What a Healthy Starter Looks Like

A working sourdough starter is really a small, slow-motion ecosystem: wild yeasts that raise the dough and lactic acid bacteria that give it tang and keeping quality. When that balance is right, your starter will double in size within four to eight hours of feeding at room temperature, look domed and spongy, and smell cleanly sour — like natural yoghurt, ripe apples or a mild beer. It should not smell of acetone, nail varnish or damp socks; those are signs it has been left too long and is starving. If it has a layer of grey-brown liquid on top, that is hooch, and it means the same thing: feed me.

Reviving a Sluggish or Stalled Starter

Most sad starters are not dead, just cold and hungry. Give yours three days of attention and it will usually come back.

• Pour off any hooch and discard all but a tablespoon (about 20g) of the starter.
• Feed it with 50g strong white bread flour — or a mix of 40g white and 10g wholemeal rye, which is rocket fuel for a lagging culture.
• Add 50g of lukewarm water, around 25–28°C. Cold water slows everything down; water above 40°C will kill the yeast.
• Stir well, scrape down the sides, and cover loosely. A jar with the lid set ajar is ideal so gas can escape.
• Repeat every twelve hours at the same times if you can, discarding down to 20g each time.
• Keep it somewhere reliably warm, around 20–24°C. An airing cupboard, the top of the fridge or a microwave with the door shut and a mug of hot water inside all work well.

By day three you should see bubbles through the whole mixture and a clear rise. If you do not, keep going another two days before you blame the starter.

Adjusting Hydration for the Loaf You Want

Hydration is simply the weight of water as a percentage of the weight of flour. A starter fed with 50g flour and 50g water is at 100%, which is the most common way to keep one because it is easy to stir and easy to measure. From there, you can nudge it in either direction.

• Stiffer (60–75%): less sour, slower to peak, and far more forgiving if you forget it for a day. Good if you bake once or twice a week.
• Wetter (110–125%): ferments faster, tastes more sharply acidic, and suits rye and wholemeal loaves.

The practical trick is to change one thing at a time. If your starter separates within a day, thicken it slightly with an extra spoonful of flour. If it is a solid paste that barely bubbles, loosen it with a splash more water.

Is It Ready to Leaven a Loaf?

The famous float test — dropping a spoonful into water to see whether it floats — is unreliable and worth ignoring. Judge the starter itself instead.

• Volume: it has roughly doubled since feeding, within four to six hours.
• Structure: the top is domed and slightly taut, not sunken or cratered.
• Bubbles: active throughout the mass, not just a foamy crust.
• Smell: fresh, fruity and yoghurty, with a faint beery note.
• Taste: a dab on the tongue is pleasantly sour, not harsh or burning.

If you want certainty, run a small test: mix 50g starter with 100g strong white flour and 65g water, and leave it at room temperature. If it rises by about half within four to six hours, it will raise a loaf.

Temperature, Timing and the British Kitchen

Temperature matters more than any other variable, and British kitchens swing wildly between seasons. Aim for 20–24°C. In a cold January kitchen sitting at 14°C, fermentation can take three times as long as it does in July. Warm the flour and water slightly, park the jar somewhere insulated, or use a cool box with a hot water bottle tucked beside it. Above 28°C the yeast slows while the bacteria race ahead, and you end up with a thin, aggressively sour starter that struggles to lift dough.

A Rhythm That Fits Real Life

You do not need to feed a starter every single day. If you bake weekly, keep it in the fridge, take it out the night before, feed it 1:1:1 by weight and leave it overnight. If you bake most days, keep it on the counter and feed once daily at a higher ratio — one part starter to five parts flour to five parts water — which gives a slower, steadier rise and far less waste. Going away for a month? Spread a thin layer onto baking paper, let it dry completely, and crumble it into a jar. Add water and flour and it will wake up as good as new.

The longer you keep a starter, the more it settles into your kitchen and your habits. Be patient, jot down what you fed and when, and trust the signs rather than the clock. A reliable everyday loaf is mostly a matter of paying attention.