Yeast Starter Trouble.

[Brounds24]

So I'm Making an IIPA with a starting gravity of 1.090 and am shooting for a Final gravity of about 1.020. My recipes calls for a 9L starter, which I think is incredibly high!. I know if you make a liter starter you can get roughly 100 billion yeast cells if im not mistaken. Also if my maths right, on a beer with 90 points and roughly 4 billion cells needed per point I need roughly 360 billion cells. I don't see why a 9L starter is needed when I can make 4L starter. I am using Wyeast 3864 that was manufactured on 10/2/12. I made a gallon starter last night and before bed (roughly midnight when I pitched the yeast) I check it this morning at 7 before work and it was working well and when I came home for lunch at 1 it was ready to blow the airlock off the gallon fermenter! I sanitized all my equipment and used moonshine in my airlock so there should be no contamination (hopefully). I sanitized 5 quart jars and placed foil over them to give them more head space. Do I need to make more starter? Also is 24 hours long enough for my start to produce enough cells or should I give it a full 48. Thank you for all the help!

 

[eastoak]

i would make a 3-3.5 liter starter, wait until it finishes fermenting, decant and pitch. might take 24 hrs might take 48 depending on various factors like temp and stir plate use.