How to Make a Sourdough Starter From Scratch: Flour, Water and About Two Weeks

Quick answer: to make a sourdough starter, stir together 50 grams of whole wheat or rye flour and 50 grams of lukewarm water in a clean jar, cover it loosely and keep it somewhere around 75 to 80°F. Each day, discard all but about 50 grams and feed it 50 grams of flour and 50 grams of water. After 7 to 14 days, it should double within 4 to 8 hours of feeding, smell pleasantly sour and be ready to bake with.

What’s happening in the jar

Flour carries wild yeasts and lactic acid bacteria. Once you add water, they start eating the starches and multiplying. The yeast produces gas, which makes bread rise, and the bacteria produce acids, which give sourdough its tang and keep unwanted microbes out.

In the first few days, other bacteria often cause a burst of bubbles that looks like success. Then activity drops, sometimes to almost nothing. This quiet phase is normal. As the mix grows more acidic, the yeast and lactic acid bacteria take over, and steady, predictable rises follow.

What you’ll need

• Whole wheat or rye flour to start (more nutrients and microbes than white flour)
• Unbleached all-purpose or bread flour for later feedings, if you like
• Lukewarm water, about 80°F. If your tap water is heavily chlorinated, use filtered water or let tap water stand out overnight
• A clean glass jar of about 16 to 32 ounces with a loose lid or cloth cover
• A digital kitchen scale that reads in grams
• A spoon or small spatula, and a rubber band or tape to mark the level

A straight-sided jar makes it much easier to see how far your starter has risen. Our guide to the best sourdough starter jars explains what to look for, and a scale from our kitchen scales for bread baking roundup keeps feedings consistent.

Step by step

1. Mix the first batch. On day 1, combine 50 g whole wheat or rye flour with 50 g lukewarm water. Stir until no dry flour remains. It will look like thick paste.
2. Cover loosely and keep it warm. Rest the lid on top without sealing it, or use a cloth and rubber band. Set the jar somewhere around 75 to 80°F, away from direct sun.
3. Wait 24 hours. You may see a few bubbles, or nothing at all. Both are fine.
4. Discard and feed. On day 2, stir, then remove and discard all but about 50 g. Add 50 g flour and 50 g water, stir well and scrape down the sides. Mark the level with a rubber band.
5. Repeat daily. Feed the same way every 24 hours. From around day 4 or 5, you can switch to all-purpose or bread flour, or keep a mix of whole grain and white.
6. Move to twice a day when it’s active. Once the starter rises noticeably after each feeding, feeding every 12 hours helps it grow stronger and less sharply sour.
7. Watch for a reliable double. The starter is ready when it at least doubles in volume within about 4 to 8 hours of feeding, several days in a row, and has a domed, bubbly top and a yeasty, tangy smell.
8. Try the float test, if you want. Drop a spoonful into water at its peak. If it floats, it’s full of gas. A sinking starter may still be fine, so trust the rise more than this test.

Troubleshooting a slow or strange starter

No activity after day 3 or 4. This is the most common worry, and usually it just needs time. Keep feeding on schedule. Warmth helps the most: a spot near, but not on, a warm appliance, or the oven with only the light on (check the temperature with a thermometer, since some oven lights run hot). A proofing box for sourdough holds a steady temperature if your kitchen is cool.

A layer of gray or dark liquid on top. That’s called hooch, an alcohol byproduct that means the starter is hungry. Pour it off or stir it in, then feed. Feeding more often helps.

A smell like nail polish remover or old socks. Strong odors are common in the early days and as a starter gets hungry. They usually fade once it’s established and fed regularly.

Runny and soupy. Whole grain flour absorbs more water than white, so a starter can thin out after you switch. Use slightly less water, such as 50 g flour to 40 g water, until it thickens.

Pink, orange or fuzzy patches. These are signs of mold or unwanted bacteria. Throw the whole thing out, wash the jar and start again. Don’t try to scrape it off and save it.

Keeping your starter going

If you bake every day or two, keep the starter on the counter and feed it once or twice daily. If you bake weekly, keep it in the fridge once it’s strong. Feed it, let it sit at room temperature for an hour or two, then refrigerate. Feed it once a week or so, and take it out a day before baking to give it one or two room-temperature feedings so it’s lively again.

Discarded starter doesn’t have to go to waste. You can stir it into pancake or waffle batter, crackers or flatbread for extra flavor. If you skip discarding entirely, the jar overflows quickly and the starter gets diluted, so keep the amount small.

Once it doubles reliably, you’re ready for your first loaf. A simple place to start is no-knead Dutch oven bread, which you can adapt for sourdough, and when you’re ready for decorative cuts, see how to score sourdough bread.

Starter questions, answered

How long does it take to make a sourdough starter?

Usually 7 to 14 days, though a cool kitchen can stretch that to three weeks. It’s ready when it doubles within about 4 to 8 hours of feeding, consistently.

Do I really have to throw away part of my starter?

Yes, or use it in other recipes. Discarding keeps the jar from overflowing and gives the yeast enough fresh flour to stay active and balanced.

Can I make a starter with only all-purpose flour?

You can, but it often takes longer to get going. Starting with whole wheat or rye, then switching to white flour, is the more reliable route.

Should the lid be on tight?

No. Gas builds up as the starter ferments, so rest the lid on loosely or use a cloth cover.

What does a healthy starter smell like?

Mildly sour, yeasty and a little like yogurt or beer. Sharp smells can come and go when it’s hungry, but pink or orange streaks and fuzzy mold mean it’s time to start over.