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You are here: Home --> Forum Home --> Brewing Forum --> Brewing Discussion --> Yeast Calculator Overbuild Question

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Snoballz
Cordova, TN
12 Posts


I usually add an extra 500ml to my starters for harvesting, but I wanted to try the calculator on this site. Apparently I don't understand how to use the overbuild function.

If my first step is 1L and my second step is 1L, how can the harvest amount and pitch amounts equal only 1L? Even if I crash and decant between steps, there's still more than one liter in the end. 





Posted 34 days ago.

homebrewdad
Charter Member
Birmingham, AL
2480 Posts


Okay, so let's figure this out.

What are your inputs?  I.e. batch size, OG, yeast date, etc.  What size flask do you have? 

I'll run it myself and see if we can't find the issue.





Posted 34 days ago.

Snoballz
Cordova, TN
12 Posts


Batch Size = 5.5 gal
OG = 1.04
Overbuild = 100b

Initial Cells = 100b
Prod Date = harvested on 8/21/2014
Flask Size = 2L

The calculator suggests two 1L steps of 1.037G.

Here's where I'm confused. The calculator suggests that I pitch 0.658L and harvest 0.342L for a total of 1L. If I'm using two 1L steps, shouldn't there be more than 1L at the end of the second step?





Posted 34 days ago.

brewcrewkevin
Charter Member
Appleton, WI
66 Posts


The calculator assumes you are cold crashing in-between. And you end up with a 1 liter starter. Sure, it would probably be a bit more than that since your slurry is a certain volume, but that would be almost impossible to capture.

Basically that is saying you will need 65.8% of your starter. I would round that to 2/3 and use 2/3 of your starter. Save the other 1/3.

It's never going to be exact. But I think it gives you a really good idea of how many cells you have.




Posted 34 days ago.

homebrewdad
Charter Member
Birmingham, AL
2480 Posts


Yep, Kevin nails it.  It's assuming you are cold crashing after each step and decanting the liquid, then pitching that slurry into a new liter of starter.  At the end, you're going to be left with roughly 1 liter, not two.

Note that if your flask is big enough, you can just add another liter of wort at the second step and call it a day - but then, you'd need to apply those  same percentages to harvesting.  Which means you need a bigger jar or whatever to save your slurry.

I always cold crash and decant what I save, which I then store in soda blank vials (same thing White Labs ships yeast in).





Posted 34 days ago.

Snoballz
Cordova, TN
12 Posts


I was thinking in volumes not percentages. It makes perfect sense now. Thanks!

The wife would probably be much happier if I started using soda blanks instead of 8oz mason jars.






Posted 34 days ago.

homebrewdad
Charter Member
Birmingham, AL
2480 Posts


Nice collection! 

But yeah, soda blanks are the way to go (IMO).  They easily contain 100B+ cells, plenty for a starter.



Posted 34 days ago.

brewcrewkevin
Charter Member
Appleton, WI
66 Posts


Just to be clear, Snoballz, the calculator does it in volumes. But it's a fairly simple calculation based off percentages and whatnot.



Posted 34 days ago.

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