Floured proofing baskets add a spiral like this to the top of your sourdough loaf. You can also proof in a glass, metal or plastic bowl.
These three sourdough starters are all derived from a four-month-old culture; from left to right: a bread flour culture, a whole wheat culture and a rye culture.
You know a sourdough loaf is ready when you knock the bottom and it makes a hollow sound. Many bakers enjoy this stage the most; as the crust contracts, it makes crackling sounds, known as the “song” of the bread.