1 c. sour dough starter (see below)
1 pkg. active dry yeast
1 1/2 c. warm (110 to 115 degree) water
5 1/2 to 6 c. all-purpose flour
2 tsp. salt
2 tsp. sugar
1/2 tsp. baking soda

Bring sour dough starter to room temperature. In a large bowl, dissolve yeast in water. Stir in 2 1/2 cups flour, salt, sugar and starter. Combine 2 1/2 cups flour and soda; stir into sour dough mixture. Stir in as much remaining flour as you can mix in with a spoon. Turn onto a lightly floured surface. Knead in enough remaining flour to make a moderately stiff dough that is smooth and elastic, 6 to 8 minutes. Shape into a ball in greased bowl; turn once. Cover; let rise in warm place until double, 1 to 1 1/2 hours.

Punch down; divide in half. Cover; let rest 10 minutes. Shape each half into a 6-inch round or 9x4 inch oblong loaf on greased baking sheet. With sharp knife, make crisscross slashes across tops. Cover; let rise until nearly double, about 1 hour. Bake in 400 degree oven, 30 to 40 minutes. Remove from baking sheet; cool on wire racks.