Sourdough Baking Complete Guide

This deck walks you through the fundamentals of sourdough baking, from nurturing your very first starter all the way to shaping and proofing your loaf. The cards cover core concepts like hydration, autolyse, bulk fermentation, cold retard, and various folding techniques, so you can build a solid mental map of the whole process rather than just memorizing isolated steps.

It's a great fit if you're a beginner who wants to understand the "why" behind sourdough, or an intermediate baker looking to firm up the vocabulary and science behind techniques you may already be using. Each card targets a single concept or term, making it easy to spot the gaps in your knowledge and revisit tricky ideas like the difference between proofing and bulk fermentation.

To get the most out of your study sessions, try reviewing a small batch of cards daily rather than cramming everything at once, and pay special attention to terms that connect to one another, such as hydration, folding methods, and fermentation timing. Connecting these ideas in your mind will make troubleshooting your bakes much easier down the road.

A sourdough starter is a living culture of wild yeasts and lactobacilli, maintained with regular flour-and-water feedings. It serves as the sole leavening agent in true sourdough bread, producing both rise and the characteristic tang. For active use, a typical feeding ratio is one part starter to five parts flour and five parts water by weight, which produces a slow, full peak roughly eight to twelve hours after feeding at around 24°C. A starter is ready to bake with when it at least doubles within four to eight hours of feeding, smells fruity or yogurty rather than vinegary, and passes the float test — though a thick starter can float even when under-active, so rise speed and smell remain more reliable. The peak of a starter's rise is the highest point just before it begins to fall; it is at peak or just past peak, "ripe," that the starter is best incorporated into dough for predictable fermentation. For a 1:5:5 feeding, the starter can still be used one to two hours past peak, but longer and the gluten begins to weaken; refrigerating overnight after peak is a common way to hold it for next-day use.

A healthy starter smells yeasty, fruity, slightly tangy, and yogurty. A dark watery layer on top, called hooch, indicates the starter is hungry — it can be stirred back in, followed by a fresh feeding, or poured off if very old. A vinegar or nail-polish smell points to over-acidity or contamination and calls for repeated feedings to reset the culture. To build a starter from scratch, mix 50 grams of whole rye flour with 50 grams of water in a jar, rest it for 24 hours, then discard half and feed it 1:1:1 daily; active bubbles usually appear between day three and day seven. Whole rye is preferred for new starters because it carries more wild microbes and nutrients than all-purpose flour. A young starter, only hours past feeding, gives mild CO₂ production with less acid, while a mature starter aged six to twelve hours at room temperature reaches peak activity with a balanced acid profile. Ideal ambient temperature for an active starter is 24–26°C; warmer conditions speed fermentation and increase acidity, cooler conditions slow it and yield milder flavor.

For storage, a starter kept at room temperature in a sealed jar will last a few days between feedings, while long-term storage is best in the fridge at a 1:5:5 ratio refreshed weekly. For multi-month storage, the starter can be dehydrated by spreading it thin on parchment until dry, then crumbled and stored in a jar — rehydration with fresh water and flour brings it back when needed, a useful travel-proofing method. Freezing also works well: feed the starter strong, let it reach peak, then freeze in small portions like ice cube trays, thawing and feeding twice before use. To refresh a neglected starter, discard most of it and feed 1:2:2 every 12 hours at room temperature; within two to three days it should be active again, signaled by a sweet fruity smell. Starter discard need not go to waste — it enriches pancakes, waffles, crackers, pizza dough, banana bread, fried discard crackers, or any dough as a small flavor-boosting pre-ferment, though discard is less active than ripe starter and is not strong enough to leaven bread on its own.

Hydration is the single most important numerical concept in sourdough — it is the weight of water expressed as a percentage of flour weight, so 75 percent hydration means 750 grams of water per 1,000 grams of flour. Beginners should target 65–72 percent hydration with bread flour, which is easier to handle while still allowing an open crumb. Advanced bakers pushing for very open, holey crumb often work at 75–85 percent hydration, but only with strong flour and a confident handling technique. Hydration must be raised by roughly 3–5 percent for every 10 percent of whole-wheat flour substituted, since whole grains absorb more water. Beginners seeking lighter crumb in whole-wheat doughs can sift out about 20 percent of the coarse bran and reincorporate the rest, reducing fiber intensity while preserving flavor.

Flour choice shapes everything about a loaf. Bread flour, with 12–14 percent protein, develops stronger gluten and holds high hydration better than all-purpose flour at 10–12 percent, which gives a tighter crumb. Whole rye and whole wheat carry more minerals and microbes, producing more lactic and acetic acid and therefore tangier bread, while white bread flour yields milder, sweeter flavors. High-extraction flour, milled between whole grain and white, retains around 70–85 percent of the bran for flavor and nutrition with better gluten performance than 100 percent whole wheat. For beginners chasing open crumb, a strong bread flour with at least 20 percent whole grain or high-extraction flour is a sweet spot. Italian Type 00 flour is finely milled and often around 11 percent protein, excellent for pizza but less suited to tall sourdough loaves. Spelt has weak gluten and a nutty flavor and is best used at 30 percent or less; rye is sticky with very high enzyme activity, used at 10–20 percent unless making 100 percent rye — its soluble fiber gels and traps gas, producing a more uniform but denser crumb with deep malty flavor. Vital wheat gluten concentrate can be added at 1–2 percent of flour weight to boost strength in whole-grain, weak-flour, or high-inclusion doughs.

Salt's role goes far beyond flavor: it tightens gluten, regulates fermentation, strengthens crust, and slows over-proofing. The standard amount is 1.8–2.2 percent of flour weight — roughly 2 percent as a default, leaning toward 1.8 percent in high-hydration doughs and up to 2.2 percent in tighter ones for flavor balance. Salt should be added after autolyse, once gluten has begun forming — usually 20–40 minutes into bulk — because adding too early inhibits gluten development while adding too late causes uneven mixing. Water also matters: hard water rich in calcium tightens gluten and may slow fermentation, soft water gives a more open crumb but can feel slack, and chlorinated tap water can weaken gluten and disrupt yeast, so letting it sit uncovered for 24 hours or using filtered water is a common fix. Optional additions include diastatic malt powder at 0.5–1 percent of flour weight for extra amylase activity and mild sweetness, and a small amount of sugar or honey to feed yeast in early fermentation for faster rise and softer crumb, useful for beginners though not essential in true sourdough.

The baker's percentage system anchors any sourdough recipe: flour equals 100 percent, and every other ingredient is expressed as a percentage of flour weight. To scale a recipe, simply pick a total flour weight and multiply by each ingredient's percentage — for example, with 800 grams of flour, 75 percent hydration equals 600 grams of water, 2 percent salt equals 16 grams, and 20 percent levain equals 160 grams. The levain-to-flour ratio in the dough is the inoculation rate; Tartine's formula uses a strong 20 percent levain, while other approaches range from 10 percent for slower, more flavorful ferments to 25 percent or more for faster, less sour ones. A higher inoculation rate produces faster bulk fermentation, more open crumb, and less sour flavor, while a lower rate produces longer bulk with deeper, more tangy flavor.

Autolyse comes first: mix only flour and water — no salt, no starter — and rest for 30 minutes to 2 hours. This period hydrates the flour and develops gluten passively, improving extensibility before any fermentation begins. A warm autolyse at room temperature (30–90 minutes) emphasizes enzymatic activity, while a cold autolyse in the fridge (8–24 hours) pushes even more flavor development and extensibility at the cost of slower gluten formation. After autolyse, salt and ripe levain are mixed in, and the dough enters bulk fermentation. During this first rise, most of the dough's flavor and structure develop over 4–8 hours at 24–26°C, ending when the dough shows visible jiggle, a domed top, and roughly 50–70 percent rise. The signature Tartine method runs through autolyse, mix, and a 4–5 hour bulk punctuated by sets of folds. A foundational recipe of 1,000 g bread flour, 750 g water (75 percent), 200 g ripe starter (20 percent), and 20 g salt (2 percent) illustrates the approach.

Dough temperature, often called DDT, is calculated as a weighted sum of flour, water, starter, and ambient temperatures plus a friction factor from mixing, with 26–28°C being the standard baker's target. In winter, warmer water at 30–35°C and a warmed bowl can compensate; in summer, chilled water or cold starter keeps the dough from over-heating. Levain building is its own craft: a levain is a sub-portion of starter freshly built up for one bake, distinct from the mother starter you maintain, while the term "preferment" refers to any portion fermented before final mix including poolish and biga, which use commercial yeast. A single build uses one feeding and is fine when the starter is active; a double build uses two successive feedings and is preferred when the starter is sluggish or fridge-cold. For same-day baking, build the levain 4–6 hours before mix using a 1:5:5 ratio at 24°C so it peaks right when it is needed. Liquid levains at 80–100 percent hydration rise faster with milder lactic-acid flavor, while stiff levains at 50–60 percent hydration rise slower and produce more acetic acid for a sharper tang.

Folds replace hand kneading throughout bulk. Stretch and folds every 30 minutes during the first 2–3 hours strengthen gluten and lightly degas the dough; coil folds, where the dough is lifted from underneath and folds on itself, are gentler and favored for high-hydration doughs; lamination stretches the dough thin on the counter and folds it back up, distributing inclusions like seeds or cheese while aligning gluten. The windowpane test confirms gluten development — stretch a small piece thin, and if light passes through without tearing, gluten is sufficiently developed. "Al dente" gluten tears slightly at the windowpane stage; "fully developed" gluten is very extensible with no tearing, and that full development is what produces open crumb. Dough strength is gluten's ability to hold gas and shape: strong dough feels elastic and holds form, weak dough spreads and tears. Fermentation tolerance is the workable window from end of mix to collapse; a wider tolerance gives more schedule flexibility. To build tolerance, lower inoculation to 10–12 percent, cool the dough to 22–24°C, or pre-shape and refrigerate bulk.

After bulk, the dough is divided and pre-shaped into rough rounds, then given a 20–30 minute bench rest covered so the gluten can relax before final shaping. Shaping aims for taut surface tension without ripping the dough — too gentle leaves a slack loaf that sags flat, too rough tears gluten and leads to a dense crumb. Slack dough that simply will not hold its shape after shaping usually traces to under-developed gluten, a warm environment, over-hydration, weak flour, or excess fermentation; a 20-minute rest followed by coil folds can often rescue it.

The shaped dough then enters final proof, traditionally in a banneton — a proofing basket lined with rice flour that supports the dough and leaves a spiral imprint. Bannetons are typically dusted with a 50/50 rice-and-AP blend or pure rice flour, with excess tapped out, and rice flour specifically is preferred because it does not absorb into the dough during long retards. Bench flour is the everyday flour used to prevent sticking during shaping, often all-purpose, while rice flour is reserved for bannetons so it doesn't incorporate into the dough. For very sticky doughs, a floured cloth liner inside the banneton prevents tearing and gives an even spiral pattern. Banneton sizing matters: 500 grams of flour dough typically needs a 20–22 cm banneton, and a tight banneton produces a taller loaf. Alternatives include a couche (linen cloth folded into ridges, dusted with flour, with batards resting seam-up between folds), a cane brotform, or even a colander lined with a floured tea towel.

Cold retard is where most of sourdough's signature flavor develops. Placing shaped dough in the fridge for 8–24 hours at 4°C slows yeast activity while letting bacteria produce more acid, which adds tang, makes the dough easier to score, and improves crumb. The sweet spot for maximum flavor is 12–18 hours; beyond 24–36 hours, gluten can over-relax and the dough becomes hard to score. Retarding for at least eight hours also helps the surface dry slightly so the ear will curl up cleanly during oven spring. Cold temperatures favor lactic acid (mild, milky tang), while warm bulk fermentation favors acetic acid (sharp, vinegary). For very long flavor development, the cold-shock method refrigerates shaped dough for 24–72 hours and bakes directly from the fridge without warming up, extending the retard window considerably. Bulk itself can be retarded overnight in the fridge for high-inoculation doughs or in warm kitchens where bulk would otherwise race too fast, slowing the yeast while still allowing slow flavor development.

Scoring directs where the dough opens during oven spring; without a score, it splits along its weakest point. The tool of choice is a lame — a razor blade holder with a curved or straight blade — the same tool sometimes called a scoring blade. Some pros snap a double-edge razor in half for ultra-clean cuts. Depth is roughly 5–10 mm at a 30–45° angle; shallow cuts produce little ear, overly deep cuts collapse. A single confident stroke along the long axis, just into the skin of the dough, gives the classic ear — the raised, crispy flap of crust along the score line. To get a bigger ear, the oven should be very hot, steam should be plentiful, the dough slightly under-proofed, the score deep and angled, and the blade very sharp. The "crown" is the ridge along the top of the ear from a deep angled score that lifts cleanly. A cross score, with two perpendicular cuts, opens a boule into four sections for decorative effect rather than maximum spring, while a double cut uses parallel lines to open the loaf wider, often used on batards. Over-scoring — too many cuts — opens the loaf in many places without producing a single defined ear, so one confident cut always beats five hesitant ones. For very wet dough that drags, dipping the lame in water or lightly spraying the dough's surface prevents tearing.

A Dutch oven is the most reliable tool for home sourdough baking because it traps steam released from the dough itself during the first 20 minutes of baking. Preheat the Dutch oven to 260°C, bake covered at 245°C for 20 minutes, then uncover and drop to 230°C for another 20–25 minutes. Parchment paper between the dough and the Dutch oven makes transferring quick and safe and prevents sticking. A baking steel transfers heat faster than a baking stone and yields better oven spring, while a stone gives more even radiant heat at lower cost. Without a Dutch oven, a baking stone plus a steam tray (lava rocks, a metal pan of hot water, or ice cubes) or a covered roaster all work. Baking on a tray without steam is possible if the loaf is sprayed with water before loading and a pan of boiling water sits on the rack below, though results vary. The initial oven temperature is sometimes called the firing temperature.

Steam phase management is critical: keeping the surface pliable for the first 15–20 minutes allows maximum oven spring, and then venting or removing the lid allows the surface to dry so the Maillard reaction (browning between amino acids and sugars at 140–160°C) and sugar caramelization above 160°C can produce color and flavor. Without sufficient steam, the crust becomes thick, leathery, and splits randomly. High heat combined with surface moisture can also create a rustic blistered crust, often in long-fermented, high-hydration doughs. Oven spring is the rapid expansion in the first ten minutes of bake from heat-released CO₂ and steam — the aim is a visible leap in volume. Internal temperature of 96–99°C, confirmed with a probe thermometer, signals doneness.

Standard loaf shapes include the boule (round, free-form, rising straight up from a round base — best oven spring and most forgiving of shaping errors, since round tension is more forgiving than oval), the batard (oval, slightly elongated, scored diagonally, requires tighter shaping or it flattens during proof), the bloomer (oval like a rolling pin, ideal for slicing for sandwiches and toast), and the pan loaf (baked in a loaf pan for easier shaping and even crumb at the cost of a thinner crust and a less dramatic ear). A tin loaf is an open-top Pullman-style pan that yields a square-sided loaf, while a pan loaf has one open side and produces tall sandwich slices with a side crust. To bake in a loaf pan, grease the pan, place shaped dough, proof until just above the rim, cover with foil for 20 minutes, then uncover and bake for 20–25 minutes at 200–220°C.

Crumb is the interior structure of the loaf — the network of holes and walls — while the crust is the outer baked shell. An "open" crumb has large irregular holes from strong gluten and sufficient fermentation; a "tight" crumb is dense, often from under-fermentation or over-degassing (degassing means releasing gas from the dough, though in sourdough this is usually gentle rather than the full degassing done in baguette dough). The Italian and French term for those gas pockets is alveoli, so "open alveolation" simply means holey crumb. The ideal crumb has even, glossy holes with thin cell walls, is moist but not gummy, with a slight chew and a balanced sweet-sour-malty flavor. Tunnel-like holes come from over-shaping or aggressive degassing before final proof — the gentler the final shape, the more large pockets survive. To get more open crumb generally, bakers reach for higher hydration, stronger flour, fewer but larger folds, longer bulk fermentation, and careful final shaping that preserves large gas pockets.

The poke test confirms proofing status: a slow rebound means ready to bake, a quick snap-back means under-proofed, and a dent that stays with no rebound means over-proofed. Under-proofed crumb is tight, gummy, and dense with a pale ear; over-proofed crumb has large uneven holes, a flat loaf, sour and raw-tasting interior, and tends to collapse on cooling. Dense or gummy crumb usually means under-proofing or under-fermentation, or slicing too warm — bread should rest at least an hour before cutting, ideally two to four, as starches continue to gel and crumb bloom (the slight opening of structure as the loaf cools) develops. Cutting too early causes a gummy interior; even overnight develops flavor.

Storage depends on how soon the bread will be eaten. Cut sourdough stays fresh for one to two days when stored cut-side down on a board or in a paper bag that keeps the crust crisp; plastic softens the crust quickly. Longer storage means freezing: slice the whole loaf, wrap tightly in plastic and foil, and freeze up to three months, then toast slices straight from the freezer. To refresh slightly stale bread, mist it lightly with water and bake at 200°C for 5–8 minutes to restore crust crunch, or cube it for croutons and panzanella.

Other common problems have specific fixes. Pale crust means the oven is too cool or the bake too short — Maillard reactions need 230°C-plus for color even when the internal temperature is done. Overly sour bread comes from long fermentation with abundant acetic acid; reduce bulk time, feed starter more often, or lower starter hydration to tame it. Flat dough that won't rise points to a weak starter, over-fermented collapsed gluten, or bulk temperatures that are too cold. When dough is over-fermented and unrecoverable for shape, pour it into an oiled pan, dimple with fingers, top with olive oil and salt, and bake at 230°C for an excellent focaccia. Dough sticking to the banneton traces to insufficient flour, dough that is too wet, or a proof that has run too long. Crust that is too thick indicates over-baking or excess steam that kept gelatinizing the surface, so total bake time should be shortened and steam vented earlier. A rubbery crust means under-baking or insufficient rest; bake until deep brown and cool fully so moisture redistributes and the crust crisps.

A cold bulk ferment — keeping the dough at fridge temperature for 12–24 hours during its first rise — slows yeast so the dough stays under-proofed for longer while developing strong, complex flavor. It pairs naturally with double hydration (reserving a portion of the water to add after the initial mix, particularly useful with whole grains that absorb aggressively) or bassinage (the French term for adding extra water gradually during mix to reach a target hydration, especially helpful for high-hydration doughs). Whole-grain levains feed microbes faster and lead to more vigorous oven spring than white-flour levains, and using a mother dough kept continuously as a large levain is common in bakeries though less typical at home. A 100 percent rye starter, sometimes called a rye sour, ferments aggressively and brings sharper tang, a staple in German and Eastern European breads. Bakers can also use a stiff starter directly without an intermediate levain build, particularly for low-inoculation recipes, though adjustments are needed since stiff starter ferments more slowly.

Pre-ferments in general are portions of dough fermented before final mix, and they boost flavor and extensibility. Stiff levains fermented cool and long produce more acetic acid for sharper tang; liquid levains produce more lactic acid for milder, yogurty flavor. Starters vary in sourness based on hydration, temperature, flour type, age, and feeding ratio — stiff, cool, whole-grain starters are tangiest, while young liquid white-flour starters are milder. The poolish is a liquid French preferment at 100 percent hydration built with commercial yeast. The biga is a stiffer Italian preferment at about 50 percent hydration, also commercial-yeast based. A levain is the same preferment concept but built with wild sourdough culture, while a detrempe is the initial flour-and-water mix in laminated doughs before fat and salt are added.

Inclusions — seeds, nuts, oats, cheese — should be soaked in water before being added to the dough so they don't draw moisture from the crumb, and the best moment is at lamination or the first stretch-and-fold so they distribute evenly without being broken up. Shaped dough can also be frozen: proof, freeze unwrapped for one hour, then wrap tightly and store up to one month; thaw in the fridge overnight before baking. This "thaw and prove" approach, common in artisan bakeries with cold retarders, lets bakers stage doughs in advance. Higher inoculation rates of 20–25 percent levain produce faster bulk, more open crumb, and less sour flavor, while lower rates of 10–15 percent produce longer bulk with deeper, more tangy flavor. To build fermentation tolerance and tame schedule pressure, bakers can lower inoculation to 10–12 percent, cool the dough to 22–24°C, build a stiff levain, or pre-shape and refrigerate the bulk. The combined toolkit of cold bulk, stiff levain, low inoculation, whole-grain flour, and soakers lets a baker dial flavor, sourness, and crumb character with remarkable precision.