How to Make a Sourdough Starter From Scratch (7-Day Guide)

What a sourdough starter actually is

A starter is a simple mixture of flour and water that becomes home to wild yeasts and lactic acid bacteria. The yeasts produce the gas that raises bread, and the bacteria create the tangy flavor and acidity.

Once it is active and bubbly, you keep it alive by feeding it fresh flour and water. That maintenance schedule deserves its own attention, which is why daily feeding has a separate guide.

What you need to make a starter

You need an unbleached all purpose flour or whole grain flour, water free of chlorine, a clean jar, and a scale for accuracy. Whole grain or rye flour ferments faster because it carries more nutrients.

Avoid bleached flour if you can, since the bleaching process reduces the wild yeast population. Filtered or bottled water is best if your tap water is heavily chlorinated.

Day by day: the first seven days

Day 1: mix 1/4 cup (30 g) flour with 1/4 cup (30 g) water in a jar, stir well, cover loosely, and leave at room temperature. Days 2 and 3: add the same amounts each day and stir.

Days 4 to 7: begin discarding half the jar and feeding 1/4 cup (30 g) flour with 1/4 cup (30 g) water, once daily. By day 5 to 7 you should see bubbles, a rise, and a tangy smell within a few hours of feeding.

Choosing your flour

Whole wheat, rye, or a blend of all purpose and whole grain flour gives the fastest, most vigorous start because of the extra nutrients in the bran. Unbleached all purpose flour works too and gives a milder flavor.

You can switch flours once the starter is established. Many bakers keep a white starter for everyday bread and feed it whole grain now and then to keep the microbes active.

Troubleshooting a new starter

A dark layer of liquid on top is called hooch and simply means the starter is hungry; pour it off or stir it in and feed more often. A starter that smells like acetone is also just hungry.

If nothing happens by day 4 or 5, move it somewhere warmer, around 75F to 80F. If you see pink, orange, or fuzzy growth, throw the starter out and start over, because those are molds or harmful bacteria.

The float test and why it can mislead

The float test drops a spoonful of starter into water and sees if it floats, which suggests enough trapped gas to levitate the dough. It can be a helpful quick check but it is not definitive.

A starter can float while still weak or sink while perfectly ready, depending on hydration and how recently it was stirred. Judge readiness mainly by a consistent doubling within 4 to 8 hours of feeding and a domed, bubbly surface.

Handy Tips

• Use a clear jar and mark the starting level with a rubber band so you can see exactly how much the starter rises.
• Keep the starter warm, around 75F, for the first week; a cold kitchen is the most common reason a new starter stalls.
• Be patient. A starter that looks quiet on day 3 often surges on day 5, so resist the urge to start over too soon.

Frequently Asked Questions