What You Are Actually Keeping

A sourdough starter is a living culture of wild yeasts and lactic acid bacteria, and it behaves far more like a pet than a pantry ingredient. You are not maintaining a product; you are maintaining a population, and that population is always responding to what you give it and how warm it is. Get the rhythm right and it will reward you for years, sometimes decades, producing bread with a depth of flavour no commercial yeast can imitate.

The two things that matter are food and temperature. Everything else — the jar you use, the flour you choose, how often you clean the sides — is a detail around those two pillars. Understand them and the rest follows.

The Standard Feed: Equal Parts by Weight

The simplest reliable method is a 1:1:1 feed by weight: one part starter, one part flour, one part water. If you keep 50g of starter, feed it 50g of flour and 50g of water. This gives you 150g of refreshed starter, enough for a loaf and a little left over to carry on with.

Weigh everything. Cups and spoons vary far too much, and a starter that is too wet will ferment quickly and turn sour, while one that is too stiff will rise slowly and taste mild. A thick, pourable batter — a bit like a slow-moving porridge — is the aim for most white-flour starters.

On the flour itself, a strong white bread flour gives a gentle, versatile starter. Swapping in a spoonful of wholemeal or rye adds minerals and enzymes that the yeasts adore, and it will noticeably speed things up. Rye starters are famously vigorous, though they do tend to be stickier and greedier. Whatever you choose, keep it consistent so you learn how your particular culture behaves.

Water should be lukewarm at most — never above 30°C, which can harm the culture — and ideally not straight from a heavily chlorinated tap. Leaving water to stand for an hour, or using filtered water, is a small courtesy that pays off.

Adjusting Ratios to Your Schedule and Kitchen

The 1:1:1 feed suits a starter kept at room temperature and fed daily. But most of us do not bake every day, and this is where ratios become genuinely useful rather than fussy.

• 1:1:1 — fed daily, ready in roughly four to six hours at 20–22°C. Ideal for a busy baking week.
• 1:2:2 — a little more breathing room, ready in six to eight hours. Good for a starter fed once a day in a warm kitchen.
• 1:5:5 — a long, slow feed that will hold for twelve hours or more at room temperature, or several days in the fridge. Useful if you want to feed in the evening and bake the following morning.
• 1:10:10 — a large feed to wake up a neglected starter or to build a big quantity for several loaves at once.

Temperature works alongside ratio, not against it. A starter at 24°C will race through a 1:5:5 feed in half the time it takes at 18°C. In a cold British kitchen in January, you may find yourself feeding more often than you expected; in a hot August, the opposite. Learn to judge by the starter rather than the clock.

The Fridge Is Your Friend

If you bake once a week or less, keep your starter in the fridge. A chilled starter enters a slow, sleepy state and needs feeding only every seven to ten days. Take it out the night before you plan to bake, pour off any dark liquid on top, discard all but a spoonful, and give it a generous feed. Two or three refreshments at room temperature over twelve to twenty-four hours will bring it back to full vigour.

Never seal the jar tightly. The culture produces gas, and a clamped lid invites a messy explosion. A loose lid, a piece of cloth secured with a band, or simply a jar placed at a slant will do.

Reading the Signs

A healthy starter at its peak is domed, bubbly, spongy and smells pleasantly of yogurt, apples or beer. Here is how to interpret the other signals.

• Dark liquid on top — this is hooch, a sign of hunger. It is harmless. Pour it off, or stir it in for a sharper flavour, then feed generously.
• Nail varnish or acetone smell — the culture is over-fermented and starving. Discard most of it and give two or three large feeds in quick succession.
• No rise at all — usually cold, or fed with flour that has lost its strength. Warm it gently and feed with fresh flour.
• Pink, orange or furry growth — this is mould, not yeast. Do not try to salvage it. Bin the lot, sterilise the jar and begin again.

Keeping the jar clean above the level of the starter helps prevent mould taking hold in the first place. A quick wipe with a damp cloth after each feed is worth the ten seconds.

Fitting a Starter into a Busy Week

Choose a rhythm you can genuinely keep. A starter fed at the same time each day quickly settles into a predictable pattern, and predictability is what makes baking feel calm rather than chaotic. If you work long hours, keep it in the fridge and revive it on Thursday for a weekend bake. If you bake often, leave it out and feed it daily, using the discard in crumpets, pancakes, scones or a batch of drop scones for breakfast.

Do not chase perfection. A slightly neglected starter that gets a good feed before baking will outperform a coddled one that is fed to a strict timetable you resent. Keep it warm, keep it fed, and it will keep you in good bread for years to come.