Plan on 24 hours from start to finish for this sourdough bread.
1/2 cups warm water
1 cup sourdough starter (see preceding instructions)
4 cups unsifted regular all-purpose flour
2 teaspoons salt
2 teaspoons sugar
2 cups unsifted regular all-purpose flour (more or less)
1/2 teaspoon soda (or more)
Combine water, starter, the 4 cups flour, salt, and sugar. Mix well, place in a non-metallic container, and leave at room temperature about 18 hours, or until sponge has doubled in size. Stir in 1 cup of the remaining flour which has been mixed with the soda; the resulting dough will be very stiff. Turn dough out onto a floured board and knead, adding remaining 1 cup flour as needed. Knead until smooth, at least 8 minutes, until the dough cannot absorb any more flour.
Shape into two oblong loaves or one large round loaf. Place on a lightly greased cooky sheet, cover, and place in a warm place for 3 to 4 hours, or until nearly doubled in bulk. Just before baking, brush with water; make diagonal slashes in the top with a sharp knife or a single-edge razor. Place a shallow pan of hot water in the bottom of the oven. (For a more tender crust, do not place pan of water in oven, and brush unbaked loaf with salad oil or butter instead of water.)
Bake in a 400° oven until crust is a medium dark brown (about 45 minutes for the oblong loaves, 50 minutes for the large round loaf). For a heavier and tougher crust, remove loaf from oven IQ minutes before it is done; brush with salted water and return to a 425° oven for the remaining time.