Simple bread — Part 3 of 3
A sourdough starter is flour and water left to ferment. Wild yeast and bacteria from the flour and air colonize the mix, producing gas and acid that give sourdough its rise and tang.
Feed the starter on a schedule — discard half, then add fresh flour and water. A healthy starter doubles in volume within four to eight hours at room temperature and smells pleasantly fruity, not like nail polish remover.
Room temperature: Feed daily if you bake often. A small jar on the counter is enough for weekly loaves.
Refrigerator: Feed once a week. Bring the starter to room temperature and feed twice before baking so it is lively again.
Hydration: Equal weights of flour and water (100% hydration) are forgiving for beginners. Stiffer starters need longer fermentation.
Most recipes call for a portion of active starter plus additional flour, water, and salt. Longer bulk fermentation — often overnight in the fridge — develops flavor without extra yeast.
If the dough spreads instead of holding shape, try fewer stretch-and-folds, a shorter proof, or a slightly lower hydration until you learn how your starter behaves.