters don't stress the yeast, very little trub/hop particles, and it gives me something to do when all my fermentors are full