# How much washed harvested yeast is enough?

I washed a fourth generation 1945 Wyeast Neo Brit and would like to use it in a Barley Wine for Christmas 2012 (If the Mayans are wrong). In the pint jelly jar, washed I have 4 inches of beer a 1/4 inch of clean off white yeast (I’m assuming) and 3/4 inch of trub. I will be making a 1.5 ltr. starter on a stir plate. How does one know if this is enough viable yeast until you go through the process and crash and burn?

Calc the volume and viability of the yeast to determine how many viable cells you have. Then go to Mr. Malty and enter that info into the pitching calculator to determine what size starter you need.

∏*(Radius cm²)(Height cm)(Cells per ML)*(Viability)= Viable Yeast Cells

Cells per ML is variable, typically I use 3.5 billion per ML in the calc.

To find viability I use Mr. Malty and enter the original pitching date into the production date field.

Example:

Mason jar with a radius of 2cm, a yeast depth of 1.2cm, and an original pitching date of 10/17/2011
Mr. Malty calcs yeast from 10/17/2011 @ 40% viability

∏*(2²) = 12.56
12.561.2 = 15.08
15.08
3.5 = 52.78
52.78*0.4 = 21.11 billion viable yeast cells

I often wondered the same thing. My mason jars have ml label on the side of the jar. I like to get around 100ml of just healthy yeast (no trub) and then make a starter. Not sure why I use that amount. It just seems right. It sounds like you don’t have enough though. 1/4" isn’t very much. That’s a good starting point, but I’d make a nice big starter.

I’ve often wondered how Mr.Malty’s repitching calculator works. I know it’s looking at slurry, but what is slurry? Is that the entire yeast cake un-rinsed? It can’t be rinsed yeast, can it? I made a starter last night for an average OG Honey Weizen 1.054. The yeast was collected in December from a beer that was brewed in November. Mr. Malty told me I’d need something like 800ml of yeast to repitch. That’s insane! That’s a sh*t ton of yeast. I made a 1500ml starter from 200ml of clean, white, rinsed yeast.

Anyway… I hope someone can give some insight on this question because I’m curious.

200 ml of clean white yeast would be around 700 billion cells, assuming 50% viability your looking at 350 billion viable cells.

Using that yeast to make 1500ml simple starter would yield about 370 billion cells

[quote=“gregscsu”]200 ml of clean white yeast would be around 700 billion cells, assuming 50% viability your looking at 350 billion viable cells.

Using that yeast to make 1500ml simple starter would yield about 370 billion cells[/quote]

I think I’m confused on how to use Mr.Malty’s repitching calculator then. I entered:

Ale
1.054 OG
5.00 gallons
Use date 11/16/2011 (date I pitched the original yeast)
Viability 13%

# ml of yeast needed 477 (this after adjusting the concentration to 3.5 like you suggested)

So, why is the viability coming up with 13% and you’re saying 50%? Not doubting you at all. I actually hope your numbers are right. Because if that’s the case, I really didn’t even need to make a starter. I could have just pitched the yeast, but whatever. That doesn’t bother me. I am over pitching I guess, but I must be figuring something wrong in my numbers.

Mr. Malty calcs the viabiltiy on yeast slurry very low. The calculator assumes that you just scooped a cup of slurry straight from bottom of the fermenter and put it in a jar. No rinsing, and no beer layer on top.

I find that with my practices I get much better viability then what the slurry calculator predicts.

I figured from your original post that you have very good sanitation and washing procedures, which would increase the viabiltiy over what the calculator suggests.

That’s kinda what I thought Mr.Malty was doing… assuming unwashed yeast mixed with trub. So to figure your calculations you use 100ml of clean, white yeast is about 350B yeast cells? So if I use Mr.Malty to tell me how many cells I need, I can just use those numbers to figure if I have enough? And how do you calculate viability? Assuming rinsed, clean white yeast, stored under beer in a mason jar in a fridge. I assume you have some rule of thumb as to every month you lose so much viability?

One more question, how do you figure out starter sizes and how much yeast you’re actually growing?

Thanks for all your input! It’s a huge help.

Thanks for all your feedback. If you hear a pop from SE Wisconsin that’s my head exploding. I find the process so dang interesting This batch of 1945 Neo Brit. has done a remarkable job on 4 batches and it will be hard to say good bye.

I’ve gotten so much use out of my Neo Brit too! This yeast stuff interest me so much that I think I’m going to get a hemocytometer and start counting viability of my starters made from slurry.
:cheers: