Day 1: Place a clean jar on the kitchen scale. Tare the scale to zero. Pour 50 grams of whole wheat flour and 50 grams of all-purpose flour into the jar. Add 125 grams warm (80-90ºF) filtered water. Stir well until the flour and water are incorporated. Cover lightly with the lid and store in a dark, warm place for 24 hours.
Day 2: Check on the starter. If you see nothing, let it sit for another 12-24 hours. Place a new jar on the scale. Tare the scale to zero. Add 75 grams of the fermented mixture to the jar. Discard the rest. Add 50 grams whole wheat flour and 50 grams all-purpose flour to the jar. Add 115 grams warm water. Stir well and cover loosely. Let rest in a dark, warm place for another 24 hours.
Day 3: Repeat the steps from day 2.
Day 4: Mix down the starter in the jar. Place a clean jar on the kitchen scale. Tare the scale to zero. Add 30 grams of the stirred-down mixture to the new jar. Discard the rest. Add 50 grams whole wheat flour and 50 grams all-purpose flour to the jar. Add 100 grams warm filtered water. Stir together and cover loosely. Store in a warm place for 24 hours.
Day 5 and onward: Repeat the steps of Day 4 until your sourdough starter is rising and falling predictably.
