Starting a Sourdough Culture from Scratch
Building a starter requires patience but almost no skill. You're not creating anything exotic—you're simply providing conditions for wild yeast that already lives on grain and in the air to multiply. Watch it go from inert paste to vigorous, living culture. Once it's strong, it becomes the foundation for every loaf you bake.
What you're actually doing
You're feeding flour and water to invisible microbes until they become numerous and active enough to reliably leaven bread. The process is slow because you're starting from nearly nothing. Temperature matters—warmer environments (68–75°F) move faster. Colder kitchens take longer, and that's fine.
- a clean glass jar or container (at least 1 quart)
- kitchen scale (optional but helpful)
- spoon for stirring
- cheesecloth or coffee filter (optional, for covering)
What goes in.
- equal parts by weightall-purpose or bread flour
- equal parts by weightfiltered or dechlorinated water (chlorine can inhibit fermentation)
Consistent daily feeding at the same ratio
The starter becomes active not through magic but through repetition. Feed it the same amount of flour and water at roughly the same time each day. Consistency builds a predictable rhythm the microbes can thrive in. Skip a day and the culture slows. Miss a week and it may die, but one missed day is fine.
The method.
Day 1: Mix your base
Combine 50 grams of flour and 50 grams of water in your jar. Stir until no dry flour remains. You're looking for a thick paste, not a batter. Cover loosely with cheesecloth or leave the lid slightly cracked—the culture needs air, so don't seal it tight. Leave at room temperature.
Days 2–3: Discard and feed
Once a day, discard half the mixture (roughly) and add 50 grams flour and 50 grams water. Stir well. You'll see little activity at first—maybe a few bubbles, maybe nothing. This is normal. Keep feeding. The jar will smell sour and slightly unpleasant. This is the bacteria working.
Days 4–5: Watch for reliable rise
By now you should see consistent bubbles throughout and a noticeably sour smell. The starter should rise noticeably within 4 to 8 hours of feeding—this is the yeast becoming active. If it's still flat and sluggish, keep feeding daily. Warmer kitchens reach this point faster.
Days 5–7: Test for readiness
Your starter is ready to use when it doubles reliably within 6 to 8 hours of feeding and has a pleasant sour smell. Do a float test: drop a small spoonful into water. If it floats, the fermentation is vigorous enough to leaven bread. If it sinks, feed it for another day or two.
Establish a maintenance routine
Once active, feed your starter once daily if you keep it at room temperature, or once a week if you refrigerate it. At room temperature, feed it before you use it for bread. Refrigerated starters need a feeding 24 hours before you plan to bake, brought back to room temperature and fed again, so they're bubbly and ready.
Other turns to take.
Whole wheat or rye starter
Substitute whole wheat or rye flour for some or all of the all-purpose flour. These ferment slightly faster because their bran particles feed the microbes more quickly. The culture will be darker and smell earthier.
Reduced maintenance (refrigerated method)
After Day 2, move the jar to the refrigerator and feed it once weekly instead of daily. It slows fermentation dramatically, which is fine—the culture remains alive dormant. Pull it out 24 hours before baking, feed it twice at room temperature with 8 hours between, and use it when bubbly.
Building from a friend's starter
If someone gives you a spoonful of their active starter, you can skip the long initial wait. Feed it once, wait 6 hours, and check for reliable rise. Usually ready within 24 hours.
When it doesn't go to plan.
Use filtered or boiled water if your tap water is heavily chlorinated. Chlorine inhibits fermentation. Tap water that's been sitting uncovered for 24 hours works too.
Keep your jar somewhere consistently warm—the top of the refrigerator, a kitchen counter away from drafts, or inside an oven with the light on. Warmth accelerates activity; cold slows it.
The smell of a young starter is sour and slightly unpleasant, sometimes like old gym socks. This is normal and means bacteria are doing their job. Once it's fully active, the smell becomes more pleasant and yeasty.
If you see a dark liquid on top (called hooch), it's not bad—it's alcohol from fermentation. Stir it back in or pour it off; either way, just feed as usual.
Don't overthink cleanliness. Your starter doesn't need sterile conditions. A clean jar and unwashed spoon are plenty. The acidity of the developing culture prevents harmful bacteria from taking hold.
Once your starter is active and reliable, you can move to a once-weekly feeding schedule by refrigerating it, or keep it at room temperature and feed daily. Both work indefinitely.
The ones that keep coming up.
How do I know if my starter is alive or dead?
An active starter smells sour, shows bubbles throughout (not just on top), and rises noticeably within 8 hours of feeding. A dead starter shows no bubbles after a week and may develop mold (white, green, or orange patches on the surface—discard it). A sluggish starter just needs more time or warmer conditions.
Can I use tap water?
Yes, unless it's heavily chlorinated. If you're unsure, let tap water sit uncovered overnight to let the chlorine evaporate, or use filtered water. Chlorine inhibits fermentation, so it slows the process.
What if my starter develops mold?
Throw it out and start over. Mold (visible colored patches) means contamination. A dark, unpleasant smell or a thin layer of hooch (alcohol) are fine—these are normal fermentation.
Can I store my starter in the fridge?
Yes. Once it's active, feed it, let it rest for an hour at room temperature, then refrigerate. Feed it once a week. It'll stay alive for months. Before baking, remove it, feed it, wait 8 hours at room temperature, feed again, and use it when bubbly.
My starter is slow. What should I do?
Keep feeding it once daily. The culture is building; yeast and bacteria populations are still small. Warmer kitchens (70–75°F) speed it up. Colder ones (below 65°F) take longer. Some starters are just naturally slower. Patience is the only real fix.
How do I know when it's ready to bake with?
When it reliably doubles in size within 6 to 8 hours of feeding and passes the float test (a spoonful floats in water), it's ready. Some bakers wait until it's quadrupled; that's even safer but takes longer.