America's Test Kitchen Sourdough Bread Recipe: Science-Backed Crust and Open Crumb

America’s Test Kitchen sourdough bread delivers restaurant-quality crust and an open, airy crumb—without the guesswork. This recipe breaks down their science-backed method into clear, foolproof steps, from starter maintenance to baking with precise oven temperatures. No more trial-and-error: just consistent results every time.

The secret lies in hydration control (65% for optimal texture) and autolyse—a resting period that develops gluten without overworking the dough. We’ll guide you through bulk proofing, shaping, and scoring for that signature open crumb, plus oven steam techniques to create a crackly crust. Even beginners can master this.

By the end, you’ll have golden-brown loaves with a crisp exterior and tender interior, perfect for toast or sandwiches. The recipe includes troubleshooting tips for dense bread or weak starters, ensuring success on your first try. Let’s bake bread that rivals artisanal bakeries.

Ready in 24 hours (including overnight proofing), this method turns sourdough from intimidating to reproducible. Store leftovers at room temperature for up to 3 days or freeze for longer shelf life. Your kitchen will smell like a Parisian boulangerie.

Ingredients for america's test kitchen sourdough bread

Six essential ingredients plus science-backed techniques for sourdough that rivals artisanal bakeries.

The sourdough starter is non-negotiable—it should be 100% hydration and bubbly with a slight tang. King Arthur or Bob’s Red Mill flours deliver consistent gluten development, but any high-protein flour works. For the water, room temperature is critical (cold slows fermentation, hot kills yeast). Diamond Crystal kosher salt dissolves more easily than table salt, so use that if you can. If your starter’s weak, feed it 1:1:1 (starter:flour:water) 12 hours before baking.

No King Arthur flour? Bread flour or all-purpose plus 1 tbsp vital wheat gluten gets you close. Cornmeal substitutes? Semolina or rice flour work, but cornmeal’s texture is ideal. The lame or razor blade should be sharp—dull blades tear dough instead of cleanly scoring. For steam, ice cubes in a tray below the baking stone creates the perfect humid environment, or use a spray bottle if you’re baking in a Dutch oven. Preheat your oven to 475°F with the baking stone inside for at least 60 minutes.

Starter keeps in the fridge for 2 weeks—feed it weekly. Flour lasts 6 months in a cool, dark place. The baking stone stays hot for hours, so use it for multiple batches. Store cooled loaves in a bread bag or wrapped in a towel to maintain freshness for up to 3 days. Freeze slices for 3 months—toast directly from frozen.

Step-by-step instructions for america's test kitchen sourdough bread

Here's the method that delivers that signature open crumb and crackly crust every time.

In a large bowl, combine the 0.5 cup active sourdough starter with the 3.25 cups distilled water and 1.5 tsp kosher salt. Let this hydrate for 5 minutes while you measure the flours. Add the 5 cups all-purpose flour and 1 cup King Arthur bread flour to the bowl, then mix using a dough whisk or your hands until just combined.

This initial mix should feel shaggy and sticky—don't worry, that's exactly what we want. The bread flour's higher protein content will develop gluten during the autolyse phase. Let the dough rest for 20 minutes covered with a damp towel. This resting period allows the flour to fully hydrate and the gluten to begin forming, creating a more extensible dough that will give you that signature open crumb structure.

After the initial rest, perform a series of stretch and folds every 30 minutes for 2 hours. Wet your hands to prevent sticking, then grab one side of the dough, stretch it upward, and fold it over itself. Rotate the bowl and repeat this process on all four sides. This technique strengthens the gluten network without overworking the dough.

You'll notice the dough becomes smoother and more elastic with each fold. After the final fold, let the dough rest for another 30 minutes. This final rest allows the gluten to relax slightly before shaping. The dough should be tacky but not wet—if it feels too sticky, you may need to add 1 tablespoon of flour at a time until it reaches the right consistency.

Turn the dough onto a lightly floured surface and shape it into a round boule. To do this, pull the dough toward you in a circular motion, tucking the edges under as you go. The goal is to create surface tension that will help maintain the shape during proofing. Place the shaped dough seam-side up on a floured piece of parchment paper.

Cover the dough loosely with plastic wrap and let it proof at room temperature for 1 to 1.5 hours, or until it has risen by about 50%. You'll know it's ready when the dough springs back slowly when poked gently with a finger. This proofing stage is crucial for developing flavor and achieving that open crumb structure. If your kitchen is cold, you may need to extend this time slightly.

Preheat your oven to 475°F with the baking stone inside. Place the 1 cup ice cubes in a heatproof container and position it on the lower oven rack. This will create steam during the initial baking phase, which is essential for developing that crackly crust. While the oven heats, dust a baking sheet with the 0.25 cup cornmeal—this will prevent the parchment paper from sticking.

Once the oven reaches temperature, carefully transfer the dough (still on its parchment paper) to the prepared baking sheet. Use the lame or razor blade to score the dough in a crosshatch pattern, about 1/8-inch deep. This scoring allows the dough to expand properly and creates those beautiful, irregular slashes on the crust. Immediately place the baking sheet on the middle rack and pour the 0.5 cup steam source (hot water) into the container on the lower rack.

Bake the bread for 20 minutes with the oven door slightly ajar to allow steam to escape. After 20 minutes, close the oven door and continue baking for another 20 to 25 minutes, or until the internal temperature reaches 205°F and the crust is deep golden brown. The bread is done when it sounds hollow when tapped on the bottom.

Remove the bread from the oven and let it cool on a wire rack for at least 1 hour before slicing. This cooling period is essential—it allows the crumb to set and prevents a gummy texture. The bread should have a crackly, crisp crust and an open, airy crumb with large, irregular holes. Serve warm or at room temperature for the best texture and flavor.

Storing and reheating your leftovers

Room Temperature Storage

Keep your freshly baked sourdough on a wire rack at room temperature for up to 3 days to maintain that perfect crust. I wrap mine in a clean kitchen towel or place it in a paper bag—this prevents moisture loss while allowing airflow.

The towel method mimics how bakeries store bread, keeping it crisp outside and soft inside. 🥖

Fridge Preservation

For longer storage, slice the loaf and freeze individual pieces in a ziplock bag—this way, you can toast directly from frozen. If storing whole loaves, wrap tightly in plastic wrap followed by aluminum foil.

Sourdough keeps in the fridge for 5-7 days, though I find the texture starts drying out after 3 days. Always let it return to room temperature before toasting for best results.

Freezing for Months

Freeze your sourdough for up to 3 months—this is my go-to method for meal prep. I slice the loaf first, then freeze the slices on a baking sheet before transferring to a ziplock freezer bag—this prevents them from sticking together.