The Ultimate Guide to Sourdough Bulk Fermentation

Bulk fermentation is one of the most misunderstood steps in sourdough bread baking, but it is also one of the most important.

In this guide, you will learn what bulk fermentation is and when it begins and ends. You will also discover how long it takes, how temperature affects the process, and how much your dough should rise.

What is bulk fermentation in sourdough?

Bulk fermentation is the first rise in sourdough bread-making, which happens after mixing and before preshaping.

During this phase, gluten strengthens and traps carbon dioxide gas, causing the dough to rise. Stretch and folds and coil folds help align the gluten strands, improving the dough's elasticity and ability to hold gas.

At the same time, lactic acid bacteria ferment the sugars in the flour, creating a sourdough signature tang.

Dough temperature plays a key role in bulk fermentation. Warmer dough (75-80°F / 24-27°C) ferments faster (warm bulk), while cooler dough (below 75°F / 24°C) ferments more slowly (cool bulk).

Note: Cool bulk fermentation is not the same as cold proofing, which happens in the fridge at 39°F (4°C).

When does bulk fermentation start and end?

Bulk fermentation starts when you mix the preferment (levain or active starter) into the dough and continues until the dough is pre-shaped.

If you add salt as the last ingredient, bulk fermentation starts once all the ingredients are mixed together.

Although bulk fermentation ends when the dough is pre-shaped, the fermentation process continues through bench rest, shaping, final proofing, scoring, and even a few minutes of baking.

How long does bulk fermentation take?

Bulk fermentation usually takes between 3 and 9 hours (sometimes longer), depending on several factors. There is no fixed time because fermentation time varies from one kitchen to another and from one dough to the next.

Here is what affects how long bulk fermentation takes:

• Dough temperature: Warmer dough (around 75-80°F / 24-27°C) ferments faster. Cooler dough (60-70°F / 15-21°C) takes longer.
• Starter strength: A well-fed, active starter will speed up fermentation. A sluggish one will slow it down.
• Flour type: Whole-grain flours ferment faster than white flours due to their higher enzyme and nutrient content.
• Dough hydration: Higher-hydration doughs tend to ferment more quickly (see my guide on high vs. low sourdough hydration).

Due to these variables, the length of bulk fermentation cannot be directly copied from a recipe. Even if a recipe says "bulk ferment for 4 hours," that is based on the author's conditions.

Your own kitchen may be warmer or cooler, which affects the actual fermentation time. For example, at room temperatures of 68°F (20°C) and 75°F (24°C), the bulk fermentation speed and duration will be different.

Instead of relying on a set number of hours, pay attention to dough temperature and how much the dough has risen. This, with visual signs, will give you the most accurate picture of when bulk fermentation is truly complete.

What is the best temperature for bulk fermentation?

There is no single best temperature for bulk fermentation. It depends on your kitchen temperature. A warmer environment speeds up fermentation, while a cooler environment slows it down.

The dough temperature can range anywhere from 60°F (15°C) to 90°F (32°C), but it ferments best between 75°F and 80°F (24°C to 27°C).

If you are a beginner, try to keep your dough temperature below 80°F (27°C). Otherwise, pay close attention to the dough and use a tool like the Bulk-o-Matic Guide to track your bulk fermentation.

How dough temperature affects bulk fermentation

Bulk fermentation is all about dough temperature and percentage rise. The time it takes for the dough to ferment depends on how fast it rises, which in turn depends on the dough temperature.

Warmer dough (above 75°F / 24°C) will ferment more quickly, requiring less time to reach the desired rise. Cooler dough (below 70°F / 21°C) will slow things down. Room temperature alone is not a good guide. You should always measure the dough temperature, not the air.

An excellent bulk fermentation method was developed by Tom Cucuzza, who created a chart linking dough temperature to the target rise percentage for the end of bulk fermentation. You can read his detailed bulk fermentation guide and print his bulk fermentation chart to keep in your kitchen.

In this method, the dough temperature determines the fermentation time, not the clock. It has helped many sourdough bakers. It works well for sourdough bread recipes that include a long, cold final proof in the refrigerator (8 to 16 hours).

It is important to note that Tom Cucuzza's guidelines were designed for a Tartine Country Bread recipe using:

• 90% bread flour (12.5% protein)
• 10% whole wheat flour
• 75% hydration
• 20% starter
• 2% salt

If you use a different flour blend, hydration level, starter amount, or a different final proof method, you will need to adjust the guidance accordingly.

Bulk fermentation is about adapting and refining this method and your technique.

Your kitchen is unique in terms of room temperature and humidity, and your starter is different from the one used in the sourdough bread recipe you are following. Learn how to adjust bulk fermentation to match your own kitchen in this post.

How much should sourdough rise during bulk fermentation?

Although many recipes suggest that the dough should double in size during bulk fermentation, focus on checking the dough temperature and percentage rise.

If you let the dough rise until it doubles in size, it often leads to overproofing, especially if you plan to cold-proof it overnight. The dough will continue to rise in the fridge, so if it doubles on the counter, it may overproof while chilling (see my guide on overproofed sourdough bread).

The dough temperature determines the rise during bulk fermentation. According to Mr. Cucuzza's guidelines, if the dough temperature is 70°F (21°C), aim for a 75% rise before shaping and refrigerating. At 75°F (24°C), target a 50% rise. If the dough reaches 80°F (27°C), aim for a 30% rise before transferring it to the fridge.

However, the target rise of your sourdough again depends on your kitchen temperature, your starter, and the recipe.

What is the best proofing container for bulk fermentation

The best proofing container is clear, straight-sided, smooth, and food-safe to prevent any reactions with the dough.

For smaller batches (around 500g of flour), choose a 2-quart Cambro container with clear markings and a lid. You can also use a 4-cup glass measuring cup or a 120-ounce large glass container with an airtight lid. If you make two loaves (500g of flour each), consider a 4-quart Cambro container.

Round containers are preferable over square ones, as they allow the dough to rise more evenly, without getting stuck in corners.

Those using the aliquot jar method (measuring dough rise with a small sample) use a 4-quart glass bowl for a single loaf of bread.

And for batch baking, you can use commercial bus tubs or stainless steel bowls to manage larger quantities of dough. If you own a Brod & Taylor folding proofer, a 2.75-gallon Rubbermaid tub is a perfect fit and can hold up to 8 kg of dough.

Another important tool is a digital probe thermometer. This tool helps you accurately check the dough temperature. Avoid infrared thermometers, which only measure the surface temperature, not the dough's core.

Top tips for perfecting bulk fermentation

• Use Tom Cucuzza's bulk fermentation chart as a guide, not a strict rule. Adjust fermentation to suit your kitchen conditions, starter, and recipe ingredients.

• Don't rely solely on recipe times. Bulk fermentation varies due to many factors. Instead, pay attention to your dough's rise and visual cues.

• Measure dough temperature after performing folds, not before. This provides a more accurate reading of its temperature. Then, continue checking the dough temperature every 30-40 minutes.

• Learn to read the dough. Over time, you will develop a sense of when your dough is ready, based on visual cues.

• Keep a sourdough baking log to track each baking session (download and print it out). By reviewing your notes, you will fine-tune your process and adapt to changing kitchen conditions.

FAQ

Should you cover the dough during bulk fermentation?
Yes, cover your dough with a lid, plastic wrap, or a damp kitchen towel to prevent it from drying out and forming a crust.

Should you oil the bulk fermentation container?
You can lightly coat the container with oil or spray it with nonstick cooking spray to prevent sticking. However, a properly fermented dough should usually slide out easily without oil.

Can you use a dough proofer for bulk fermentation?
Yes, a dough proofer, like a Brod & Taylor folding proofer, is a helpful tool for maintaining a consistent temperature, allowing the dough to ferment evenly and predictably.

Let's talk sourdough

How do you track bulk fermentation? Do you go by time, dough volume, texture, or a combination of factors? Share your method in the comments.

Ready to keep learning?

Bulk fermentation is key, but how do you know when it is done? Learn how to tell when to end bulk fermentation so your dough is ready for shaping.