Starting and Keeping a Sourdough Starter
A sourdough starter is your workhorse for natural fermentation. Once you have one going, it becomes a kitchen constant—something you check on, feed, and rely on. Building one from scratch takes a week or so. Keeping one alive takes about five minutes a week.
What you're actually doing
You're creating an environment where wild yeast and lactic acid bacteria thrive. They live in your flour and water mixture and multiply through regular feeding. There's no magic—just consistency. Use unbleached bread flour or all-purpose flour. Tap water works fine; if your water is heavily chlorinated, let it sit overnight before using.
- Glass jar (1-quart or larger)
- Kitchen scale (optional but helpful)
- Wooden spoon or silicone spatula
- Cheesecloth or coffee filter (for covering the jar)
- Ruler or marking pen (to track rise)
What goes in.
- 50 gunbleached bread flour or all-purpose flour
- 50 gfiltered or tap water
Feeding at the right moment
A starter rises and then falls. Feed it when it reaches its peak—when the bubbles are fullest and the surface is visibly risen—not after it's collapsed. That's the sign the microbes are most active. If you miss the peak and it falls, it's still alive, just less vigorous. Feed it anyway.
The method.
Mix your first batch.
Combine 50 g flour and 50 g room-temperature water in a clean glass jar. Stir until no dry flour remains. The mixture should look like thick pancake batter. Cover loosely with cheesecloth or a coffee filter (you want air exchange, not contamination). Leave it on the counter at room temperature, ideally between 68°F and 75°F.
Wait and observe.
For the first 24 hours, nothing much happens. This is normal. You might see a few bubbles, or none. Don't panic. By day 2, you'll likely see a layer of liquid on top (this is called hooch—a sign of yeast activity) and some bubbles forming throughout the mixture. It may smell like nail polish or paint thinner. This is the bacteria doing its work. Not pleasant, but it passes.
Feed on day 2.
Discard half the mixture (about 50 g). Add 50 g fresh flour and 50 g water. Stir well. Cover loosely again. You're now in a rhythm: every 24 hours (or twice daily if your kitchen is warm), you'll discard half and feed with equal weights of flour and water.
Feed daily for days 3–5.
Repeat step 3 every 24 hours. By day 3 or 4, you'll notice the mixture becomes more active—more bubbles, faster rise after feeding. The smell shifts from harsh to sour and almost yeasty. You're seeing the balance shift away from acetic acid bacteria toward the more pleasant lactic acid bacteria and yeast. The mixture should rise visibly between feedings, sometimes doubling in volume within 4–8 hours of feeding.
Look for consistent rising.
By day 5 or 6, your starter should rise noticeably within 4–6 hours of feeding and be full of bubbles throughout, not just on the surface. The smell should be pleasantly sour—like yogurt or mild vinegar. When it reaches this point, it's ready to use. If it's still sluggish by day 7, keep feeding daily for another few days. Some starters take longer depending on temperature and flour type.
Transition to weekly feeding.
Once your starter is reliably active, move it to the refrigerator. Feed it once more before refrigerating (discard half, add equal parts flour and water, stir, then refrigerate). It'll slow down drastically in the cold. Once a week, take it out, discard half, feed it with fresh flour and water, let it sit at room temperature for an hour or two, then return it to the fridge. This keeps it alive without demanding daily attention.
Before baking, bring it to room temperature.
About 8–12 hours before you plan to mix dough, remove your starter from the fridge and feed it (discard half, add flour and water). Leave it on the counter. It should rise again, becoming bubbly and light. This is your signal it's strong enough to leaven bread. If it doesn't rise within that time, it may need an extra feeding or warmer conditions.
Other turns to take.
Twice-daily feeding (for faster development)
If your kitchen is warm (72°F+) and you want to establish a starter faster, feed it twice daily instead of once. Discard half and feed with equal parts flour and water every 12 hours. This can shorten the establishment phase to 4–5 days. The tradeoff is more frequent feedings until you refrigerate it.
Higher-hydration starter
Instead of equal weights flour and water (100% hydration), use 1 part flour to 1.5 parts water by weight (150% hydration). This creates a looser, pourable consistency that's easier to work with for some baking styles. The feeding ratio stays the same: discard half, add equal weights of flour and water.
Whole wheat or rye addition
Once your starter is established, you can feed it with 10–20% whole wheat or rye flour mixed into your white flour. These flours ferment slightly faster and can give your starter a bit more vigor. Stick with mostly white flour for predictability, but the addition can be helpful if your starter ever seems sluggish.
When it doesn't go to plan.
Temperature matters. A starter kept at 75°F will be more active than one at 65°F. If your kitchen is cold, the rise will be slower but the starter will still work—just plan for longer timelines.
Use a jar tall enough to see the rise clearly. Marking the side with a rubber band or pen line lets you track progress without guessing. You want to see at least some rise between feedings by day 4.
Don't sterilize your jar obsessively. Rinse it clean, but you want your starter to establish in a living ecosystem, not a sterile lab. A little residue from the previous feeding isn't a problem.
Hooch (the liquid that collects on top) is fine. You can stir it back in or discard it before feeding. It's just a sign the microbes have been busy. If there's a lot, your starter is hungry and wants feeding more frequently.
If your starter develops mold (fuzzy growth, usually pink or orange) or smells genuinely rotten, discard it and start over. A healthy starter should smell sour and yeasty, never putrid.
You only need a small amount of active starter to leaven bread—usually 50–100 g. Keep the rest in the fridge. You're not wasteful by discarding half at each feeding; you're keeping the culture healthy and manageable.
The ones that keep coming up.
How do I know when my starter is ready to bake with?
Your starter should rise noticeably (at least 50% increase in volume, ideally doubling) within 4–8 hours of feeding at room temperature. It should be full of bubbles throughout, not just on the surface. It should smell pleasantly sour. When you feed it and it reliably rises within those hours, it's ready. If you're still unsure by day 7, keep feeding daily—some starters simply take longer.
What if my starter isn't rising by day 5?
Check your kitchen temperature. If it's below 65°F, the fermentation is just slow. Move the jar to a warmer spot—the top of the fridge, a shelf near (not touching) a radiator, or inside a turned-off oven. Also make sure you're using unbleached flour; bleached flour can inhibit fermentation. If temperature isn't the issue, keep feeding daily. Some starters take 10–14 days, especially if you're using tap water with residual chlorine.
Can I leave my starter at room temperature instead of refrigerating it?
Yes, but it demands daily feeding. If you bake several times a week, room-temperature storage works well. You'll feed it once a day, and it's always ready. If you bake infrequently, refrigeration is easier—you feed once a week and it waits for you. There's no harm in either approach; it's a matter of your baking frequency and kitchen space.
Why does my starter smell like acetone or nail polish?
That's acetic acid bacteria taking over while the yeast is still establishing. It's not a sign of failure. Keep feeding daily, and the balance will shift toward yeast and lactic acid bacteria. Within a few more days, the smell will become pleasantly sour instead of harsh. This is completely normal in the first week.
What's the grey liquid on top of my starter?
That's hooch—a blend of liquid and metabolic byproducts from the microbes. It means your starter is hungry and wants feeding. You can stir it back in or pour it off before feeding; either way is fine. If there's always a thick layer, your starter wants feeding more frequently than your current schedule allows.
Do I need to use filtered water?
Tap water works fine in most places. If your tap water is heavily chlorinated, you'll notice it by smell. Letting it sit overnight allows chlorine to gas off. Filtered water is convenient but not necessary. The chlorine at typical tap levels won't kill your starter, just slow it slightly.
How long does a starter last?
Indefinitely, with feeding. Starters have been maintained for over a century. As long as you feed it regularly—daily at room temperature or weekly in the fridge—it will keep going. Even if you neglect it for months and it develops a dark liquid on top, it's usually still alive. Feed it and see if it revives.
Can I reduce the amount of starter I'm keeping?
Yes. Once it's established, you can feed smaller amounts. Instead of discarding half and adding equal parts flour and water, you can use a 1:5:5 ratio—1 part starter to 5 parts flour and 5 parts water by weight. This lets you maintain less volume. The feeding schedule stays the same: once weekly in the fridge, or daily at room temperature.