How to Make a Sourdough Starter from Scratch
Two ingredients, one jar, and about a week of patience. Here is how to grow a bubbly, reliable sourdough starter from flour and water.
A sourdough starter is nothing more than flour and water left to ferment until wild yeast and friendly bacteria move in and make it their home. You do not buy the culture — you cultivate it. In about a week, two humble ingredients become the engine that leavens every loaf you will ever bake.
What You Need
A clean glass jar, a kitchen scale, flour, and room-temperature water. Whole grain flour — whole wheat or rye — jump-starts the process because the microbes you want live on the grain. You can switch to plain bread flour once things get going. Avoid chlorinated tap water if yours is heavily treated; filtered or left-out water is safer for the young culture.
Day 1: Mix
Combine 50 grams whole wheat flour with 50 grams water in your jar. Stir into a thick paste, scrape down the sides, and cover loosely so gases can escape. Leave it somewhere warm, ideally around 24°C (75°F). Nothing will happen yet, and that is fine.
Days 2 to 3: First Signs
You may see a few bubbles and catch a sharp, slightly funky smell. This is the first wave of microbial activity, and it is often the wrong microbes — that is completely normal. Now begin daily feeding. Discard all but 50 grams of the mixture, then add 50 grams fresh flour and 50 grams water. Stir, cover, and wait.
Days 4 to 6: The Lull and the Surge
Many first-time bakers panic here. Around day three or four, the early activity often stalls and the starter goes quiet. Do not give up — the community of microbes is rebalancing. Keep feeding once a day. Soon you will see steady bubbles, a domed surface, and a pleasant, yogurt-like tang. Switching to a mix of bread flour and a little whole grain often speeds things along.
Day 7 and Beyond: The Float Test
Your starter is ready when it reliably doubles in size within four to eight hours of feeding and smells tangy rather than sour. Test it: drop a spoonful into water. If it floats, it is full of gas and strong enough to bake with. If it sinks, feed it again and wait a few more hours.
Keeping It Alive
Once your starter is established, you have two choices. Bake often? Keep it on the counter and feed it once or twice a day. Bake occasionally? Store it in the fridge and feed it once a week. To bake, pull it out, feed it, and let it come to life for a few hours before mixing.
Troubleshooting the Build
A thin layer of grey liquid on top — called hooch — simply means the starter is hungry; stir it in or pour it off and feed. A pink, orange, or fuzzy growth is different: that is spoilage, and you should throw the batch out and start over. Healthy starter smells sour, tangy, or beery, never rotten.
Naming your starter is optional. Feeding it is not. Treat it well and it will outlast every loaf pan in your kitchen.
A Realistic First Week
Do not expect a straight line of progress. A typical build looks like this: quiet on day one, a burst of false activity around day two, a discouraging lull mid-week, and then a genuine, rhythmic rise by day six or seven. Many bakers throw out a perfectly good starter during the lull, convinced they failed. Hold your nerve and keep feeding. Warmth is your biggest ally — a starter kept near 24 to 26°C will mature days faster than one shivering on a cold counter. If your kitchen is chilly, use your oven with only the light on, or set the jar on top of the fridge where it is a few degrees warmer. Consistency in feeding time and temperature does more than any special flour or bottled culture. Two weeks from now you will have a jar that predictably triples after every feeding, and you will wonder why anyone buys yeast at all.