Great info, SanPancho! If I wanted to make more all at the start, could I add more wort after running through the whole yeast starter/cold crash/decant cycle? Then I would just throw it on the stir plate again for another cycle?
yes, and no. let's say you'd start with your vial or pouch of yeast, then make something like a 1 liter starter. once that's done, then you most likely have to "step up" to a 2 liter starter, or 3, 4, 5 liter etc.
in general, you cant repeat a starter size- doesnt work like that. the yeast can sense that there isnt enough food for them to need to multiply themselves- so instead they sense that there are plenty of them around to do the job and they just go straight to fermenting.
a good yeast calculator will tell you that your starter is too small- typically it'll state that yeast is at "maximum density/cell count/etc." time to step up to a larger starter size.
if you dont have enough equipment for multiple step up starters (i.e. just a single 1liter flask?) then you have two options.
1-split up the yeast vial/pouch you buy into two starters. pour half into a starter. when that's done, make another starter out of the remaining yeast. then you can split and save those batches.
2- do like kh54s10 describes where you just grow an extra large starter. for instance, if you need 300b cells, you grow 400b instead. pitch your 300b and then keep the extra 100b on hand. then just repeat the process next time you need yeast to pitch.
if you are going to be using the same yeast and brewing on something like a weekly basis- then make a huge batch all at once. save yourself the time and headache.
but if you're only gonna brew once or maybe twice a month, you can probly just make bigger starters and save a bit for later.
and yes- dont freeze your yeast unless you have specifically prepared it for freezing.
