I'm planning my first big beer, and I should need about 4 billion yeast. I have a 2L flask and have only done a few 1-step starters. I have looked at the Mr. Malty calculator and I understand that I'll need a 2 or 3-step starter for 4B, but my question is: can I do this in the 2L flask, or is that too small for so many yeast? Thanks for any advice.
No rule says you have to do it all at once. You could make a starter, decant, pour 90% into another container, and use the remaining 10% to make another starter
Here is a decent video on stepping up starters that you might find useful... http://homebrewacademy.com/stepping-up-a-yeast-starter
Assuming you're talking about 400B: A 2L flask will work just fine for a stepped starter. Ditch Mr. Malty and use yeastcalculator.com, or Brewers Friend, or Brewcipher . . . these guys all support stepped starters. Usually you can reach 400B with a moderately fresh packet, a stir plate, and a two step starter. As a rule, you don't want to exceed ~1.5 liters of wort in a 2L flask. Remember, yeast health is just as important as quantity. Let the calculator do all the heavy lifting . . .
