A jar of flour and water

A sourdough starter is the oldest tool in the kitchen that is also alive. Flour, water, a jar, and a week of paying attention, and you have something that will raise bread for as long as you keep feeding it.

What is living in there

Two things, working side by side. Wild yeasts eat the sugars in the flour and give off carbon dioxide, and that is what lifts the loaf. Lactic acid bacteria eat what the yeasts leave behind and turn it gently sour, and that is what keeps the jar safe and gives the bread its flavour. Neither of them is added. Both of them arrive on the flour.

Feeding it

A feeding is one part starter, five parts flour, five parts water, by weight. Bakers write it as 1:5:5, and once a day is plenty for a jar that lives on the counter.

 20 g  starter
100 g  flour
100 g  water

Warm kitchens work faster than cold ones, so the clock is a worse guide than the jar itself. If you would rather bake once a week than once a day, keep it in the fridge and feed it the night before, the way the minimal example keeps things small.

Reading the jar

It rises, domes, and then falls. Use it at the dome.
It should smell of yogurt and apples, never of nail polish.
A spoonful floats in a glass of water when it is ready.

Just fed, at the dome, and fallen back.

A starter that has gone quiet is almost never dead. It is usually cold, hungry, or being fed too much at once. Halve the flour, warm the room, and give it three days. If you want to watch the whole thing read itself again, go back to the front page.

Written for this demo. Your grandmother’s method is better.