Late afternoon or evening, grow your culture for the bread you are making the next day.  The warmer your kitchen, the faster the sourdough acts.  A cool kitchen will result in a slower acting sourdough.  Mix the following and let set out in your kitchen.  

• 1 cup sponge culture (consistency of pancake batter)
• 3 cups flour
• 1 cups warm water

The next morning:

1. Punch down the dough.
2. Dissolve 2 teaspoons of salt in 1 cup of warm water.
3. Mix the dough with 3 more cups of flour and the salt water mixture.
4. Knead dough until smooth and elastic, adding flour as necessary.
5. Shape loaves and let rise all day, the time it takes will depend on how warm your kitchen is.
6. Preheat oven to 375 degrees.
7. Use a very sharp knife or razor blade and cut slits in tops of loaves to allow gas to escape while it bakes.
8. Mix an egg with 2 Tablespoons of water and brush over the tops of the loaves. Alternatively, use water and no egg to wash over loaves.
9. Bake for 40-45 minutes.
10. Remove from pans and let cool on racks.