First loaf, 70%

The schedule

Times are for dough at 75°F (24°C). Start to finish: 29h 58m at 68°F, 26h 2m at 75°F, 24h 3m at 80°F. Filled steps get longer or shorter with temperature. The rest stay the same.

1. 1
   0:00 · 5h

   Build the levain

   Mix the levain weights from the formula card. Ready when it has roughly doubled, domed and is just starting to flatten, and smells sweet-sour rather than sharp. Starter straight from the fridge works, but can take an hour or two longer.

2. 2
   5:00 · 15m

   Mix everything

   Flour, water, levain and salt together from the start. Squeeze and fold for two or three minutes until it is one shaggy mass.

3. 3
   5:15 · 45m

   Bulk ferment

   Cover and keep it somewhere warm and draught-free. First fold in 45 min.

4. 6:00 · 45m

   Fold 1 of 3

5. 6:45 · 45m

   Fold 2 of 3

6. 7:30 · 45m

   Fold 3 of 3

7. 4
   8:15 · 1h 30m

   Bulk, hands off

   No more folding. Bulk is done when the dough has risen roughly 50%, domed, and feels airy — jiggly, not soupy. Read the dough, not this clock.

8. 5
   9:45 · 5m

   Pre-shape

   Tip the dough out onto a bare counter and fold it into a loose round with a bench scraper.

9. 6
   9:50 · 20m

   Bench rest

   Uncovered.

10. 7
    10:10 · 10m

    Shape and basket

    Fold to a tight parcel, seam up in a floured bowl lined with a tea towel.

11. 8
    10:20 · 12h

    Cold proof

    Fridge overnight. Cold dough is far easier to score.

12. 9
    22:20 · 1h

    Oven on

    475°F / 245°C, Dutch oven preheated inside. Give the pot at least 45 minutes at temperature. Glass lid or plastic knob? Check its heat rating first. If it is lower than this, fit a metal knob, or bake on a stone with a pan of steam instead. The loaf can wait in the fridge until the pot is hot. Enamelled or ceramic pot? Check its maker's care notes on heating it empty, and take the loaf out when the oven reaches temperature: a fridge-cold loaf can crack a hot pot.

    Sources King Arthur Baking: Artisan sourdough bread tips, part 3·Lodge Cast Iron: Cleaning and care: enameled cast iron

13. 10
    23:20 · 22m

    Bake covered

    Turn the dough out onto parchment, score it in one confident stroke about 1 cm deep, lower it in, lid on.

14. 11
    23:42 · 20m

    Lid off

    Drop the oven to 450°F / 230°C. Bake until the crust is deep brown — darker than feels comfortable. A thermometer in the centre should read at least 190°F / 88°C.

    Sources King Arthur Baking: Using a thermometer with yeast bread

15. 12
    24:02 · 2h

    Cool before cutting

    On a rack, at least two hours. The crumb is still setting; cutting early is what makes a loaf gummy.

    Sources King Arthur Baking: How to tell if bread is done baking