Day One: To a clean jar, add 100g whole rye flour and 125g warm water (about 95°F). Stir until fully combined and there are no dry bits. Loosely cover and let sit for 24 hours.
Day Two: To a clean jar, add 75g of the mixture from Day One, 50g whole rye flour, 50g unbleached all-purpose flour and 115g water (room temperature). Stir until fully combined. Loosely cover and let sit for 24 hours. (Discard the remaining mixture from Day One)
Day Three: To a clean jar, add 75g of the mixture from Day Two, 50g whole rye flour, 50g unbleached all-purpose flour and 115g water (room temperature). Stir until fully combined. Loosely cover and let sit for 24 hours. (Discard the remaining mixture from Day Two)
Day Four: You will feed the starter twice. This is easiest if you do one in the morning and one in the evening. To a clean jar, add 75g of the mixture from Day Three, 50g whole rye flour, 50g unbleached all-purpose flour and 115g water (room temperature). Stir until fully combined. Loosely cover and let sit for 12 hours. (Discard the remaining mixture) After 12 hours, repeat the same steps for a second feeding and let mixture sit for 12 hours.
Days Five & Six: Repeat steps of Day Four, feeding every 12 hours.
Day Seven and Beyond: In the morning of Day Seven, in a clean jar, combine 10g of the mixture, 10g whole rye flour, 30g unbleached all-purpose flour and 40g water. (Discard the rest of the mixture from the previous feeding). Repeat this feeding twice a day, about 12 hours apart indefinitely. You can maintain your starter with just about any type of flour you like from this point.