The Complete Bulk Fermentation Guide

Bulk fermentation is the single most important stage in sourdough baking. Get it right and your dough will be easy to shape, spring well in the oven, and produce an open crumb. Get it wrong — in either direction — and no amount of skill at shaping or scoring will rescue the loaf.

This guide covers how long bulk fermentation takes, how to read the signs that it’s done, and how to troubleshoot the two most common failures: over- and under-fermentation.

What is Bulk Fermentation?

Bulk fermentation (also called the first rise or first proof) is the period between mixing your dough and dividing or shaping it. During this time, the dough ferments as one mass — hence “bulk.”

Two things happen simultaneously:

Yeast activity: Wild yeast consumes sugars in the flour and produces carbon dioxide. The CO₂ gets trapped in the gluten network, causing the dough to expand and become airy.

Bacterial activity: Lactic acid bacteria produce lactic and acetic acids. These acids develop the characteristic sourdough flavour, tighten the gluten structure, and contribute to the bread’s keeping quality.

The goal of bulk fermentation is to develop enough gas and flavour without over-fermenting — which breaks down the gluten and causes the dough to become slack and unworkable.

How Long Does Bulk Fermentation Take?

There is no single correct answer because bulk time depends on three variables: dough temperature, starter percentage, and flour type. Use the bulk fermentation calculator to get a time estimate for your specific conditions.

As a general reference:

These are estimates for white flour. Wholemeal flour ferments roughly 15% faster; rye can be 25–35% faster.

Why Temperature is the Biggest Variable

Yeast and bacterial activity roughly doubles with every 8°C (14°F) increase in temperature. A dough that takes 10 hours at 20°C will take around 5 hours at 28°C. This is why bakers obsess over dough temperature.

Measure dough temperature, not room temperature. Friction from mixing warms the dough above the ambient temperature — often by 2–4°C. Use a probe thermometer inserted into the centre of the dough. This single habit will make your timing far more predictable.

Target dough temperature for most home bakers: 24–26°C (75–79°F). This gives a manageable 4–6 hour window with 20% starter in white flour.

How Starter Percentage Affects Bulk Time

Starter percentage is the weight of starter as a proportion of total flour. Most recipes use 10–25%.

More starter = more yeast and bacteria from the start = faster fermentation. Halving your starter percentage approximately doubles your bulk time at the same temperature.

This is useful to know when planning bakes:

• Use 20–25% starter for a 4–6 hour same-day bulk
• Use 10–15% starter for a 6–10 hour bulk with more flexibility
• Use 5–8% starter for a long overnight bulk at room temperature

Reading Dough Signs: How to Know When Bulk is Done

The time estimate is a starting point. The dough itself tells you when it’s ready. Look for all four of these signs together:

1. Volume Increase

A 50–75% increase in dough volume is the target for most white flour formulas. More than 75% risks over-fermentation; less than 50% and the dough is likely underproofed.

Use a straight-sided, flat-bottomed container (a square Cambro or a cylindrical dough bucket) and mark the starting level with a rubber band or tape. This makes volume tracking accurate and easy.

2. Surface Appearance

A properly fermented dough has a slightly domed or convex surface — gently bulging upward rather than sitting flat. You’ll see small bubbles breaking through the surface. The sides of the container will show visible bubbles tracking through the dough.

3. The Jiggle Test

Pick up the container and give it a gentle shake. Well-fermented dough jiggles loosely and moves as a single wobbling mass — like a just-set jelly. Under-fermented dough feels stiff and barely moves. Over-fermented dough is so loose it sloshes.

4. Dough Feel

Wet your hand and pull a piece of dough from the edge. It should stretch easily without tearing and feel airy and extensible — you’ll feel small bubbles as you stretch it. If it tears immediately, gluten is either underdeveloped or broken down by over-fermentation.

Troubleshooting Under-Fermentation

Signs: Dough is tight and stiff at shaping, doesn’t spring when poked, tears when shaped. The loaf has poor oven spring, dense crumb, and a thick crust.

Causes:

• Dough temperature too low (measure with a probe thermometer)
• Starter was not active enough at mixing — used too early or too late after feeding
• Starter percentage too low for the conditions

Fix for next bake: Measure actual dough temperature. If it’s below 22°C, find a warmer spot or use warmer water in the dough. Check that your starter is at peak when you mix it in.

Fix mid-bake: If you catch it early, give the dough more time in a slightly warmer spot. If you’ve already shaped and it feels tight, let it final-proof at room temperature for longer than usual before baking.

Troubleshooting Over-Fermentation

Signs: Dough is extremely slack and sticky at shaping, spreads rather than holding shape, tears when you try to build tension. The baked loaf is flat, dense, and may have a gummy crumb.

Causes:

• Bulk ran too long
• Dough temperature spiked during fermentation (common in summer)
• Starter percentage too high for the conditions

Fix for next bake: Reduce bulk time, lower dough temperature (use cooler water), or reduce starter percentage.

Fix mid-bake: If the dough is clearly over-fermented, do not try to fold and recover it. Shape immediately and gently, skip extended final proof, and bake straight away or cold retard in the fridge for 30–60 minutes to firm it up slightly before scoring. The loaf won’t be your best, but it may still be edible.

Stretch and Fold During Bulk

Most sourdough recipes include stretch and fold sets during bulk fermentation — typically every 30 minutes for the first 2–3 hours. This isn’t about degassing the dough (like punching down in yeasted bread); it’s about building gluten strength.

During a stretch and fold, wet your hand, grab one side of the dough, stretch it up as far as it will go without tearing, and fold it over the top. Rotate the bowl 90° and repeat — four folds total completes one set.

The dough becomes noticeably stronger and more elastic with each set. By the third or fourth set, it should hold its shape clearly when lifted. After the final fold, leave the dough undisturbed for the remainder of bulk.

Cold Bulk Fermentation

Many recipes describe a room-temperature bulk followed by a cold final proof (shaping, then refrigerating overnight). But some bakers extend bulk itself into the fridge — a “cold bulk.”

Cold bulk (4°C) slows fermentation dramatically but doesn’t stop it. The dough continues fermenting — just 5–10× more slowly than at room temperature. This gives bakers enormous scheduling flexibility.

If you’re doing a cold bulk, reduce your estimated room-temperature time by around 60–70%, shape the dough, then refrigerate for 8–24 hours. Final-proof at room temperature for 1–2 hours before baking.

FAQs

Can I put my dough in the fridge during bulk? Yes. Putting dough in the fridge during bulk slows fermentation significantly. If you need to pause a room-temperature bulk — for example if it’s running ahead of schedule — refrigerating for 1–2 hours can buy you time without harming the dough.

How do I know if my starter was active enough at mixing? If your starter was at or near peak when you mixed it in, you should see bubbles forming in the dough within 30–60 minutes at 24°C. If there’s no activity after 2 hours, your starter may have been underripe or overripe. Active starter is the foundation — use it at peak.

My dough didn’t rise at all after 8 hours. What happened? Most likely causes: starter was not active (check if it doubles after feeding), dough temperature too low (below 18°C fermentation slows dramatically), or salt was added directly to the starter before mixing (salt inhibits yeast — always mix salt in separately or at least after the starter is incorporated).

Does bulk fermentation time change if I add inclusions like seeds or nuts? Not significantly. Inclusions affect dough strength and shaping more than fermentation speed. The main exception is adding sugar (speeds up fermentation slightly) or fat (slows it slightly by coating the yeast).

Why do some recipes say “bulk until doubled” and others say “don’t let it double”? It depends on the formula, hydration, and flour. High-hydration doughs with strong flour can handle more fermentation. Weaker flours or very wet doughs can overproof before doubling. Always combine volume rise with the jiggle test and surface appearance rather than relying on a single metric.

How does the bulk fermentation calculator work? The bulk fermentation calculator takes your dough temperature, starter percentage, and flour type and outputs an estimated time range. It uses the same temperature-activity relationships that experienced bakers use — a practical starting point that you refine by reading your specific dough.