Chapter 2: Building Your Dough
What is Bulk Fermentation?
Bulk fermentation—often simply called “bulk”—is the first long resting period after your dough has been mixed and strengthened. It is during this gentle phase that the wild yeast and bacteria in your starter begin their slow, symphonic work: developing flavor, aerating the dough, and transforming structure.
This is the soul of sourdough baking. Not rushed, not forced—just nature unfolding, guided by your careful eye.
Why It Matters
Bulk fermentation is where much of your loaf’s final volume, texture, and flavor are decided. When done well, it produces dough that is airy yet strong, with an elegant open crumb and the signature sourdough tang.
What’s Happening During Bulk Fermentation?
Wild yeast creates carbon dioxide, forming bubbles that lift and lighten the dough
Lactic acid bacteria add complexity, contributing to that beautiful sour flavor
Gluten continues to strengthen, aligning into long, elastic strands
Flour enzymes help convert starches into sugars, which enhance flavor and crust browning
How Long Does Bulk Fermentation Take?
Time is not fixed—it’s responsive. At room temperature (21–25°C / 70–77°F), bulk fermentation generally lasts 4 to 6 hours. Warmer rooms may shorten this, while cooler conditions will lengthen it.
Your goal is not just to watch the clock, but to observe the dough. Listen to its cues.
Visual Signs Your Dough is Fermenting Well
It becomes smoother and puffier
The surface gains a soft sheen
Gentle air bubbles appear beneath the surface
The dough jiggles slightly when the bowl is shaken
It roughly doubles in size, though don’t obsess over volume
Trust your eyes and hands more than your timer. Sourdough is alive—and life doesn’t always follow the clock.
Developing Strength During Bulk Fermentation
In sourdough baking, gluten strength is not built all at once—it’s coaxed gradually through a series of stretch & folds or coil folds, spaced 30–45 minutes apart.
These techniques help:
Strengthen gluten structure
Evenly distribute gases
Keep the dough aligned and elastic
Preserve lightness and open crumb
How to Perform a Stretch & Fold:
With damp hands, gently pull one edge of the dough upward
Stretch until just before tearing, then fold it over itself
Rotate the bowl and repeat 3–4 times until all sides are folded
Cover and rest until the next fold
Repeat this process 2 to 4 times during bulk fermentation.
Windowpane Test: Checking Gluten Development
Toward the end of bulk, gently stretch a small piece of dough between your fingers. If it forms a thin, translucent “window” without tearing, your gluten is well developed.
The Balance of Time and Temperature
A warm environment accelerates fermentation, but can lead to overproofing—a state where the dough becomes too gassy and weak to hold shape. Conversely, cool fermentation develops flavor more slowly and evenly.
Leviétte recommends aiming for a dough temperature of 24–26°C (75–79°F) for optimal flavor and structure. A simple kitchen thermometer can help you stay on course.
Signs of Under- or Over-Fermentation
Under-fermented
Sign: Dough is dense, tight, not risen
Solution: Extend bulk time; place in warmer spot
Perfectly fermented
Sign: Smooth, puffed, holds shape
Solution: Ready for shaping
Over-fermented
Sign: Dough is soupy, lacks strength, sour smell
Solution: Shorten bulk time for the next batch, or use less starter
The Art of Attention
Fermentation is not a passive process—it’s an act of presence. By observing texture, tension, and aroma, you begin to understand the rhythm of the dough and build trust in your instincts.
Fermentation teaches us that sometimes, the most beautiful things happen when we simply wait—attentively, gently, and with care.