Unless you want a lighter loaf, use medium rye flour, which is darker and has more rye flavor than the more common white rye flour.
Combine in a large mixing bowl or the bowl of a heavy-duty mixer:
1 cup Sponge Starter
2 1/2 cups room-temperature (72┬░ to 75┬░F) water
3 1/2 cups medium rye flour
3 1/2 cups bread flour
Stir rapidly with a wooden spoon or on medium speed for about 2 minutes. Adjust the consistency of the dough by adding flour or water. Work in by hand for 2 minutes or with the dough hook on the mixer:
4 teaspoons fine salt, preferably sea salt
Knead by hand or with the dough hook on low to medium speed until the dough is smooth, elastic, and firm, about 7 minutes. Transfer the dough to an oiled bowl and turn it over once to coat. Cover the bowl tightly with plastic wrap and let rise in a warm place (75┬░ to 80┬░F) for 1 1/2 hours. The dough will rise only very slightly; do not leave it longer, or it will overferment the starter, which will make the bread heavy (yeast cells eat rye flour very quickly).
Divide the dough in half and shape each half into a round loaf (see Shaping). Place the loaves in 2 round proofing baskets or in two 1 1/2-quart bowls lined with oiled plastic wrap or on greased baking sheets sprinkled with:
Cornmeal
as free-standing loaves. Cover with oiled plastic wrap and let rise in a warm place for 1 1/2 hours. Preheat the oven to 450┬░ F. If using a baking stone, preheat it on the center oven rack for 45 minutes. If the loaves are not already on baking sheets, sprinkle the back of a baking sheet with a thin layer of cornmeal (use a baking sheet instead of a peel because the sticky dough sometimes clings to the peel). Quickly flip the bowls of dough onto the baking sheet, leaving several inches of space between them, and gently pull away the bowls and peel the plastic wrap away from the dough. Score the risen loaves (see Scoring). Spritz the preheated oven with water from a spray bottle, wait 1 minute, and quickly slide in the loaves. Spritz the oven walls again. Bake until well browned and the bottom of the loaf sounds hollow when tapped, about 45 minutes. Let cool on a rack.
