1 1/2 cups warm water
1 cup Sourdough Starter
4 cups unsifted all-purpose flour
3 teaspoons granulated sugar
1 1/2 teaspoons salt
2 to 2 1/2 more cups flour
1/2 to 1 teaspoon baking soda
Combine water, starter, 4 cups flour, sugar and salt in a glass bowl. Mix well, cover lightly with a towel folded into several thicknesses, and let stand at room temperature for approximately 18 to 24 hours or until the dough has doubled in size.
Mix 1 cup of the remaining flour with 1/2 teaspoon of the baking soda and stir this into the risen dough until it is very stiff. Turn the dough out onto a floured board and knead approximately 1 more cup of flour and a little more baking soda into it. Knead it for 5 to 10 minutes or until the dough is smooth. Shape into 2 long loaves or 1 large round loaf, place on a lightly greased baking sheet, cover, and let stand in a warm place for 3 to 4 hours or until almost doubled in size. You may wish to sprinkle cornmeal on the greased baking sheet or line it with kitchen parchment before placing the bread on it. Preheat oven to 400 degrees F.
To make a wash, bring 1 teaspoon cornstarch and 1/3 cup water to a boil in a small pan over low heat. Stir until it becomes thick and clear. Brush each loaf with it. OR brush a little water on top of the loaves and make a few diagonal slits across the top with a sharp knife. For a crustier bread, place a shallow pan of water in the bottom of the oven. Bake for approximately 45 to 50 minutes or until the crust is a medium dark brown.