It's in your Day 1 description:
Day 1: Combine 4 ounces (1 cup) whole rye flour (pumpernickel) or whole wheat flour with 4 ounces (1/2 cup) non-chlorinated cool water in a non-reactive container. Glass, crockery, stainless steel, or food-grade plastic all work fine for this. Here, I’m using a 4-cup glass measure.
Day 2: Either way, discard half the starter (4 ounces), and add to the remainder 4 ounces (a scant 1 cup) King Arthur Unbleached All-Purpose Flour, and 4 ounces (1/2 cup) cool water (if your house is warm); or
October 8, 2013 at 3:46pm