Mixing equal weights of flour and water at room temperature wakes dormant wild yeast and lactobacilli, which ferment the slurry into a bubbly, living starter over five to seven days. Feed that starter until it reliably doubles, autolyse fresh flour with water, add salt, build structure through stretch-and-folds, bulk-ferment, shape, cold-retard overnight, and bake in a preheated Dutch oven at 230 to 250°C until the crumb reaches 96 to 98°C internally.
What follows walks you through the microbiology behind the rise, the first two weeks of starter life, mixing and shaping cues, the Dutch-oven bake, and a troubleshooting matrix for the bakes that flop. You will know how to spot a healthy starter, when bulk fermentation is actually done, and how to read a finished loaf without slicing it open.
The Living Culture That Makes Sourdough Different
Supermarket loaves rise from a single organism: a domesticated strain of Saccharomyces cerevisiae chosen for speed and mild flavor. Sourdough, by contrast, ferments through a mixed community of wild yeasts (often Kazachstania and Candida species in the early weeks, with Saccharomyces arriving later from your flour and hands) working alongside lactic-acid bacteria like Lactobacillus sanfranciscensis. The yeasts produce most of the carbon dioxide that lifts the dough; the bacteria produce organic acids that give the crumb its tang.
That two-organism partnership is what separates a sourdough crumb from a yeasted one. Fast commercial yeast ferments sugars in two or three hours and leaves little flavor behind; the lactic acid bacteria in a sourdough culture run for 8 to 24 hours, producing lactic and acetic acid, breaking down proteins into amino acids, and creating the browning precursors that build a deeply caramelized crust.
A 2020 study in mSystems comparing industrial and sourdough fermentations of the same flour found the sourdough loaves had nearly twice the free amino acid content, which contributes directly to browning and savory flavor.
Temperature, hydration, and time are the three knobs you actually control. Almost every sourdough problem traces back to one of them being set too high, too low, or for too long.
The acids do more than flavor the loaf. They lower the pH of the dough into a range of roughly 3.8 to 4.6, where many gluten proteins begin to break down into smaller peptides, which is why a long-fermented sourdough often feels easier to digest than a yeasted bread made from the same flour.
The same acids slow starch digestion by inhibiting amylase, an effect linked in several small studies to flatter post-meal blood glucose responses compared with commercial white bread.
Whole-grain and rye flours ferment faster than all-purpose because they carry more wild yeast and bacteria, plus more minerals and broken starch for those microbes to feed on. A starter built on whole-wheat rye typically doubles within four hours at 24°C, while one built on all-purpose can take eight hours to peak at the same temperature.
That difference is why most guides recommend starting with at least 50% whole-grain flour, then transitioning to lighter blends once the culture is stable.
Why the Wild-Yeast-and-Bacteria Balance Shapes Flavor
Lactic acid gives a clean, yogurt-like brightness. Acetic acid gives a sharper, vinegar-like edge, and it develops more when fermentation runs warm or when the dough is wetter. A loaf built from a bacterial-leaning culture (older, more acidic, fed with whole-grain flour) tastes tangier; a yeast-leaning culture (younger, fed with white flour, kept cooler) tastes milder and rises faster.
Most home bakers end up somewhere between those poles, and you can nudge your culture toward either side by adjusting temperature, hydration, and feed flour.
That nudge is easiest when you begin with a starter built on reliable ratios rather than guesswork.
Building a Starter That Actually Rises
Day 1, mix 50 grams of whole-wheat or rye flour with 50 grams of room-temperature water in a clean jar, stir until no dry clumps remain, and loosely cover it. Day 2, you may see a few bubbles, but probably not much rise. That flat, slightly sour-smelling phase is normal; the wild microbes are still establishing themselves, and competing bacteria often produce off odors (cabbage, acetone, gym socks) before the right yeasts take over.
Most guides skip this stage because it can feel discouraging, but the smell almost always passes by day 4 or 5.
Day 3 through day 7, begin a daily discard-and-feed cycle. Stir down the starter, scoop out all but about 25 grams, then add 25 grams of flour and 25 grams of water. Aim for a 1:1:1 ratio by weight (starter:flour:water). Keep the jar around 24 to 26°C, loosely covered so CO2 can escape.
By day 5 to 7, a healthy starter should roughly double within 4 to 8 hours after a feed and show a domed, glossy top dotted with bubbles.
Do not throw out the discard. Pancakes, crackers, waffles, and pizza dough all work fine with unfed starter. Storing discard in a separate jar in the fridge turns it into a free ingredient.
Day 7 to 14 is the transition. Once your starter reliably doubles, shift the feed ratio from heavy whole-grain toward the flour you plan to bake with. A practical approach: drop whole-grain from 100% to 50%, then 25%, then 0% across four to five days. By day 14, your starter should peak within 4 to 6 hours at 24°C on a 1:1:1 white-flour feed, and you are ready to bake.
Reviving a Neglected or Sluggish Starter
If your starter sits unfed in the fridge for weeks and arrives at a brown liquid layer (called hooch) on top of a sunken mass, do not throw it out. Pour off the hooch, scoop out 25 grams of the solid starter underneath, and feed it 25 grams flour and 25 grams water at room temperature. Repeat twice at 12-hour intervals. The yeast usually revives in 24 to 48 hours.
If the starter smells truly rotten (like garbage or rotting meat) or turns pink, moldy, or orange, that signals contamination; discard it and start over.
Visual Cues for a Healthy Starter
A mature starter ready to leaven a loaf should rise to roughly twice its volume 4 to 6 hours after a 1:1:1 feed at 24°C, hold a domed top without collapsing for an hour or two, then slowly fall. If it rises fast and immediately collapses, it is hungry and underfed. If it barely moves at all, the wild-yeast population is thin or the temperature is too cold.
Both conditions respond to warmer feeding temperatures of 26 to 28°C and more frequent flour changes.
Reading the Dough: Hydration, Autolyse, and Bulk Fermentation
Once your starter reliably doubles, the real work begins. The classic Tartine Country Loaf formula starts with 1000 grams white flour, 700 grams water, 200 grams mature starter, and 20 grams salt. That ratio gives 75% hydration (water weight divided by flour weight), which sits in the middle of the home-baker range: wetter than a sandwich loaf, drier than an open-crumb ciabatta.
Hydration changes how the dough feels in your hands and how the crumb turns out. Lower hydration around 65% produces a stiffer, easier-to-shape dough with a tighter crumb. Higher hydration around 85% produces a slack, sticky dough that yields a more open, glossy crumb but demands a confident hand and a longer, gentler bulk to build structure. For a first loaf, 70 to 75% hydration stays forgiving and produces a classic chewy-but-open result.
| Hydration | How It Feels | Crumb Outcome |
|---|---|---|
| 65% | Stiff, almost clay-like; holds shape without a bench scraper | Even, tight, sandwich-style |
| 75% | Soft, tacky, slightly sticky when poked; flows slowly when shaken | Open with smaller, evenly distributed holes |
| 85% | Slack, batter-like; flattens under its own weight | Very open, glossy, irregular holes |
Begin with the autolyse: combine 1000 grams flour and 700 grams water in a bowl, stir until no dry pockets remain, and let it rest for 30 to 60 minutes. This step lets the flour hydrate fully and the gluten begin organizing on its own before any salt or starter enters. Salt tightens the gluten and slows fermentation, so adding it first would fight the autolyse.
After the rest, mix in 200 grams of peaked starter and 20 grams of salt until the dough comes together, then let it sit for another 20 minutes before the first stretch-and-fold.
The Stretch-and-Fold Sequence That Replaces Kneading
Over the next three to four hours, perform four sets of stretch-and-folds at 30-minute intervals. With a wet hand, lift one corner of the dough, stretch it up until you feel resistance, fold it over to the opposite side, and rotate the bowl a quarter turn. Repeat four times per set. The dough should feel noticeably stronger and more elastic by the second set and hold its shape by the third.
By the fourth set, it should pass a windowpane test: a small piece stretched thin lets light through without tearing.
When Bulk Fermentation Is Actually Done
Bulk fermentation usually takes 4 to 5 hours at 24 to 26°C, but temperature and starter strength can stretch that to 8 hours or compress it to 3. Forget the clock and watch the dough. Look for a 50 to 75% rise in volume, jiggly edges when you shake the bowl, and bubbles clustering along the sides and across the top.
A poked indent should fill in slowly over a few seconds rather than springing back immediately (under-proofed) or staying open like a crater (over-proofed). When you see those cues, move straight to pre-shaping.
Those proofing cues become trustworthy only once you understand what hydration, autolyse, and bulk fermentation are doing beneath the surface.
Shaping, Cold Retard, and the Dutch Oven Finish
Turn the dough out onto a lightly floured counter and divide it gently, leaving the surface skin intact. Pre-shape into a loose round, let it rest 20 to 30 minutes until the gluten relaxes, then final-shape into a tight boule or batard by folding the edges into the center and rolling the dough away from you on an unfloured counter to build surface tension.
A taut skin matters more than the type of banneton; a wicker basket lined with a floured cloth, a plastic bowl with a tea towel inside, even a colander will all work as long as the dough can hold its shape.
Place the shaped loaf seam-side up in a banneton dusted with rice flour (rice flour resists sticking better than wheat flour), cover it, and refrigerate at 3 to 5°C for 8 to 16 hours. The cold retard slows fermentation almost to a halt while the bacteria keep producing flavor acids and the gluten firms up, which makes scoring clean lines much easier.
Twelve to fourteen hours gives the best flavor for a 75% hydration white-flour loaf; going past 18 hours risks over-proofing unless the starter was young or the dough was stiff.
Scoring Patterns That Direct Oven Spring
A single bold slash down the center, about a half-inch deep and curving slightly, gives a classic ear. A crosshatch of three or four parallel cuts produces a more rustic, blooming look. Hold the blade nearly parallel to the surface and cut with confidence in one motion; hesitation tears the skin. A sharp lame (a curved razor designed for scoring) or a clean utility-blade knife works better than a kitchen knife.
The Dutch Oven as a Steam Chamber
About 45 minutes before baking, place a Dutch oven (lid on) on the middle rack and preheat to 245°C. The trapped steam inside the closed pot is what gives a sourdough loaf its glossy, blistered crust and its first burst of oven spring. Lower the dough in on a piece of parchment paper, slash it if you have not already, cover, and bake for 20 minutes.
After 20 minutes, remove the lid to release steam and drop the temperature to 230°C. Bake another 20 to 25 minutes, until the crust is deeply browned and an instant-read thermometer reads 96 to 98°C at the center.
A 2018 study in the International Journal of Gastronomy and Food Science measured crust thickness and found enclosed-pot baking produced crusts roughly 40% thicker than open-tray baking at the same oven temperature. That thickness is what gives a sourdough loaf its crackle when you tap it.
Signals That the Loaf Is Fully Baked
Color, internal temperature, and sound all matter. The crust should reach a deep caramel brown, not golden. The bottom, when you lift the loaf out of the pot, should sound hollow when you knock on it. Most importantly, the internal crumb should hit 96 to 98°C; below that, starches have not fully gelatinized and the crumb will be gummy.
Pull the loaf out and cool it on a wire rack for at least one hour before slicing; cutting too early traps steam and ruins the structure.
Diagnosing What Went Wrong Before You Bake Again
Most sourdough failures come down to proofing, hydration, or fermentation temperature. The matrix below maps the most common symptoms to their usual causes. Use it the morning after a flat loaf to figure out which lever to adjust next time.
| Symptom | Likely Cause | Fix for the Next Bake |
|---|---|---|
| Flat loaf with no oven spring | Over-proofed bulk or final proof, or starter was past its peak when added | Shorten bulk by 30 to 60 minutes; feed starter so it peaks right as you mix the dough |
| Dense, gummy crumb | Under-baked (interior below 96°C) or under-fermented | Bake to 98°C internal; extend bulk by 30 minutes at 24°C |
| Pale, soft crust | Oven not hot enough, or lid removed too early | Raise bake temp to 250°C and keep the lid on for the full 20 minutes |
| Starter that will not rise | Too cold, too young, or being fed with chlorinated tap water | Use filtered water, keep starter at 26 to 28°C, and feed twice a day for a week |
| Sour smell but no rise | Bacterial dominance outpacing yeast; starter acidic and hungry | Discard and feed twice at 8-hour intervals with fresh flour to reset the balance |
| Tear marks along the bottom | Under-proofed, or shaped with weak surface tension | Extend bulk, build more tension during final shaping |
| Heavy, doughy top with a tight bottom | Stretched too thin during shaping, or scored too shallow | Handle the dough more gently; cut at least half an inch deep at a 30° angle |
Reading the Dough One Last Time Before the Oven
Just before loading the shaped loaf, poke the cold dough gently with a floured finger. The indent should slowly spring back halfway, leaving a faint mark. If it snaps back fast and fills in, the loaf is under-proofed; let it sit at room temperature for another 30 to 60 minutes before baking.
If the indent stays open and the dough feels slack and airy, it is over-proofed and will not rise much in the oven; bake it anyway and adjust timing on the next one.
A failed loaf still teaches you something, and the notes you keep now shape every bake that follows.
Storing, Slicing, and Keeping the Starter Alive Between Bakes
Once your starter reliably peaks, you have three storage options depending on how often you bake. Bakers who bake weekly can keep the starter on the counter and feed it once a day at room temperature. Bakers who bake every two to four weeks should store it in the fridge, feed it weekly, and pull it out the night before baking to bring it back to peak.
Bakers who bake rarely can dry a thin layer of starter on parchment, crumble it into a jar, and rehydrate it months later with flour and water over a day or two.
For the loaf itself, slice only after the crumb has cooled to room temperature, which usually takes one to two hours. Cutting too early traps steam and turns the crumb gummy. Once sliced, store the loaf cut-side down on a wooden board, loosely covered with a tea towel, and consume within 48 hours.
The crust softens as moisture migrates from crumb to crust, which is part of why day-two sourdough carries a different texture than day-one; some bakers prefer that, others do not.
For longer storage, wrap a fully cooled loaf tightly in plastic and freeze it. Thaw at room temperature and refresh the crust in a 200°C oven for 5 to 8 minutes. Frozen sourdough keeps its flavor for two to three months with almost no quality loss.
Build a simple weekly rhythm so the starter peaks when you are ready to mix. If you plan to bake Saturday morning, feed the starter Thursday evening (about 60 hours before baking) so it goes through a full rise and fall cycle, then feed it again Friday afternoon. By Saturday morning it should be at peak and ready to mix. Refrigerator storage between bakes is the easiest way to make this predictable without daily feedings.
How Crumb Structure Continues to Set After Baking
Starch retrogradation continues for 12 to 24 hours after a loaf leaves the oven. That is why a freshly cut slice often feels softer and more pliable than one cut the next morning. The flavor also opens up as volatile acids dissipate and Maillard reaction products finish developing. Plan your tasting for a slice cut at least an hour after baking, and ideally the next day, before judging whether a recipe needs adjustment.
The Bottom Line
Successful sourdough depends less on following any single recipe and more on reading the dough in real time. When you understand that temperature, hydration, and time are the only real levers, every other choice, from flour blend to scoring pattern, becomes a tool you can adjust on the next bake.
Build a starter you trust, learn the cues for a finished bulk ferment, and trust the thermometer over the clock; the loaf on the cooling rack will tell you what the next one should do differently.
FAQ
How long does it take to make sourdough bread from scratch?
From the moment you mix flour and water for a new starter to the moment you cut into your first loaf, allow 14 to 21 days. A stable starter typically takes 7 to 14 days of daily feeding, and the bake itself takes another 24 to 36 hours once you are mixing dough, including a 12-hour cold retard overnight.
Do you need a Dutch oven to bake sourdough?
A Dutch oven is the most beginner-friendly way to trap steam, but it is not the only way. A pizza stone with a metal bowl or inverted sheet pan covering the loaf during the first 20 minutes produces similar oven spring and crust blistering. For a third option, a lidded cast-iron skillet or a Challenger Bread Pan is purpose-built for the same effect.
How do you make a sourdough starter at home?
Mix 50 grams of whole-wheat or rye flour with 50 grams of room-temperature, non-chlorinated water in a clean jar. Cover loosely and leave it at 24 to 26°C for 24 hours. Then once a day, discard all but 25 grams of the mixture and feed it 25 grams flour and 25 grams water. By day 7 to 14, a healthy starter should roughly double in volume within 4 to 6 hours after a feed.
Why is my sourdough bread dense and gummy inside?
The two most common causes are an under-baked interior and an under-fermented dough. Pull the loaf when an instant-read thermometer reads 96 to 98°C at the center. If the temperature is fine but the crumb still feels tight, extend bulk fermentation by 30 to 60 minutes at 24°C and check that your starter was at peak when you mixed the dough.
How long should sourdough bulk ferment?
At 24 to 26°C with a mature starter, expect 4 to 5 hours, though warmer kitchens shorten that to 3 hours and cooler kitchens stretch it to 7 or 8. Watch for a 50 to 75% rise, jiggly edges, and bubbles along the side of the bowl. A poked indent should fill in slowly over a few seconds before you move to shaping.
Can I use all-purpose flour to make sourdough bread?
Yes. An all-purpose flour produces a mild-flavored, classic-textured loaf. All-purpose works especially well after you have built the starter on a whole-grain base for the first 7 to 10 days, then transitioned to all-purpose feeds. Whole-grain loaves rise faster and carry a deeper, nuttier flavor, so pick whichever matches the bread you want to eat.
