How to make sourdough starter from scratch, day by day

Here's how to make sourdough starter: mix 50 g of whole rye flour with 50 g of warm water, then feed the jar those same amounts every day at the same hour. Most starters are bread-ready in 10 to 14 days. The bubbles on day 3 aren't the yeast you're waiting for.

What is a sourdough starter

A starter is a stable culture of wild yeast and lactic acid bacteria living in flour and water. The bacteria make lactic and acetic acid, which pulls the pH down toward 3.5–4.5 and shuts out anything that can't tolerate it. The yeast makes the carbon dioxide that lifts a loaf. Neither is present in useful numbers when you first stir flour into water.

Building one isn't about catching yeast from the air. It's a selection process: a feeding schedule that starves the opportunists already sitting on the flour and rewards the acid-tolerant organisms that do the real work. The first week looks like failure because most of it is failure — just not yours.

What you need before day 1

• Whole rye or whole wheat flour to establish the culture; white bread flour to maintain it later
• A digital scale — cup measurements let the flour-to-water ratio drift within days
• A clear, straight-sided jar around 1 quart (1 L), lid resting on top rather than sealed
• Water at 80–85°F (27–29°C), never hotter than about 90°F
• A spot that holds 75–82°F (24–28°C)

Put a rubber band around the jar at the fill line after every feed. Rise height against that band is the simplest way to track what's actually happening day to day.

How to make sourdough starter from scratch, day by day

Feed at the same time each day. Everything is by weight, and the working ratio is 1:1:1 — equal parts existing starter, flour, and water. Discard down to 50 g before each feed.

Day	Feed	What you see	What's actually happening
1	50 g whole rye + 50 g water	Nothing	Flour hydrates; enzymes start releasing sugars
2–3	50 g starter + 50 g flour + 50 g water, once daily	Fast, coarse bubbling; doubling; cheesy or solvent smell	Leuconostoc and friends bloom at near-neutral pH — the false rise
4–6	Same, once daily	Flat, slack, gray, no activity	Acidity has killed the day-3 crowd; nothing has replaced it yet
7–9	Same, twice daily, 12 hours apart	Fine even bubbles; a slow, domed rise	Acid-tolerant lactobacilli establish; wild yeast multiplies
10–14	1:2:2 or 1:5:5, twice daily	Predictable doubling in 4–8 hours; yogurt-and-fruit smell	Yeast and bacteria settle into a stable ratio

Days 1–3: the false rise

Day 1 is 50 g whole rye and 50 g water stirred to a thick paste. Nothing visible happens for 12 to 24 hours.

Then, usually late on day 2 or during day 3, the jar erupts: big irregular bubbles, a rise that can double or triple, and a smell people describe as parmesan, kimchi, or nail polish remover. This looks exactly like success. It isn't. The gas comes from Leuconostoc and other fast bacteria already on the flour, which thrive at the near-neutral pH of a fresh mix, produce plenty of CO₂ and almost no leavening power, and are about to acidify themselves out of existence.

To skip the stage, use unsweetened pineapple juice in place of water for the first two or three days. It acidifies the mix from the start and suppresses the bloom, so the jar stays quiet early and often runs more consistently through the middle of the timeline.

Days 4–6: the stall

This is where most starters get thrown out. The bubbles stop. The paste goes slack and gray, sometimes with a thin layer of dark liquid on top, smelling faintly sour or of wet cardboard, and it does nothing for two or three days straight.

Nothing is wrong. The acid from the bloom has pushed the pH below what those bacteria survive, and the organisms replacing them build numbers slowly. Keep feeding once a day, on schedule, at the same ratio. A starter left unfed through the stall genuinely can fail; one fed on time almost never does.

Days 7–14: real fermentation

Around day 7 the bubbles change character. Instead of a few large voids you get a fine, even foam through the whole mass, and a dome on top rather than a flat crater. The smell turns yogurt-like, then fruity — apple, or something close to beer.

Move to twice-daily feeding, 12 hours apart, once you see this. Around day 10, switch to a larger ratio — 1:2:2 or 1:5:5 — so acid can't accumulate faster than the yeast works. A starter that still doubles on time at 1:5:5 is far stronger than one that only manages it at 1:1:1.

The best flour for sourdough starter

Whole rye establishes a culture fastest: more yeast and bacteria on the bran, more minerals, and much higher amylase activity, so sugars release quickly. Whole wheat is close behind. Unbleached all-purpose or bread flour works, but expect a slower, flatter first two weeks. Bleached flour is worth avoiding — the chemical treatment strips out a good deal of what the culture feeds on.

Once the starter is established, most bakers move to white bread flour, or a blend like 80% white and 20% whole rye. White ferments more predictably, tastes milder, and makes rise height easier to read.

Water and temperature

Temperature sets your timeline more than anything else. At 75–82°F (24–28°C), 10 to 14 days is typical. At 68°F (20°C) the same starter may need three weeks. Below about 65°F (18°C) you'll see very little, and cold reads as death.

Spots that hold heat: on top of the refrigerator, in an oven with only the light on (check it — some run past 100°F/38°C that way, which is too warm), or a proofing box at 78°F (26°C). Water above roughly 110°F (43°C) begins damaging yeast and kills it near 130–140°F (54–60°C), so hot tap water is a real risk. Ordinary chlorinated tap water is fine; if your utility uses chloramine, which doesn't off-gas overnight the way chlorine does, filter it or use bottled water.

Bubbly is not the same as strong enough to bake

The day-3 bloom and a healthy day-8 rise can look identical in a photo. What separates them is timing and repeatability. Call the starter ready when all of this holds over three consecutive feeds:

• It at least doubles within 4 to 8 hours of feeding at 75–80°F
• The timing is predictable — you can guess peak within an hour
• It domes and holds the dome instead of rising and collapsing
• The interior is webbed with fine bubbles all the way down, not just at the top
• It smells tangy and fruity, not sharply of acetone or glue

The float test is a rough check, not proof. A gassy but weak starter floats, and a stiff starter that's perfectly strong often won't.

Since timing is the tell, write down the feed time and rise height at each check rather than trusting how the jar looked. A notebook does it; so does Sourdough Tracker, a sourdough baking companion app for iPhone.

Three reasons a starter actually dies in week one

Heat. Yeast takes damage above roughly 110°F (43°C) and dies near 130–140°F (54–60°C). Hot tap water and an oven that runs warmer than assumed are the usual culprits.

Starvation. At 100% hydration in a warm kitchen, a culture can exhaust its food in well under 24 hours. Miss several feeds and the pH crashes, hooch pools on top, and activity flatlines. Two or three days of 1:5:5 feeding usually revives it — not always.

Mold. Fuzzy spots in pink, orange, green, or black mean the batch is gone — discard it rather than scraping around it. Dried starter crusted on the jar wall is the usual source, so wipe the sides and change jars every few days. Hooch, the gray-brown liquid that separates on top, is alcohol rather than mold and stirs right back in.

The far more common outcome isn't death at all. It's someone giving up on day 5, mid-stall, on a starter two days from working.

FAQ

How long does it take to make a sourdough starter?

Ten to 14 days in a kitchen at 75–82°F (24–28°C). A cool 68°F kitchen can stretch it to three weeks; a warm one occasionally gets there in 7 or 8 days. It's ready when it doubles predictably within 4 to 8 hours of feeding, not when the calendar says so.

Why did my starter bubble on day 3 and then stop?

That's the normal sequence. Day-3 gas comes from bacteria that can't survive the acidity they create, and the yeast replacing them needs several more days to build numbers. Keep feeding on schedule through days 4 to 6 and activity returns.

Do I have to discard sourdough starter?

While you're building it, yes. Discarding keeps the ratio of fresh flour to old culture high, so the yeast has food and acid doesn't accumulate — and without it you'd need absurd quantities of flour to hold a 1:1:1 feed. Once established, keep as little as 20–30 g and the discard shrinks to almost nothing.

What's the best flour for a sourdough starter?

Whole rye to establish, white bread flour to maintain. Rye's enzyme and mineral content moves a new culture along several days faster, and white flour gives cleaner flavor and a more readable rise once things are stable.