How do I know when I have enough yeast to pitch?

[Dale Owen]

I decided to mess around and harvest yeast from a bottle. I've been feeding it Fast Pitch, building it up in steps. I was pleasantly surprised to discover that the wort I had made started fermenting too. Obviously I didn't sanitize the growler I stored the wort in well enough. Now I have two starters that I've been building up.

My intention is to make a 5 gallon extract batch. I want to use the yeasts I've grown to make two 1 gallon batches. I'll use whatever yeast comes with the kit on the remaining 3 gallons.

Among the myriad other things I've been learning/figuring out, I realize I'll probably need to know how much yeast I have and how much to pitch to those 1 gallon batches. If the above has not made it clear that I am not following the scientific method, let me just clarify that responses that reference pitch rate calculators, etc, probably will hip me to how much I really need to learn, but in the moment will not be something I'm gonna master before my crazed obsession with seeing what these yeast strains will do forces me to fly by the seat of my pants.

 

[cswis86]

How much volume would you say you have so far? If you have a cup or two of fermented wort that should be plenty for a 1 gallon batch. Do you have a noticeable layer of yeast on the bottom of your starter? I get roughly a 1/4" layer of yeast at the bottom of a 1L flask and that's plenty for me to ferment a 5 gallon batch.

 

[Dale Owen]

I've stepped them up to 2L batches of wort twice. After the first batch settled out, I took most of the beer off and started them up again with fresh wort. One is in a 2L flask, the other is in a 1 gal carboy. I would say the one in the 2L flask is probably 1/4 inch or so. That's the one from the bottle. It seems like the less hearty of the 2. The one I have in the 1 gallon carboy is more like 1/2 inch ring of yeast. It's hard to tell for certain, as I've been swirling them pretty vigorously (no stir plate). I figure after this round settles, I'll probably pour off most of the beer again and move what I've got to sterilized canning jars until I'm ready to brew. I'm assuming that I have plenty for 1 gallon batches. Just trying to hazard a guess about how much is too much vs not enough.

 

[cswis86]

Ok, so if you pour off most of the beer I would use about a tablespoon of the concentrated yeast slurry per gallon of wort. That works out to about a 1/4 cup of slurry for a 5 gallon batch. See how that works for you.

 

[Dale Owen]

Perfect! Thanks!