Feed a starter, and when to ignore it

Once a starter rises reliably, keeping it is cheaper than starting again. The rule is the same one you used to raise it: discard most of the jar, then replace what you removed with flour and water.

For a baker who bakes often, a counter feeding is simplest. Keep about 20–30 g of ripe starter, stir in 50 g of flour and 50 g of water, and let it peak. At a room near 24 °C that peak is often four to six hours. Bake with it at the top of the rise, when the dome is just beginning to flatten. Past that, the yeast is tired and the loaf will be sluggish.

If you bake once a week, the fridge is the kinder place. Feed the jar, let it rise for an hour so the culture is awake, then cover it and chill. The cold does not stop fermentation. It slows it. The night before baking, take a spoonful, feed it at room temperature, and wait until that offshoot doubles. The mother jar can go back to the fridge unfed for another week. A grey liquid on top is hooch, alcohol from a hungry culture. Stir it in or pour it off, then feed. It is not spoilage.

Smell is the useful test. Ripe starter smells tangy and a little sweet, like yogurt and flour. A starter that smells of nail polish or rotten fruit needs a few regular feedings, not a funeral. Mould, pink streaks or an orange film are different. Those jars get composted, and you begin again from the seven-day method.

Write the feeding on the jar with a scrap of tape if you like: the weight of seed, flour and water. A 1:2:2 feeding (one part starter, two parts flour, two parts water) is calm and strong. A 1:5:5 feeding takes longer and tastes milder. Both are honest. The percentages in a recipe already assume you will count the flour and water inside whatever you add, which the calculator will do if you tell it they are there.