How to Start a Sourdough Starter from Scratch

What a Sourdough Starter Really Is

A sourdough starter is nothing more than flour and water left to get on with it. Given a little warmth and a regular meal, the wild yeasts and friendly bacteria that live on grain and in the air of your kitchen will multiply, and what you end up with is a living, bubbling culture that lifts bread without a single gram of commercial yeast. It is the oldest leavening method in the book, and once you have one on your worktop you will wonder why anyone bothers with anything else.

The good news for beginners is that a starter is forgiving. It can be neglected for a fortnight, brought back from a grey layer of liquid, and still produce a beautiful loaf. You just need plain flour, water, a jar, and the willingness to be patient for about a week.

What You Will Need

Keep it simple. This is a rustic craft, not a laboratory exercise, and you almost certainly have most of it already.

• A jar — a 500ml to 1-litre glass jar, or a clean plastic tub. Something you can see through is best, so you can watch the bubbles rise.
• Flour — strong white bread flour is fine, but wholemeal or rye flour gets you going faster, because it carries more wild yeast and more minerals for them to feed on. A 50/50 mix of white and wholemeal is a lovely starting point.
• Water — lukewarm, around blood temperature. If your tap water is heavily chlorinated, draw a jug and leave it to stand for an hour or so, or use filtered water.
• Scales — weighing rather than scooping keeps everything consistent. Sourdough responds well to routine.
• A rubber band or a marker pen — for tracking how high your starter climbs.

Skip the sealed kilner lids in the early days. A loose lid or a piece of cloth secured with an elastic band lets gases escape. Trapped gas builds pressure, and nobody wants a floury explosion in the airing cupboard.

The First Week, Day by Day

Find a spot that sits between 20°C and 24°C — a kitchen cupboard above a fridge, a shelf away from the window, or the corner of a worktop. Below 18°C everything slows to a crawl; above 30°C you will encourage the wrong sort of microbes.

Day one. Weigh 50g of flour into your jar, add 50g of lukewarm water, and stir until you have a thick, sticky paste with no dry patches. Scrape down the sides, cover loosely, and leave it alone.

Days two and three. You will likely see a burst of activity — bubbles, a rise, a beery smell. Do not get excited. This is often a false start, driven by bacteria that will soon die back. Feed once a day: discard half the mixture, then add 50g flour and 50g water and stir well.

Days four and five. The lull arrives. Your starter may go quiet, smell sharply of acetone or nail varnish, and separate into floury sludge with liquid on top. This is normal and it is the stage where most people give up. Keep feeding once daily and push on.

Days six to ten. The culture settles into its rhythm. Feed twice a day if you can, still discarding half first. You are looking for a starter that doubles in size within four to six hours of feeding, dome-topped and honeycombed with bubbles, smelling of yoghurt, apples or fresh bread.

Reading the Signs

Your starter talks to you constantly. Learn its language and you will never need a recipe to tell you what to do.

• Risen and domed: happy and ready to bake with.
• Flat with dark liquid on top: hungry. Pour off the liquid, discard, and feed it.
• Thin and soupy: too warm or underfed. Move it somewhere cooler and feed more regularly.
• Thick and sluggish: often too cool, or your flour is very refined. A spoonful of rye in the feed perks it up.
• Pink, orange or furry: mould. Throw it out and begin again — this is the one problem patience will not fix.

A simple test: drop a teaspoon of active starter into a glass of water. If it floats, it is buoyant with gas and ready to leaven a loaf.

Keeping It Alive Long Term

Once your starter is reliably doubling, you have two choices. If you bake most weeks, keep it on the worktop and feed it daily, discarding the excess — or better still, save the discard in a tub in the fridge for pancakes, crumpets and scones. If you bake less often, move the jar to the fridge after a feed. Cold slows everything right down, and it will happily sit there for two or three weeks.

Before baking, take it out, pour off any dark liquid, and give it two or three feeds over a day at room temperature to wake it up. Always feed with the same ratio you started with — equal weights of flour and water — and always keep back some of the old culture to inoculate the new.

Name it if you like. Many bakers do. A starter that gets talked about gets fed, and a starter that gets fed becomes the quiet backbone of your kitchen: the thing that turns flour, water and time into something far greater than the sum of its parts.