Design Sourdough Process

---
name: design-sourdough-process
description: Use when making sourdough bread from scratch — maintaining a starter, mixing dough, managing fermentation, shaping, and baking — to produce an open-crumb, well-flavoured loaf with a crackly crust
source: 'Robertson "Tartine Bread" (2010); King Arthur Baking sourdough guide (2023); Modernist Bread vol.2 (Myhrvold & Migoya, 2017); Hamelman "Bread: A Baker''s Book of Techniques and Recipes" (2nd ed., 2004)'
tags: [baking, sourdough, bread, fermentation, starter, levain, dutch-oven, gluten]
verified: true
---

# Design Sourdough Process

Maintain a live starter, develop gluten through folding, cold-retard for flavour, and bake in a sealed vessel to produce a well-risen loaf with crackly crust and open crumb.

## Why This Is Best Practice

**Adopted by:** Tartine Bakery (Chad Robertson) popularised the modern sourdough method — now used by artisan bakeries worldwide and home bakers following Robertson's open-crumb, high-hydration approach. King Arthur Baking's sourdough guide is the reference used by the largest sourdough community in the US. The Bread Lab (WSU) and The Modernist Bread team validated the science behind long cold fermentation and Dutch oven baking through controlled experiments.

**Impact:** A well-executed sourdough loaf requires no commercial yeast, no preservatives, and produces a more digestible bread than commercial sandwich bread (longer fermentation partially breaks down phytic acid and some gluten proteins). Home baking cost is ~$0.50–1.00/loaf vs. $8–12 for equivalent artisan bread. Mastering the process gives full control over flavour (more/less sour), crumb structure (open vs. tight), and crust (thin/thick).

**Why best:** The Robertson method — autolyse, stretch-and-fold in lieu of kneading, long cold retard — produces more flavour and better crumb structure than short-mix, room-temperature methods. The Dutch oven replicates commercial deck ovens: trapped steam keeps crust extensible during oven spring; removing the lid browns and crisps it. These steps are not arbitrary; each has a documented biochemical function.

Sources: Robertson, *Tartine Bread* (2010) — bulk fermentation and fold timing; Hamelman, *Bread* (2nd ed., 2004) — gluten development science; Myhrvold & Migoya, *Modernist Bread* vol. 2 (2017) — heat transfer and crust formation; King Arthur Baking (2023) — starter maintenance ratios

## Steps

### Step 1: Maintain a healthy starter
A starter is a live culture of wild yeast and lactic acid bacteria. Without a healthy starter, nothing else works.

**Feeding ratio:** 1:5:5 (1 part starter : 5 parts flour : 5 parts water by weight). Use unbleached all-purpose or bread flour; whole wheat or rye accelerates fermentation (more nutrients for bacteria).

**Feeding schedule:**
- **Active baking:** Feed every 12 hours at room temperature (70–75°F / 21–24°C). Use the starter when it has doubled and is just beginning to dome or fall — this is peak activity.
- **Maintenance:** Keep in the fridge. Feed once a week. Remove from fridge 4–12 hours before baking and feed once to reactivate.

**Float test:** Drop a teaspoon of starter into water. If it floats, it has enough gas to leaven bread. If it sinks, feed again and wait.

**Signs of a healthy starter:** Doubles in 4–8 hours after feeding; smells pleasantly sour and yeasty (not vinegary or acetone-like); shows a domed surface with visible bubbles.

### Step 2: Mix the dough — autolyse first
Autolyse is a 30–60 minute rest after mixing flour and water before adding starter and salt. It allows gluten to hydrate and partially develop without kneading, producing more extensible dough.

**Basic ratio (one loaf, ~900g baked weight):**
| Ingredient | Weight | Baker's % |
|------------|--------|-----------|
| Bread flour | 400g | 80% |
| Whole wheat flour | 100g | 20% |
| Water (lukewarm, ~80°F) | 375g | 75% |
| Active starter | 100g | 20% |
| Salt | 10g | 2% |

1. Mix flour and 350g of the water (hold back 25g) with your hand until no dry flour remains. Cover and rest 30–60 minutes.
2. Add starter and remaining water. Squeeze through your fingers until fully incorporated.
3. Add salt. Squeeze again until incorporated. The dough will feel slack and rough.

### Step 3: Bulk fermentation with stretch-and-fold
Bulk fermentation develops gluten, builds flavour, and raises the dough. For a 75% hydration dough at 75°F, bulk fermentation takes approximately 4–5 hours.

**Stretch and fold:** Every 30 minutes for the first 2 hours (4 total sets).
- Wet your hand. Grab one side of the dough, stretch it up as far as it will go without tearing, fold it over to the opposite side. Rotate the bowl 90° and repeat. Complete all four sides = one set.
- Each set strengthens the gluten network. After 4 sets, the dough should feel noticeably stronger and more elastic.

**Signs bulk is complete:**
- Dough has grown 50–75% in volume (not necessarily doubled)
- Surface is domed, with visible bubbles underneath
- Dough jiggles like jello when you shake the bowl
- A small piece stretched between your fingers shows a thin, translucent windowpane (gluten window test)

**Temperature matters:** Colder dough ferments slower. If your kitchen is 65°F, add 1–2 hours. If 80°F, subtract 1 hour. A proofing box or oven with just the light on (~78°F) is ideal.

### Step 4: Pre-shape
Turn the dough onto an unfloured surface. Using a bench scraper and your other hand, drag the dough toward you in a circular motion, building tension on the surface. The dough should tighten into a ball. Rest 20–30 minutes uncovered (bench rest).

### Step 5: Final shape
Flour the surface lightly. Flip the dough. Stretch it gently into a rough rectangle. Fold the sides in, then roll it toward you into a tight cylinder (batard) or pinch the edges into a ball (boule). Place seam-side up in a well-floured banneton (proofing basket) or a bowl lined with a heavily floured cloth. Dust the top of the dough with flour.

### Step 6: Cold retard
Cover tightly with plastic wrap or a shower cap. Refrigerate 12–16 hours (up to 24 hours).

Cold fermentation develops flavour: the long, cold environment favours lactic acid bacteria that produce acetic acid (the sharp, tangy notes) in addition to lactic acid (the mild, yogurt-like notes). Longer cold retard = more sour flavour. Baking cold dough directly from the fridge also produces better oven spring and makes scoring easier.

### Step 7: Preheat the Dutch oven
Place a lidded Dutch oven (5–7 qt, cast iron) in the oven. Preheat to **500°F (260°C)** for at least 45 minutes. The Dutch oven must be screaming hot.

### Step 8: Score and bake
1. Remove dough from refrigerator. Place a sheet of parchment paper over the banneton and flip it. The dough should release seam-side down.
2. Score quickly with a sharp blade (lame, razor blade, or sharp serrated knife) at a 30–45° angle. A single slash 4–6 inches long down the centre is sufficient. Scoring controls where the loaf expands and prevents blowouts.
3. Carefully lower the parchment and dough into the preheated Dutch oven. Cover with lid.

**Bake schedule:**
- **20 minutes at 500°F (260°C) with lid on** — Steam trapped inside allows the crust to remain extensible during oven spring. The loaf rises significantly in this phase.
- **20–25 minutes at 450°F (230°C) with lid off** — Crust browns and crisps via Maillard reaction and caramelisation.

The loaf is done when the internal temperature reaches **205–210°F (96–99°C)** and the crust is a deep mahogany brown. Tap the bottom — it should sound hollow.

### Step 9: Cool completely before cutting
Transfer the loaf to a wire rack. Cool for a minimum of 1 hour, ideally 2. Cutting hot bread compresses the crumb and releases steam that would otherwise set the interior structure. The crumb continues cooking from residual heat after you remove it from the oven.

## Rules

- Never add salt at the same time as the starter — salt inhibits yeast activity. Add sequentially, not simultaneously.
- Maintain baker's percentages: changing hydration changes everything. Start at 75% and adjust once you understand the dough's feel.
- If the dough isn't rising after 2 hours at bulk start, your starter was not active enough. There is no rescue — start over with an active starter.
- Score decisively with one motion. Hesitating tears instead of cuts.
- Do not open the Dutch oven during the first 20 minutes of baking — releasing steam prevents oven spring.
- Whole grain flour absorbs more water. Adding whole wheat or rye will make the dough stiffer; compensate by adding 10–20g more water per 100g whole grain added.

## Examples

**Standard Tartine-method country loaf:**
- 80% bread flour, 20% whole wheat, 75% hydration, 20% starter, 2% salt
- Autolyse 45 min → add starter + salt → 4 stretch-and-folds at 30-min intervals → bulk 4.5 hours at 76°F → pre-shape → bench rest 25 min → final shape → banneton → refrigerate 14 hours → bake 500°F/20 min lid on, 450°F/22 min lid off
- Result: open crumb, crackly crust, mild-to-moderate tang

**High-hydration loaf (for very open crumb):** Increase water to 80–82% hydration. Use wet hands for all folds. Expect stickier dough throughout; do not add flour. Requires confident shaping — the dough is extensible but fragile.

**Faster same-day loaf:** Increase starter to 30%, ferment at 80°F. Bulk will finish in 3–3.5 hours. Flavour will be milder (less acetic acid). Skip cold retard; shape, proof at room temperature 1–2 hours until dough passes poke test (indent springs back slowly), then bake.

## Common Mistakes

**Under-fermented bulk (most common):** Dough that hasn't risen enough is dense, gummy, and tastes raw. Cause: starter not active, kitchen too cold, or bulk cut short. Signs: loaf doesn't spring in the oven; crumb is dense and gooey.

**Over-fermented bulk:** Dough is sticky, slack, won't hold shape. The gluten network has been degraded by enzymatic activity. Cause: too warm, too much starter, bulk too long. Prevention: watch the dough, not the clock.

**Not flouring the banneton enough:** Dough sticks and tears during the flip. Use 50/50 rice flour and all-purpose flour (rice flour doesn't absorb moisture and prevents sticking far better than all-purpose alone).

**Scoring too shallow or too straight:** A shallow score seals; a 90° angle score traps the blade. Score at 30–45° angle, at least ¼ inch deep, in a single confident motion.

**Cutting before cooling:** The interior is still steaming. Cutting hot bread produces a compressed, gummy crumb. Wait the full hour minimum.