Combine 1 cup of whole wheat or rye flour with ½ cup of water thoroughly in a non-reactive container. Leave the container out at room temperature for 24 hours. Cover the container with cheesecloth and a rubber band.
On Days 2 and 3, discard half the starter and add 1 cup all-purpose flour and ½ cup water. Combine and let sit at room temperature for 24 hours.
On Day 4, feed your starter every 12 hours with 113 grams of starter, 113 grams of all-purpose flour, and 113 grams of water.
On Day 5, continue the same feeding process every 12 hours until your starter is bubbly and has doubled in volume.
