I'm trying to learn more about sponges in breadmaking.
Most recipes that I've found for sourdough bread don't use a sponge. What does it add?
Also, what's a general rule of thumb for how to make one? From what I can gather, it looks like the sponge is just an extra-large batch of starter. By this, what I mean is: I refresh my starter with 50g water, 50g flour. It looks like sponges are essentially equivalent to refreshing a starter with 300g (or whatever) of each. Then the next day, you add some more dry flour until you get something solid enough to work with. Is this the gist of a sponge? If so, wouldn't the sourdough break down the gluten in the sponge, thereby greatly reducing the amount in the final product that you have to work with?