And How to Know When It’s Done
Category: Sourdough Techniques | Read time: 8 min
I get versions of this question every week. A baker finishes their bulk ferment, shapes their loaf, tosses it in the fridge overnight, and then wonders: did the dough keep fermenting in the fridge? Is that the same thing as bulk? Should I do both? Do I have to do both?
The confusion is real, and it’s not your fault. Most beginner-friendly bread resources blur these two phases together or treat the cold retard like a bonus step you do if you’re serious. Neither framing is accurate.
Bulk fermentation and cold retard are two distinct phases that do fundamentally different things to your dough. Understanding what each one does, and what you’re watching for in each, will change how you bake.
What Is Bulk Fermentation?
Bulk fermentation is the first rise. It starts the moment you mix your starter into your dough and ends when you divide and pre-shape.
The word “bulk” just means the dough is fermenting as one large mass, before you’ve shaped it into individual loaves.
This is the most active fermentation window in your entire process. Your starter is eating the sugars in the flour, producing carbon dioxide and organic acids. The CO2 creates gas bubbles that give your dough lift. The acids build flavor. The gluten network, which you’ve been developing through mixing, folding, or both, is simultaneously getting stronger and more extensible.
Bulk fermentation is doing three things at once:
- Building volume and gas structure
- Developing flavor through acid production
- Maturing the gluten so the dough can hold its shape when baked
All three happen together, and they’re all temperature-dependent.
How Long Does Bulk Take?
This is where people get into trouble. You cannot go by time alone.
At 78°F (26°C) with an active starter, bulk might take 4 to 5 hours. At 68°F (20°C), you could be looking at 8 to 10 hours. Colder kitchen, slower fermentation. Warmer kitchen, faster. Stronger starter, faster. Weaker starter, slower.
Clock time is just a reference point. Your dough is the real indicator.
Need a visual walkthrough of the signs bulk is finished? Watch the classroom lesson here.
How to Know When Bulk Is Done
Here’s what you’re looking for:
Volume: The dough should increase between 50% and 75% from its starting size. A well-hydrated sourdough isn’t going to double in bulk the way a commercial yeast dough does. If you’re hitting 100% increase and your dough is still going, you’ve over-fermented.
Texture: The dough should feel airy and slightly domed when you press it gently. It should jiggle a little when you move the container. Early in bulk, dough is dense and flat. Fully fermented dough has life to it.
Bubbles: You should see bubbles on the surface and along the sides of the container. A clear container makes this easy to track.
The poke test: Press a floured finger about half an inch into the dough. If it springs back slowly and incompletely, you’re in range. If it springs back immediately, it needs more time. If it doesn’t spring back at all, it’s over-fermented.
The windowpane: Stretch a small piece of dough thin. If you can see light through it without it tearing, your gluten development is where it needs to be.
Use a straight-sided container and mark your starting volume with a rubber band. It removes the guesswork on the volume side.
What Is Cold Retard?
Cold retard is what happens after you shape your loaf and put it in the fridge.
It is not a second bulk ferment. It’s a slow, cold proof. The shaped dough continues to ferment, but at a dramatically reduced rate. The yeast activity slows significantly in the cold, but the bacterial activity that produces lactic and acetic acids keeps going at a lower level.
What this means in practice: the cold retard is primarily a flavor development and convenience tool.
Cold retard does three things:
- Slows yeast activity so fermentation doesn’t run away
- Continues acid production, building a more complex, sour flavor profile
- Firms the dough, making it easier to score and load into the oven
That third point is underrated. A cold dough straight from the fridge has more structural integrity than a room-temperature shaped loaf. It holds its ears, takes a cleaner score, and goes into the oven in better condition.
Is Cold Retard Required?
No. You can proof your shaped loaf at room temperature and bake it. Many traditional bread schedules do exactly that.
But cold retard gives you two things you can’t easily get otherwise: better flavor complexity and schedule flexibility. You shape at night, bake in the morning. The dough waits for you instead of the other way around.
How Long Can You Cold Retard?
Most shaped loaves do well in the fridge between 8 and 16 hours. Some bakers push to 24 hours or even 36 hours with a well-developed dough and a slightly under-fermented bulk.
The key is that your bulk fermentation needs to account for the extended cold time. If you fully fermented your dough in bulk and then cold retard for 24 hours, you risk over-fermentation by the time it hits the oven. You’d want to pull bulk a little earlier in that case.
How to Know When Cold Retard Is Done
This is less about “done” and more about “ready.”
Your shaped loaf should have increased in size modestly in the fridge, maybe 20 to 30%. It should feel cold and firm but not rock-hard. When you press it, it should spring back slowly.
The float test doesn’t apply here. The poke test does.
Most importantly: you bake cold retard loaves cold, straight from the fridge into the preheated dutch oven. Don’t let them warm up on the counter unless your loaf didn’t proof fully in the fridge.
The Relationship Between the Two Phases
Here’s the part that clears up Shirley’s question and questions like it.
Bulk fermentation and cold retard are sequential phases, not parallel options. You don’t choose one or the other. You do bulk first, then you can choose whether to proof at room temperature or do a cold retard.
The way they relate:
- A fully fermented bulk + short cold retard (8-12 hours): Great balance of flavor and spring. Classic schedule for most home bakers.
- A slightly under-fermented bulk + long cold retard (18-24 hours): More acid development, slightly more sour. Good for bakers who want a pronounced flavor profile.
- An over-fermented bulk + any cold retard: The dough has already peaked. Cold slows things down but can’t reverse the damage. Expect a flat, dense loaf with a gummy crumb.
The cold retard doesn’t fix a bad bulk ferment. It continues from wherever bulk left off.
Common Mistakes That Come From Confusing the Two
Mistake 1: Treating cold retard as bulk fermentation Some bakers mix their dough, shape it immediately, and put it in the fridge thinking the fridge will do the bulk work overnight. This skips the active fermentation phase entirely. The result is an under-developed loaf with poor oven spring and weak flavor.
Mistake 2: Over-proofing because they don’t account for cold time If your dough is nearly fully fermented coming out of bulk and you then cold retard for 20 hours, you’ll likely over-proof. Plan your bulk to be slightly conservative if you’re doing an extended retard.
Mistake 3: Letting cold retard loaves warm up before baking A cold retard loaf bakes better cold. The thermal contrast helps oven spring. Letting it sit on the counter for an hour before baking often results in a sluggish score and softer crust.
Mistake 4: Starting cold retard too early If you shape under-fermented dough and put it straight in the fridge, you may end up with a loaf that never fully proofs. Cold is slow, not stopped. Your dough needs to be in the right fermentation window before the cold can do its job effectively.
Quick Reference
| Bulk Fermentation | Cold Retard | |
|---|---|---|
| When | After mixing, before shaping | After shaping |
| Temperature | Room temperature (68–80°F) | Refrigerator (38–42°F) |
| Duration | 4–12 hours (varies widely) | 8–24+ hours |
| Purpose | Gas production, gluten development, flavor | Flavor development, convenience, easier scoring |
| What to watch | Volume (50–75% increase), texture, bubbles | Modest increase, firm but pliable feel |
| Bake immediately after? | No, shape first | Yes, bake cold |
The Bottom Line
Bulk fermentation is where your bread becomes bread. It’s the primary fermentation window, the one you have to get right, and the one that sets up everything that follows.
Cold retard is a tool. It buys you time, builds flavor, and makes your scored loaves more precise. But it works on top of a completed bulk ferment, not instead of one.
Get your bulk right first. Then use the cold retard intentionally, not as a rescue move.
If you’re still unclear on whether your bulk is where it needs to be before you shape, that’s the question worth sitting with. The cold fridge will wait. Your dough won’t.
Questions about your bulk fermentation or cold retard timing? Drop them in the comments or bring them to the community. We’ve all had the flat loaf that taught us something.
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