Building a Sourdough Starter
A starter is not mysterious. It's flour, water, and time. Wild yeast lives on grain; bacteria lives in the environment. Feed them regularly and they multiply. Neglect them and they die. After a week of daily feeding, you'll have a culture that can leaven bread without commercial yeast.
What you're actually doing
You're creating a symbiotic ecosystem. Flour contains wild yeast and lactic acid bacteria. Water activates them. Daily feeding gives the fast-reproducing yeast a food source and the bacteria a stable pH to thrive in. The bacteria produce lactic and acetic acids—that's the sour flavor and the rise power. Room temperature (68–75°F) works best. Warmer speeds things up; colder slows them down.
- 1 clean glass jar (1 quart / 1 liter minimum)
- kitchen scale (essential for consistency)
- wooden spoon or chopstick for stirring
- cloth or coffee filter to cover the jar (breathable, not airtight)
What goes in.
- 50 gall-purpose or bread flour (unbleached preferred; no whole wheat yet)
- 50 gfiltered or dechlorinated water (chlorine can inhibit fermentation)
Consistent 1:1 feeding by weight
Use a scale, not eyeballing. Every day at roughly the same time, discard half the starter and feed the remainder with equal parts flour and water. This rhythm—discarding, feeding, waiting—mimics a reliable food supply. The yeast and bacteria synchronize to it. Consistency beats perfection.
The method.
Day 1: Make the first mix
Pour 50 g flour and 50 g water into a clean jar. Stir until no dry flour remains. The mixture should look like thick pancake batter. Cover loosely with cloth or a coffee filter secured with a rubber band—you want air exchange, not contamination. Leave at room temperature (68–75°F).
Day 2: Observe, don't feed yet
Look for any activity—bubbles, separation, a smell like yogurt or acetone. You might see nothing. This is normal. The yeast is waking up. Don't feed today. Just observe and cover it again.
Day 3: First feeding
Discard half the mixture (about 50 g). Add 50 g flour and 50 g water to what remains. Stir until combined. The jar should be about half full now. Cover and wait. You're looking for visible bubbles by tomorrow or the next day.
Days 4–7: Daily feeding cycle
Each day at the same time, discard half and feed with 50 g flour and 50 g water. The culture will start to smell sour around day 4 or 5. Bubbling might be vigorous one day and quiet the next—this is normal as bacteria acid levels shift. By day 5 or 6, you should see consistent rise and fall: the starter rises a few hours after feeding, then falls as it consumes the food. This cycle is the signal it's ready.
Readiness check: the float test
Around day 5–7, drop a small spoonful of starter into water. If it floats, it's mature enough for baking. If it sinks, keep feeding daily until it floats. You can also look for consistent rise 4–8 hours after feeding and a pleasantly sour smell. A mature starter bubbles actively, doubles or triples in volume after feeding, and has a consistent tan color with a slightly stringy, elastic texture.
Transition to maintenance
Once your starter passes the float test, you can refrigerate it and feed it once a week, or keep it on the counter and feed it once or twice daily depending on how often you bake. For storage, keep it in the fridge in a loosely covered jar. Feed it before refrigerating so it has fresh food. It will develop a dark liquid on top (hooch—expired alcohol and water). Stir it back in, or pour it off if you prefer a less boozy flavor.
Other turns to take.
Whole wheat starter
Whole wheat ferments faster than all-purpose because the bran provides more nutrients and surface area. If your first attempt stalls, try switching to 50% whole wheat and 50% bread flour. The culture will be more active, though the flavor will be earthier and less refined.
Rye starter
Rye ferments even faster than whole wheat. If you want a very active, pungent starter, use rye flour. It will be ready in 4–5 days and will have a distinctly sour, almost peppery edge. Use it as is or transition to all-purpose flour once it's established.
Quick-start method (using existing yeast)
If you're in a hurry, add a pinch of instant yeast to your first mix (less than 1/4 teaspoon). The commercial yeast gives you a head start while wild yeast colonizes. By day 3–4, the wild yeast takes over and you have a functional starter. This skips the waiting but doesn't create a purely wild culture.
When it doesn't go to plan.
Water matters: chlorine kills yeast. Use filtered water, or let tap water sit 24 hours to let chlorine evaporate. If your starter is sluggish after day 3, this is often why.
Temperature accelerates everything. At 75°F, a starter might be ready by day 5. At 65°F, it could take 10 days or more. If your kitchen is cold, keep the jar in a turned-off oven or a small insulated box.
Discard is not waste. Keep a jar of discarded starter in the fridge to make pancakes, crackers, or quick breads while you're building the main culture.
Smell changes mean progress. Day 2–3 might smell sharp or like nail polish (acetone). By day 5–6, a pleasant yogurt-sour smell means lactic acid bacteria are dominating. If it ever smells rotten or malty like beer gone wrong, toss it and start over.
Unbleached flour starts faster than bleached. Bleach inhibits fermentation. If you only have bleached flour, it will still work, but expect an extra day or two.
Never use soap on your jar. Rinse it with hot water. Soap residue can interfere with fermentation.
Keep your starter in the same spot. Moving it constantly or exposing it to drafts slows colonization. Pick a warm, stable corner.
The ones that keep coming up.
Can I use tap water?
Yes, but let it sit 24 hours first if your water is heavily chlorinated. Chlorine inhibits wild yeast. If you forget and use it fresh, the starter will still work—it just might take an extra day or two.
What if my starter smells like nail polish remover?
That's acetone from yeast metabolism. It's harmless. The smell means fermentation is happening. It will fade as lactic acid bacteria take over around day 4 or 5.
Can I use whole wheat flour from the start?
Yes. It ferments faster than all-purpose flour because the bran provides more nutrients. Your starter will be ready 1–2 days sooner, but the flavor will be earthier and less tangy.
My starter hasn't bubbled by day 5. Is it dead?
Probably not. Temperature is the most common cause of delay. If your kitchen is below 65°F, move the jar somewhere warmer. If the room is warm and you used filtered water, wait another 2 days. Some starters colonize slowly. As long as you're feeding it, keep going.
How much should I discard during feeding?
Roughly half. You're aiming to keep the ratio balanced—enough living culture to inoculate the new flour and water, but not so much that you're wasting. A 50/50 discard-to-feed ratio is the standard.
Do I need a special jar?
No. Glass is ideal because you can see activity, but any clean, non-reactive container works. Avoid metal if possible; glass or food-grade plastic is safer long-term.
Once my starter is ready, can I refrigerate it immediately?
Yes. Feed it, let it rise for 1–2 hours at room temperature, then refrigerate. It will stay active for weeks in the fridge with weekly feedings. When you're ready to bake, remove it, feed it, and let it come to room temperature and rise before using.