I’ve learned that when three key elements are in place—your starter is thriving (with a strong yeast population and a balanced acid load), you’ve chosen the right flour (strong, with good gluten-binding qualities), and your process is dialed in (developing the gluten network fully and supporting fermentation properly)—bulk fermentation becomes flexible.
Yes! When these foundational parts are working, the length of bulk fermentation can be adjusted to suit your goals for the final loaf. It’s not rigid. You gain the freedom to shape the process based on what kind of bread you’re aiming for. But, how exactly does a shorter or longer bulk fermentation make a difference?
In This Post
Background Knowledge
So, what’s really happening during bulk fermentation that makes it so powerful—and so flexible?
This is the phase where your dough changes on a structural and chemical level. Enzymes, yeast, and bacteria are all actively at work, reshaping the dough from the inside out.
- Proteases (an enzyme) break down proteins in the flour, making the dough stretchier and easier to work with. They also help improve digestibility.
- Yeast feed on sugars (broken down from starches by enzymes like amylases) and produce carbon dioxide. That gas becomes trapped in the gluten network and causes the dough to rise.
- Bacteria produce acids that lower the pH of the dough. This boosts flavor, speeds up enzyme activity, and improves shelf life.
So it’s not just about puffing up the dough. Bulk fermentation also builds flavor, softens texture, and for some people, mass the bread easier to digest.
But beyond these practical aspects (texture, flavor, and digestibility) bulk fermentation also has an impact on crumb, volume, and oven spring. While not essential to making good bread, many bakers chase openness, height, and expansion in the oven. For the dedicated baker, these are undeniably fun benchmarks. It’s where things get interesting: the air accumulated from fermentation now serves another purpose—it becomes a building block of structure.
Structure Through Air + The Crumb Connection
The air from a strong, vigorous, extended bulk fermentation becomes part of the dough’s internal framework, reinforcing its structure and helping shape the final loaf. It has a major impact on loaf volume, height, oven spring, and crumb. A well-structured loaf isn’t made solely from aggressive kneading or high tension; instead it relies on a perfect balance of gluten elasticity, gas accumulation, and tension (through folds and proper shaping).
This means that —all else being balances—a strong, vigorous, extended bulk fermentation can create a taller, more voluminous loaf with a greater oven spring and more open crumb. This is because the extra air adds size (it does take up space, after all), strength (think of the wonders air does to an air mattress; it’s so strong you can sleep on it!), and openness (because each alveolus is filled with air, held tightly inside by a firm gluten structure).
That’s what makes a longer bulk fermentation so interesting. It’s another way to build strength and volume, not by force, but through time and fermentation.
But bulk fermentation also shapes the bread’s crumb structure. If it’s cut short, you’ll see wild, uneven air pockets scattered between underdeveloped alveoli—those tiny balloons that haven’t had time to fully inflate. Let it go a little longer, and the chaotic pockets disappear. The structure stays strong, but the alveoli still aren’t fully expanded, so the crumb remains tight. With just the right amount of fermentation, the gluten network holds firm, the alveoli are full, and the crumb opens up beautifully. Push it too far, though, and the structure starts to soften. As lactic acid builds, it weakens the gluten, allowing air to distribute more evenly, resulting in a more uniform crumb again.
So the challenge is finding the sweet spot—just the right balance to achieve everything: your preferred texture, flavor, loaf volume, height, oven spring, and crumb.
A Surprisingly Wide Window
People have long debated the sweet spot for bulk, but I’m here to tell you that it really is flexible. You can achieve great results in all the categories I mentioned previously with a bulk fermentation ranging from six to ten hours (ambient temperature around 73–75 For 23–24 C). Really. As long as your starter is strong, your flour is dependable, and your process is balanced, the dough can remain stable and responsive across a much wider window than many believe.
This experiment is meant to show you the differences in a shorter versus a longer bulk fermentation, but all in the range for a quality fermentation. Here, I tested the difference between a 6.5, 7.5, and 8.5 hour bulk.
The Hypothesis
A recent video left me baffled: the baker had achieved a wildly open crumb with a much shorter fermentation and a more elastic dough than mine. Being an avid proponent of extended fermentation, it made me wonder if I have been fermenting my dough for too long this whole time.
I began to suspect that a shorter bulk might be the key to a wilder crumb, albeit a denser bread. of course, it would still need to have enough fermentation to eliminate obnoxious air pockets and create evenness. And, of course, factors like acid development and dough elasticity play a role, too. But, what if I could isolate the effect of bulk fermentation alone?
I needed to see for myself how shortening or lengthening this factor would impact the bread, using my own process. I already knew my starter was in top shape, my flour was dependable, and my method produced consistent results. This made it the perfect scenario for testing one variable: fermentation time.
I typically prefer a bulk fermentation between 7.5–8 hours at an ambient temperature of 73–75 F (23–24 C), and sometimes I push it even longer. But lately, I’ve been wondering: Have I been going too far? Could a shorter bulk fermentation yield a more striking crumb? I needed to find out.
The Experiment
For this experiment, I didn’t want to waste too much flour on large loaves, so I divided my recipe into thirds to make three mini loaves. I used the same process for each one, fermented them side-by-side in the same environment, and even baked them together in the Dutch oven.
One possible concern with the smaller loaf size was that the dough might heat up more quickly during bulk fermentation. Smaller dough masses adjust to ambient temperature (hot or cold) faster than larger ones. This could mean that 6.5 hours of fermentation in a mini-loaf might reflect the effects of 7 or even 7.5 hours in a larger one. In other words, less fermentation time, but more fermentation actually happening.
In the end, though, this didn’t pose a problem. The results were surprising, and the experiment turned out to be a striking visual confirmation of things I already understood about bread dough.
Since I usually bulk ferment my dough around 7.5 hours, I wanted to see the effect of a slightly shorter bulk and a slightly longer bulk. Therefore, I fermented one of the mini-loaves for 6.5 hours, (one hour shorter), one for 7.5 hours (the usual, my control and comparison), and one for 8.5 hours (one hour longer, to see what would happen).
The Dough + Process
Each dough was made with 115 g breadflour, 2 g salt, 95 g filtered water, and 23 g ofactivestarter at 85% hydration.
They fermented at an ambient temperature of 72–74 F (22–23 C), just a tad cooler than my usual range of 73–75 F (23–24 C).
Since I used the premix method, I first mixed the flour, salt, and water together, then let the mixtures rest for two hours before adding the starter.
After the two-hour rest, I added the starter to each dough. By this point, the gluten network was fully developed, so I folded in the starter using a combination of coil folds and rolling the dough up multiple times to create as many layers as possible.
Thirty minutes later, I laminated each dough. This helped further incorporate the starter, but also added tension to the gluten strands and strength to the dough.
One hour after lamination, I gave each dough a single set of coil folds—just enough for it to stand tall and feel supported.
Two hours after the first set of coil folds, I gave each dough another, final set of coil folds.
After that, I let the doughs rest undisturbed for the remainder of their bulk time. I shaped and retarded one loaf at 6.5 hours, one at 7.5 hours, and one at 8.5 hours, using a gentle shaping method (see visual here).
The difference at shaping was striking. The 6.5-hour dough was clearly smaller, still slightly sticky, but very strong. There were no large air bubbles to pop. The 8.5-hour dough, on the other hand, was big and filled with large bubbles (some of which I had to deflate). Unsurprisingly, the 7.5-hour loaf fell somewhere in between: slightly larger than the 6.5, with a few big bubbles but not nearly as gassy as the 8.5. You can check out my Instagram reel here (if you’re reading this now, you’re one of the first and it’s not yet posted!) to see for yourself.
The next day, I baked all three loaves together in a preheated cast iron vessel at 450 F (230 C): 20 minutes with the lid on, 15 minutes with the lid off. The results shocked me.
The Results
From the outside, the 6.5-hour and 7.5-hour loaves looked pretty similar. Both had a decent expansion (the 6.5 slightly more) and a quirky blowout-like burst on the right side. Interestingly, that blowout didn’t affect the crumb—it was just the way the loaves expanded in the oven. The 6.5-hour loaf stood a bit taller than the 7.5-hour and had more blisters than the others, likely due to higher moisture from les fermentation.
The 8.5-hour loaf, though? It absolutely had the best shape: round, full, with stunning oven spring. I was honestly surprised, especially considering how gassy it felt during shaping. I mean, we already know gas has these effects (see this section above if you missed my spill), but I thought maybe lactic acid would have messed things up. It didn’t.
The real difference, though, was inside.
The interior is where it’s at! The 6.5-hour loaf (top) did have big bubbles, but not in a desirable way. While this loaf was still fermented in an acceptable fermentation range, the loaf just seemed under-fermented to me. The crumb wasn’t even; it had three large air pockets that just got in the way.
The crumb of the 7.5-hour loaf was much more even, and its height difference is clear in the photo above. You would almost expect that this loaf was over-fermented, but it was not. It really appears that this loaf just needed more air to help with crumb and structure.
Last, the 8.5-hour loaf was here to impress! (Obviously, my favorite.) I mean, look at that crumb. Even, open. And it’s clear just how perfect this loaf expanded in the oven. It’s the tallest, with the most structure. Big and full.
Not pictured: texture. Of course, the 6.5-hour loaf was the most dense, while the 8.5-hour loaf was the lightest. Overall, though, I would eat any of these loaves; none was too chewy for my preference.
The Conclusion
Maybe the difference between my loaf and the one from the video came down to the flour and not fermentation. I mean, yes, fermentation was different, but various flours can require differences in both fermentation time and how elasticity is developed. A weaker flour won’t hold air as easily, so it needs more strength and structure, yet still can’t always support a long fermentation without breaking down.
As for my flour, my process… I think I just proved to myself that the longer fermentation is the way to go. 8.5 hours for the win!
