cubbies

Recipes 

I have given up on yeast washing and I now use the technique you are describing here. You can read up on my experiment and my results here

alpo

Recipes 

You can use a White Labs vial a lot more than 4 times too. If you do a 3 stage starter with a stir plate, you only need several drops, but it does take a while and you need a stir plate to get a good cell count.

Day 1, add some drops of liquid yeast into 10 ml starter wort(small container.. I use a little glass cup), 3/4" or 1" stir bar
Day 2, add to 500 ml starter wort, step up to larger container, switch to 1.75" or 2" stir bar
Day 3, add 500 ml starter wort
Day 4, crash cool
Day 5, decant and pitch

I have done this a handful of times with great success. I end up with what would have been around 2 full vials worth of yeast. I'm not 100% of the quantity, but it's enough that you'll need a blowoff tube in about 24 hours or else you'll blow out your airlock or lid.

I am not quite sure how long this can be repeated without eventually contaminating the master vial. I try to open it, pour some and close it as quickly as humanly possible.

tedski

Recipes 

This is why its best to have a master culture and a working culture when working with yeast. The master is only ever used to inoculate more working cultures. The working culture is used to step up to starters. This minimizes the chances of contaminating your master culture. If a working culture is contaminated, no big deal. You simply use another working culture or inoculate a new working culture from the master culture.

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"This is grain, which any fool can eat, but for which the Lord intended a more divine means of consumption. Let us give praise to our maker and glory to his bounty by learning about... BEER." - Friar Tuck