Building and Maintaining a Sourdough Starter
A sourdough starter isn't complicated, but it does demand consistency. The payoff is bread that develops flavor over hours of fermentation rather than minutes of commercial yeast, and a culture you can maintain indefinitely with nothing but flour, water, and routine. What follows is how to build one from scratch and keep it alive.
Temperature and timing matter more than precision
A sourdough starter thrives between 70°F and 80°F. Cooler kitchens slow fermentation; warmer ones speed it. Pick a feeding time and stick to it—morning or evening, doesn't matter. The routine is what the culture learns. You'll need a clean glass jar, a kitchen scale, and unbleached flour. Tap water works fine; if your water is heavily chlorinated, let it sit uncovered overnight first.
- Glass jar, 1-quart or larger
- Kitchen scale (digital preferred)
- Spoon or small whisk
- Cheesecloth or coffee filter (optional, for covering)
- Rubber band
What goes in.
- 50gunbleached all-purpose or bread flour
- 50gfiltered or dechlorinated water, room temperature
Feeding on schedule, not by feel
The culture needs predictability. Feed at the same time each day—the bacteria and yeast sync to your rhythm. If you skip a day or vary the time wildly, the starter gets confused and can languish or sour in the wrong way. Set a phone alarm if you have to. One daily feeding, every single day, is the load-bearing move.
The method.
Combine flour and water
Weigh 50 grams of unbleached flour into a clean glass jar. Add 50 grams of room-temperature water. Stir until no dry flour remains—you want a thick paste, like cake batter. This is your day-one mixture.
Cover loosely and let it sit
Cover the jar with a cloth, coffee filter, or loose lid—not airtight. You want air to reach the mixture. Leave it on the counter at room temperature, away from direct sun. Don't move it for 24 hours.
Observe day two
On day two, look for bubbles. You may see nothing. You may see a thin layer of liquid on top—that's hooch, alcohol produced by early fermentation, and it's fine. The smell should be mild, perhaps slightly yeasty or a bit funky. This is normal.
Begin daily feedings
Discard half the mixture—50 grams. Add 50 grams fresh flour and 50 grams fresh water. Stir well. Return the jar to the counter, loosely covered. Repeat this step at the same time every 24 hours.
Watch for activity, days three through five
By day three or four, you should see bubbles form within a few hours of feeding. They may rise and fall. The smell shifts from funky to pleasantly sour and yeasty—like yogurt or beer. If it smells like nail polish or acetone, it's fine; the hooch is doing its work. Keep feeding daily.
Test for readiness, day five onward
After the morning feed, watch the jar. When it doubles in volume within 4 to 8 hours, and you see steady bubbles throughout, the starter is mature. It should pass the float test: drop a small spoonful into cool water; if it floats, it's ready. If it sinks, keep feeding for another day or two.
Switch to maintenance mode
Once active, you have options. For daily baking: feed once a day on the counter. For weekly baking: feed, let it rise for 1 to 2 hours, then refrigerate. Before baking, remove from the fridge, feed, and let it come to room temperature and double—4 to 12 hours depending on the temperature.
Other turns to take.
Rye or whole wheat starter
Use rye or whole wheat flour for a portion of feedings—say 25 grams rye, 25 grams all-purpose. These ferment slightly faster and can give a tangier flavor. Adjust after day four if the fermentation is too vigorous.
Twice-daily feeding for faster maturity
Feed every 12 hours instead of 24. The culture matures in 4 to 5 days instead of 7. Use the same ratios: discard half, feed with 50g flour and 50g water. This pace demands more attention but works well in warm kitchens.
Refrigerator storage for irregular baking
Feed the mature starter, let it rise for 1 to 2 hours, then cap loosely and refrigerate. It can last 2 to 4 weeks between feedings. Remove, feed, and let it return to room temperature before use. Revive a neglected starter by feeding twice at room temperature over 24 hours.
When it doesn't go to plan.
If a dark liquid (hooch) pools on top, stir it back in—it's flavorful and harmless. If you prefer a milder flavor, pour it off before feeding.
Use filtered or dechlorinated water. Heavy chlorine can slow fermentation; let tap water sit overnight to let it gas off.
Keep the jar on the counter, not in a cabinet. You'll see activity and remember to feed it. Sight is your reminder.
If you forget a feeding and the starter looks crusty or smells like acetone, don't panic. Feed it twice over 24 hours and it usually rebounds.
Once mature, your starter will be hungry. Don't use a starter that hasn't doubled within 4 to 8 hours of feeding—it's still weak and won't leaven bread properly.
When it's time to bake, use the starter at its peak—when it's just finished doubling and the bubbles are visible but haven't begun to collapse. That's when the yeast and bacteria are most active.
A mature starter can sit in the refrigerator for weeks. When you're ready to bake again, remove it, discard half, and feed it twice over 24 hours at room temperature to wake it up.
The ones that keep coming up.
How long until I can bake with it?
Between 5 and 7 days, depending on your kitchen temperature. Warmer kitchens ferment faster. The true marker isn't time—it's consistency. The starter is ready when it doubles within 4 to 8 hours of feeding and passes the float test.
What if nothing is happening by day four?
Your kitchen is likely cool. Move the jar to a warmer spot—the top of the refrigerator, a sunny windowsill, or near (not on) a heat source. Fermentation slows dramatically below 70°F. Patience helps too; some starters take 10 days, especially in winter.
Is the gray or brown liquid on top normal?
Yes. That's hooch—alcohol produced by fermentation. It means the culture is active and hungry. You can stir it back in for extra tang, or pour it off if you prefer a milder starter. It's not spoilage.
Can I use tap water?
Depends on your tap water. If it's heavily chlorinated, let it sit uncovered for 8 to 24 hours to allow the chlorine to gas off. Filtered or dechlorinated water works best, but plain tap water works in most places.
What if it smells like nail polish remover?
That's acetone, produced during fermentation. It's harmless and will fade as the culture matures. Keep feeding daily. If the smell persists after day six, or if the starter never bubbles, it may not be viable—start fresh.
Can I use bread flour or whole wheat instead?
Yes to both. Bread flour ferments the same way. Whole wheat ferments slightly faster and produces a tangier culture. You can switch between them or mix them—the starter adapts.
What's the float test?
Drop a small spoonful of the starter into a cup of cool water. If it floats, the starter is full of gas and ready to leaven bread. If it sinks, it needs more feedings. It's a quick readiness check.
How long can a starter sit in the fridge?
Weeks, even months. Feed it, let it rise for 1 to 2 hours, cap it loosely, and refrigerate. Before baking, remove it, discard half, feed it, and let it come to room temperature and double—usually 4 to 12 hours. You can revive a neglected starter by feeding it twice at room temperature over 24 hours.
Do I have to throw away half at each feeding?
For a 1:1:1 ratio starter (equal parts starter, flour, and water by weight), yes. If you don't discard, the jar explodes out and feeding becomes unmanageable. If you want to reduce waste, you can use a lower feeding ratio—like 1:2:2 (starter to flour to water)—which requires less discarding but is trickier to master.
What if I can't feed it every day?
Refrigerate it. Feed once, let it rise slightly, and cap loosely. It will hold for weeks. When you're ready to bake, remove it, feed it twice at room temperature over 24 hours, then use it. This is how most home bakers manage a starter around a busy schedule.