Grease two bread loaf pans with butter and set aside.
To make the Salt Rising Bread, add enough all-purpose flour to the sponge to create a wet shaggy dough.
Pour this dough out onto a well-floured board and begin to knead lightly, incorporating the flour until the dough is no longer sticky. This should take no more than a minute to do. Do not over knead the bread.
Use a knife of bench scrape to cut the dough in half. Shape each half into an oblong loaf. One at a time, place one loaf into a prepared loaf pan.
Return the loaves to the warm place between 105-110 degrees Fahrenheit. Allow the loaves to rise in their loaf pans until they reach the rim of the loaf pan. This can take between 1-3 hours.
Once risen, remove the loaves from the warm place (if they are in the electric oven) but keep the loaf pans warm by covering them with a dish towel.
Preheat the oven to 400 degrees Fahrenheit. When the oven reaches the proper temperature, place the loaf pans on the middle rack of the oven.
Bread should bake for approximately 30 minutes. Once the tops are golden brown, the bread is ready.
Remove the loaf pans from the oven using oven mitts or pot holders and transfer to a cooling rack.
Allow the loaf pans to cool enough so that they can be handled comfortably. Remove each loaf of Salt Rising Bread from their respective loaf pans and place the bread onto a cooling rack.
Allow the bread to cool completely before slicing.