Short answer
A sourdough starter is a living culture of flour and water, home to wild yeast and lactic acid bacteria, that makes bread rise and gives it a tangy flavour. You keep it alive by feeding it regularly with fresh flour and water.
A sourdough starter is a live culture of flour and water in which wild yeast and lactic acid bacteria grow together. The yeast produces the gas that makes dough rise, while the bacteria give sourdough its gentle tang. Feed a starter regularly with fresh flour and water, and it will keep making bread for years.
What is a sourdough starter made of?
A sourdough starter is made of just two ingredients: flour and water. The microbes are not added from a packet. They already live on the flour, in the air and on your hands, and they multiply once the mixture sits somewhere warm.
Two groups of microbes matter. Wild yeasts produce carbon dioxide, which inflates the dough. Lactic acid bacteria produce acids, which add sourness and help the loaf keep. Because the two share the jar, a healthy starter is a small, stable ecosystem rather than a single ingredient.
Many bakers also call the starter a “levain”, the French word for a leavening culture, or a “mother”, though that term is more often used for vinegar. Sourdough starter is the common name in British and American kitchens.
How does a sourdough starter work?
A sourdough starter works by feeding wild yeast and bacteria with the sugars released from flour. As the microbes eat, they release gas and acid. The gas gets trapped in the stretchy gluten network of the dough and makes it rise.
Each feeding follows the same pattern:
- The fresh flour and water give the microbes new food.
- Over a few hours the culture bubbles and rises.
- At its peak the starter is domed, full of bubbles and ready to bake with.
- As the food runs out, the starter slowly sinks back and becomes hungry again.
This rhythm is why timing matters. A starter used at its peak lifts a loaf well, while one used long after its peak is weaker and tastes sharper.
What does a ready sourdough starter look like?
A ready sourdough starter has roughly doubled in the jar, has a domed top, and is full of bubbles of different sizes. It smells fresh and slightly sour, and a spoonful drops off the spoon in a soft, airy way.
A simple way to track this is to put a rubber band or a strip of tape on the jar at the level of the starter just after feeding. When the culture has risen well above the mark and the top is still domed, it is at its peak. A flat or collapsed top means the peak has passed.
Some bakers use the float test, dropping a small spoonful into a glass of water. A floating spoonful has trapped plenty of gas. The test is a rough guide only, since stirred or heavy starters can float or sink for other reasons.
How do you feed a sourdough starter?
You feed a sourdough starter by keeping a small amount of the old culture and mixing it with fresh flour and water. A common ratio is one part starter, one part water and one part flour by weight, often written 1:1:1.
A basic routine looks like this:
- Spoon out most of the starter, leaving about 50 g in a clean jar.
- Add 50 g of flour and 50 g of lukewarm water.
- Stir until no dry flour remains and scrape down the sides.
- Cover loosely so gas can escape, and leave somewhere at about 20 to 25°C.
- Mark the level and watch it rise over the next four to twelve hours.
Plain strong white bread flour works well, and many bakers add a spoonful of wholemeal or rye for extra food. Use whatever flour you have, and keep the routine steady.
How often should you feed a starter, and where should you keep it?
A starter on the worktop needs feeding once or twice a day, while one in the fridge needs feeding about once a week. Heat speeds the microbes up, and cold slows them right down.
| Where it lives | Feeding rhythm | Best for |
|---|---|---|
| Worktop, 20 to 25°C | Once or twice daily | Bakers who bake several times a week |
| Fridge | About once a week | Occasional bakers |
| Cold spell or holiday | Fed, then fridge for a longer pause | Short breaks away from baking |
Before baking from a fridge starter, take it out, feed it, and let it become active again over one or two feeds. A cold starter straight from the fridge is slow and can make a flat loaf.
What is sourdough discard?
Sourdough discard is the portion of starter you remove before each feed. It is still perfectly good, only less active than a freshly fed culture. If you never removed any, the jar would quickly overflow and the feeds would become wasteful.
Discard can go into pancakes, crackers, flatbreads and waffles, where it adds flavour rather than lift. A jar of discard keeps in the fridge for about a week. Some bakers also use it in a pizza base alongside baking powder or a little yeast.
What problems can a starter have?
Most starter problems come from temperature, hunger or the wrong flour, and most are easy to fix. The table below lists the usual signs.
| Sign | Likely cause | What to do |
|---|---|---|
| No bubbles after a week | Room too cool | Move somewhere warmer and keep feeding |
| Grey liquid on top | Hungry starter | Stir it in or pour it off, then feed |
| Sharp nail polish smell | Very hungry | Feed more often or use more flour |
| Pink or orange streaks, fuzzy mould | Contamination | Throw it away and begin again |
The grey or brownish liquid is often called “hooch” and is harmless. It simply tells you the culture wants food.
How is a sourdough starter different from packet yeast?
A sourdough starter is a mixed culture that rises slowly and adds flavour, while packet yeast is a single, fast-acting strain of baker’s yeast. A starter takes hours to raise a loaf. Packet yeast can do it in one or two.
Starter loaves tend to have a tangier flavour and a chewier crumb because the long fermentation develops acids and flavour compounds. Packet yeast breads are milder and more predictable. Neither is more authentic than the other, and many bakers use both depending on the loaf.
What does Weirdough Bakery say about its sourdough?
Weirdough Bakery in Walthamstow, London, sells sourdough loaves, and its Deliveroo listing describes them as made with organic flour from a watermill. The listing names a pain de campagne and a baguette tradition among its breads, and the bakery also bakes sourdough muffins, according to reviewers.
None of the public sources describe how the bakery runs its own starter, so this guide makes no claim about it. The starter advice above is general. For current loaves and opening times, see the menu page and the hours and location page. This guide is independent and takes no orders.
Common questions
How often should I feed a sourdough starter?
A starter kept at room temperature is usually fed once or twice a day. One kept in the fridge can be fed about once a week. Warmer rooms make the culture hungrier, so it needs feeding more often.
Can I use tap water for a starter?
Yes, in most homes tap water works. If your water is strongly chlorinated, let it stand in an open jug for a few hours first, or use filtered water, because strong chlorine can slow the culture.
What does a healthy starter smell like?
A healthy starter smells pleasantly sour and yeasty, a bit like yoghurt or ripe fruit. A sharp nail polish smell means it is hungry and needs feeding. Pink streaks or fuzzy mould mean you should throw it away.
How long does a starter last?
With regular feeding a starter can last indefinitely. Some bakers say they keep cultures going for many years, and starters are often shared between friends. A neglected one may need several feeds to wake up again.
Planning a visit? Start with Weirdough Bakery: address, opening hours, menu and directions in one place.
This article is general information from an independent guide, not from Weirdough Bakery itself. For the store’s current details see hours and location.