I've got some 2 month old washed yeast in a 250mL mason jar in the fridge. It's about a 3/4" layer. I'm trying to figure out how much starter wort I need to make to get a proper pitch rate for a 5.25 gallon 1.050 beer. I've consulted Mr. Malty's slurry calculator but I'm still confused. So...
1. When making a starter in this case is it to get the yeast waked up before I pitch in my beer wort as well as to check viability?
2. If so, what is a good quantity? 1 litre, 1.5 litre?
I make starters with washed yeast all the time. Since you are making a normal gravity beer, 1.050 i would go with around 750ml of water, boiled with 0.5 cup of DME. I have always had good luck with that sized starter on beers around that gravity.
Making a starter ensures that you have live, healthy yeast, and it also allows them reproduce so you can have more yeast to pitch and get a good fast fermentation.
If your washed yeast is several months old you have for surely lost some viability. If your yeast is 75% viable you will need between one half and one liter of yeast depending on how thick your slurry is. To get that much yeast you are going to need to make a huge starter and step it up several times. If the yeast if only 50% viable then you will need even more. I'm not sure maybe I'm wrong. I've never used washed yeast.
It seems like this would be lots easier if you just got a packet of Nottingham or S-05...
From what I remember about the podcast, if he is pitching from a slurry, he doesn't use a starter to build up the yeast. Instead he calculates how much yeast slurry to pitch to give a cell count equivalent to the needed starter.