How to Make a Sourdough Starter From Scratch

This guide is for home bakers who want to grow their own sourdough starter but feel confused by conflicting advice online. You will learn what a starter is, exactly what to do each day, how to tell when it is ready, how to fix common problems and how to keep it alive with minimal effort. All you need is flour, water, a jar and a little patience. Hygiene points are general information, not professional advice; follow your local food-safety guidance.

What a Sourdough Starter Actually Is

A sourdough starter is a mixture of flour and water that has been fed regularly until it hosts a stable community of wild yeasts and lactic acid bacteria. These microbes are naturally present on flour, on grain and in your kitchen. The yeasts produce carbon dioxide gas, which makes bread rise. The bacteria produce acids, which give sourdough its tang and help keep unwanted microbes out.

Making a starter is really a process of encouraging the right microbes and discouraging the wrong ones. In the first few days, many different bacteria compete, and the jar may bubble wildly and then go quiet. As the mixture becomes more acidic, the useful yeasts and bacteria take over. After about one to two weeks of regular feeding, most starters settle into a predictable pattern: they rise, peak and fall back at roughly the same time after each feed.

What You Need

• Flour: Wholemeal (whole wheat) or wholegrain rye flour gets a starter going fastest, because it carries more natural microbes and nutrients. You can switch to plain white bread flour once the starter is established, or keep a mix.
• Water: Ordinary tap water is usually fine. If your water is heavily chlorinated and the starter struggles, use filtered water or leave tap water in an open jug for a few hours first.
• A glass or plastic jar: Around 500 ml to 1 litre, with straight sides so you can see the rise. A loose lid or a cloth secured with a rubber band is ideal.
• Kitchen scales: Weighing is far more accurate than cups and makes troubleshooting much easier.
• A spatula or spoon for stirring, and a rubber band or tape to mark the level after each feed.
• A warm spot: Somewhere around 24 to 27 C (75 to 80 F) is ideal. A cooler kitchen works too, just more slowly.

Wash the jar and tools in hot soapy water and rinse well before you start. Every few days, you can transfer the starter to a clean jar to keep dried crusts from building up around the rim.