Building a Sourdough Starter from Scratch
A starter is not something you make once and forget. It's a thing you keep alive, feed regularly, and come to depend on. The first week is about building enough microbial activity that you can see and smell the fermentation. After that, it becomes a rhythm—a twice-daily feeding if you keep it on the counter, or a weekly one if you refrigerate it.
What you're actually doing
You're creating an environment where wild yeast and lactic acid bacteria naturally colonize a flour-and-water mixture. There's no magic ingredient—just consistency and time. The flour contains dormant spores; water activates them. Your job is to feed the culture regularly so it outcompetes any unwanted microbes and grows strong.
- A clean glass jar or container (at least 1 quart / 1 liter)
- A kitchen scale (optional but useful for consistency)
- A spoon or small whisk
- A kitchen towel or cloth
What goes in.
- 50 gwhole wheat flour or rye flour (for day 1 only)
- 50 gfiltered or dechlorinated water (for day 1 only)
- 25–50 g per dayall-purpose or bread flour (days 2 onward)
- 25–50 g per dayfiltered or dechlorinated water (days 2 onward)
Feed consistently, watch for activity
A sourdough starter thrives on routine. Feed it at the same time each day, always discarding some of the old culture before adding fresh flour and water. This keeps the ratio of food to microbes balanced. You're looking for bubbles, a risen dome, and a pleasant sour smell—these are signs the yeast and bacteria are doing their job.
The method.
Day 1: Make the initial mixture
In a clean jar, combine 50 g whole wheat or rye flour and 50 g filtered water. Stir well until no dry flour remains. The flour should be completely hydrated. Cover the jar loosely with a cloth or place a loose lid on top—you want air exchange, not a sealed container. Leave it at room temperature (68–75°F / 20–24°C is ideal, but anywhere between 65–80°F works).
Days 2–3: Check for activity, then feed
By day 2 or 3, you may see some bubbles and smell a slightly sour or yeasty aroma. This is normal fermentation beginning. Discard about half the mixture (roughly 50 g). Add 25–50 g fresh all-purpose or bread flour and 25–50 g water. Stir until smooth. Cover loosely again. Return to room temperature.
Days 4–5: Establish a feeding schedule
Continue the same pattern once daily: discard half, feed with equal parts flour and water by weight (25–50 g of each). You should see more vigorous bubbling and a stronger sour smell. The starter may rise and fall between feedings—this is the yeast eating and producing gas. If you see a brown liquid (hooch) on top, it means the bacteria are hungry; stir it back in or pour it off, depending on preference.
Days 6–7: Look for predictable doubling
By now, the starter should be noticeably bubbly, with a pleasant sour aroma. The real test: feed it in the morning and watch whether it roughly doubles by evening (or within 4–8 hours). If it does, and if it rises and falls consistently with each feeding, your starter is ready to use in bread.
Transition to maintenance
Once your starter is active and predictable, you can move it to the refrigerator and feed it once a week, or keep it on the counter and feed it twice a day. If refrigerating, feed it, let it sit at room temperature for 30 minutes to 1 hour, then seal it loosely and place it in the fridge. Before baking, take it out, feed it, and let it rise until bubbly and nearly doubled—usually 4–12 hours depending on how cold it was.
Other turns to take.
Faster start with whole grain flour
Whole wheat, rye, or spelt flour ferment faster than white flour because they contain more nutrients and microbes. Start with one of these for days 1–3, then switch to all-purpose. You may see activity by day 2 instead of day 3.
Warmer environment for speed
If your kitchen is cool, place the jar in a turned-off oven with the light on, or near (not on) a radiator. A warmer starter ferments faster—you might have a usable culture in 4–5 days instead of 7.
Using bottled or boiled water
Chlorine in tap water can slow fermentation. If your tap water is heavily chlorinated, use filtered water or let tap water sit uncovered for 24 hours to off-gas the chlorine. Boiled water works if cooled first.
When it doesn't go to plan.
Don't throw away your daily discards once the starter is established—save them for pancakes, crackers, or discard responsibly rather than down the drain.
A white or gray liquid layer (hooch) that forms on top is harmless alcohol produced by yeast. Stir it back in for extra flavor, or pour it off if you prefer a milder taste.
If your starter smells bad (like acetone or paint) rather than pleasantly sour, it may have mold or an unwanted infection. Start over. True mold is fuzzy or visibly colored; a thin yeast layer on top is normal.
Consistency matters more than precision. Whether you feed 25 g or 50 g of flour, the culture will eventually become active. Smaller feedings train it to ferment faster.
Your starter's timing depends on temperature and the flour you use. A cool starter may take 12 hours to rise; a warm one, 4. Neither is wrong—just plan your baking accordingly.
The ones that keep coming up.
How do I know my starter is ready to bake with?
It should rise noticeably (at least 50%, ideally double) within 4–12 hours of feeding, smell pleasant and sour, have visible bubbles throughout, and pass the float test: drop a small spoonful into water. If it floats, the yeast is producing enough gas. If it sinks, wait another day or two.
What if my starter isn't showing bubbles by day 3?
This is normal. Cold kitchens ferment slowly. Move it to a warmer spot, or simply continue feeding once daily. Some starters take 10 days to become visibly active. Patience and consistency matter more than speed.
Can I use tap water?
Yes, unless your water is heavily chlorinated. If fermentation seems slow, try filtered or dechlorinated water. Boiled and cooled water also works.
Should I use all-purpose or bread flour?
Either works. Bread flour has more protein, which some say creates a slightly stronger culture, but the difference is minimal. Use what you have. Avoid cake flour, which is too soft.
Can I refrigerate my starter if it's not fully active yet?
Not recommended. Refrigeration slows fermentation dramatically. Finish your 5–7 days at room temperature first. Once it reliably doubles when fed, then you can refrigerate it for long-term storage.
How long does a sourdough starter last?
Indefinitely, if fed regularly. Starters more than 100 years old exist and are still baking bread. The yeast and bacteria are self-sustaining as long as you feed them.