hotrod38 wrote:18-24 hrs. Take it out of the fridge the night before brew day. On the morning of brew day, feed the starter with some fresh wort to wake up the yeast and get them active. a half a cup would be enough.
+1, that's the best of both worlds. I usually use a pint to a quart of starter wort, or run off some wort from the chilled batch and hold it separate till the next morning.
I was a bit confused on this too, you here that it's good to pitch at high krausen but you also want to cold crash the starter to remove the spent oxidized wort (if agitating). I'm still not quite sure which is best, since if you pitch at high krausen the yeast will be active but at a lower cell count, and if you first cold crash you will have a higher cell count without the spent wort but less active. So the best of both worlds: let it ferment completely, cold crash, decant, then 'wake up' with fresh wort on brew day. It is important to keep the 'wake up' starter at the same temperature or lower than you intend to pitch the beer to avoid any thermal shock and associated lag. You do not want the 'wake up' starter to ferment completely since it will just deplete the yeast reserves, but 8-12 hours will be good enough to get it at high krausen.
