[Andor]

With pure top cropped yeast what cell density should I assume? I'm looking for a rough guess if anyone has one. The difference between assuming 1B cells per ml and 4.5 cells per ml is a pretty big difference.

[Andor]

Yes 100 views !

[Stevie]

Sorry you're not getting an answer. I harvest slurry post ferm, so I have no idea.

[69franx]

I also have not top cropped so no help here

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[hopfenundmalz]

This may or may not have your answer.
http://braukaiser.com/blog/blog/2012/08/24/yeast-pitching-by-weight/

[Phil_M]

I can only answer with another question: What is the purpose behind needing to know the cell count?

From a starter perspective, provided your sanitary practices are up to snuff, you'll get more than enough yeast to "seed" a normal starter.

Keep in mind though, that if you're looking to pitch from one beer straight into another new beer, those high krausen yeast are VERY active, far more active than yeast from a stir plate starter would be. You'd need less yeast than you think, as they're already primed for replication.

https://www.experimentalbrew.com/blogs/saccharomyces/yeast-cultures-are-nuclear-weapons

[ynotbrusum]

That's why I typically see a repitch from top cropping in the suggested 50 to 150 ml range...I don't think exact cell counts are a concern - it's okay just to be in the ball park, since most of us don't have hemocytometers to do a proper count!  Best of luck with the top cropping - I'm sure it will work out fine.

[Andor]

I can only answer with another question: What is the purpose behind needing to know the cell count?

From a starter perspective, provided your sanitary practices are up to snuff, you'll get more than enough yeast to "seed" a normal starter.

Keep in mind though, that if you're looking to pitch from one beer straight into another new beer, those high krausen yeast are VERY active, far more active than yeast from a stir plate starter would be. You'd need less yeast than you think, as they're already primed for replication.

https://www.experimentalbrew.com/blogs/saccharomyces/yeast-cultures-are-nuclear-weapons

I had 100 ml of settled yeast top cropped yeast. Assiming the low end 1b cells per ml the pitch rate would be 0.39m/ml/p for the beer I was making. I'd want a starter.

But at 4.5b cells per ml, I read somewhere this is the high end for density it'd be 1.74m/ml/p. Which would be more than I'd want for the bitter I was doing. I'd

I know these numbers are like ibus probably even worse. I'll never know what's actually there. I'm just looking to establish a standard practice with a best guess for cell density

[a10t2]

I think you'd be doing well to get even 2 billion cells per mL from a top crop. That's about the most I've seen from the bottom of a conical, and the top crop is going to have a lot of CO2 entrained. Probably better to go by mass just to be consistent.

If you could de-gas the crop and then cold crash it for a few days you could get a decent estimate of the starting density. At that point the slurry should have packed down to 3-4 billion/mL.

[Saccharomyces]

If you could de-gas the crop and then cold crash it for a few days you could get a decent estimate of the starting density. At that point the slurry should have packed down to 3-4 billion/mL.

Three billion cells per milliliter in settled clean top-cropped slurry is about right. 

[mirko_legisa]

I ve read a lot about this and the only conlcusion that I have is that it is totally dependant on the strain that you re using. If you find some good data on internet about THIS particular strain, you can rely on that, otherwise you ll have to test it yourself. If you have a microscope it will be better, otherwise you should aproximate the counting from a slurry and try it in your batch, I mean, read about some similiar strain slurry-counting and try. Under-pitching or over-pitching results on typical descriptors that you will find in your final beer.
cheers