Is this enough washed US05 for a 5 gal batch?

[OopsMD]

I plan on making a 1.040 starter 24 hours ahead of time, pitching into a 1.045-1.050 wort. Not sure how much is needed to make a good starter.

 

[brew_darrymore]

This looks fine! Decant, shake and pitch into your 1.040 starter. You may want to overbuild your starter to save some yeast for future batches.

 

[Jag75]

Just curious, but when you guys save and wash yeast do you know how many cells you have as you go ? Do you send in samples to get an accurate count ? I've never been interested in yeast collecting but its starting to peak my interest.

 

[OopsMD]

Just curious, but when you guys save and wash yeast do you know how many cells you have as you go ? Do you send in samples to get an accurate count ? I've never been interested in yeast collecting but its starting to peak my interest.

I doubt anyone would ever do that, since the idea of washing yeast is primarily to save money. I think they make tools that you can measure cell count with though.

 

[IslandLizard]

Just curious, but when you guys save and wash yeast do you know how many cells you have as you go ?

After properly rinsing* yeast and looking that white and clean, estimate around 2.4 billion cells per ml of settled slurry (per Mr.Malty/Jamil Zainasheff). It could be somewhat higher or lower, depending on how much non-yeast material it contains.

So for that ~2.5" (=6.25 cm) diameter jar, the settled slurry has an (estimated) volume (V) of:

V = π * r^2 * h = 3.14 * (3.13)^2 * .5 ml = ~15 ml​

15ml * 2.4 billion cells/ml = 36 billion cells.

I'd put that into a yeast calc for age and starter build up.
BrewUnited's Yeast Calculator

* Yeast "washing" is a whole different method, involving Chlorine Dioxide.

I plan on making a 1.040 starter 24 hours ahead of time

Depending on how old the slurry is, I'd probably give it a couple days longer for some extra growth. When it's done, it should get thick and creamy looking.
If you want to brew this weekend then pitch the whole starter, without cold crashing, and perhaps save some out for next time.

 

[Jag75]

Thanks @IslandLizard for that detailed post !

 

[VikeMan]

* Yeast "washing" is a whole different method, involving Chlorine Dioxide.

And there's also yeast acid washing, which is also different from rinsing. Here's how I usually feel when trying to get folks to stop referring to rinsing as washing: