Here is a little gem, fell out of my cookbook (guess he figured his time was ripe). It is like a Friendship Bread in that one is given Siegfried sourdough sample and a recipe with instructions. I think it's funny how it contains both metric and cups. I would just take a sample of your own sourdough and try it. How much? Anywhere from a tablespoon to 1/2 cup, up to you.... Thoughts & comments welcome.