3 Bulk Fermentation Charts, Checked Against Real Dough at 63°F

Tested By LAB Nathan

Reviewed By HACCP Nouhayla A.

Protocol Updated: Oct 25, 2026

Published bulk fermentation charts stop at 65 to 66°F, so a 63°F kitchen falls off the page. fond.kitchen lists 8 to 12 hours at 65 to 68°F. Our sourdough at 63°F needed 11.8 hours to rise 60%. Add about 5% to the chart time for every degree below 66°F. Bulk fermentation is the first rise, from mixing until shaping.

Key findings from The 2026 Cold Bulk Check

1. None of the 3 charts lists a dough temperature below 65°F.
2. At 63°F (17.2°C), our sourdough needed 11.8 hours to reach a 60% rise.
3. Each degree below 66°F added about 5% to the time.
4. Rise percentage was a better stop signal than the clock.

The 3 charts at a glance

Your kitchen reads 63°F, and every chart you open starts at 65 or 66. This check belongs to our map of long rises in a cold kitchen, measured at 62 to 64°F. Here’s what we measured, side by side, over two runs at each temperature.

What does a bulk fermentation chart tell you?

A bulk fermentation chart pairs a dough temperature with a time range and a target rise. Dough temperature sets the pace, not room temperature. A probe thermometer in the center of the dough gives that number. The sourdough table from fond.kitchen, updated September 2, 2026, is typical:

• 65–68°F (18–20°C): 8–12 hours
• 70–73°F (21–23°C): 6–8 hours
• 75–78°F (24–26°C): 4–6 hours
• 80–84°F (27–29°C): 3–4 hours

Its finish line is a 50–75% rise in volume. During that window, wild yeast makes carbon dioxide, and gluten traps the gas. The starter’s lactic acid bacteria, tiny microbes that sour the dough, make lactic acid and acetic acid. Those acids lower the pH and build flavor.

One detail surprised us. The same page prints a second table with 6–10 hours for the 65–68°F band. Two ranges for one band show how loose chart times are. The rise target travels better than the clock, from one kitchen to the next.

How did we check 3 charts against real dough?

We built one lean sourdough and ran it twice at each kitchen temperature. The formula uses baker’s percentages, where each ingredient is a share of the flour weight. Each batch held 500 g bread flour and 375 g water, or 75%. It added 100 g active starter (20%) and 10 g salt (2%).

Our team held the kitchen at 62, 63 and 64°F during sessions in October and November 2026. An aliquot jar tracked the rise. That is a small straight-sided jar holding a sample of the same dough, with a rubber band marking the start. A ThermoWorks Thermapen probe read the dough’s core every hour. A phone photo logged each hourly mark.

We stopped bulk at a 60% rise in the jar. Then we shaped each loaf into a banneton, a ridged proofing basket. The limits are real: one starter, one flour, six runs. Your starter may run faster or slower, usually in the same proportion at every temperature.

What do the 3 charts say about a cold kitchen?

All 3 charts stop at 65°F or above, so none covers a 62 to 64°F kitchen. Each one looks at the problem from a different angle:

• fond.kitchen gives 8–12 hours at 65–68°F and calls that band fine for an overnight bulk.
• The Sourdough Journey publishes timetables with 20 data points from 66°F to 74°F. Its newer Two-Factor chart reaches 65°F (18°C), with 12–16 hours and a 100% rise. The chart’s recipe sits close to ours: 20% starter, 75% water.
• Maurizio Leo at The Perfect Loaf targets dough at “74 to 76°F” and expects bulk to take “2 to 5 hours.”
• Brod & Taylor, maker of a folding home proofer, places sourdough in a 70–85°F range.

The charts also disagree on the finish line. Targets run from a 20–30% rise for whole grain dough to 100% at 65°F. Times at the coldest row run from 8 to 16 hours. That spread, not the missing row alone, is the real puzzle for a cold kitchen.

How long does bulk fermentation take at 62 to 64°F?

Our sourdough reached a 60% rise in 12.3 hours at 62°F, 11.8 hours at 63°F and 11.2 hours at 64°F. Each figure is the average of two runs. The jar barely moved for the first 4 hours, then climbed fast after hour 8.

Why does one degree matter so much? Biologists use Q10, the factor by which a rate changes over a 10°C (18°F) step. For most living systems, Q10 sits between 2 and 3. Our three temperatures fit a Q10 close to 2.3.

What didn’t go as planned at 10 hours?

We trusted the chart at first and stopped the bulk at 10 hours. The dough had risen only 40 percent. It baked into a dense loaf with a tight crumb. On the next run, we gave it nearly 12 hours at 63°F and waited for a 60 percent rise. Now we read the rise, not the clock.

How much longer should you ferment below 66°F?

Add about 5% to the chart time for every degree below 66°F. The math starts from Q10. A Q10 of 2.3 spread over 18°F gives 1.047 per degree, or 4.7%. Our own runs agree: 62 to 64°F gave 4.8% per degree. The Sourdough Journey timetable, read at 20% starter from 66 to 74°F, implies 5.5%. The fond.kitchen sourdough table implies closer to 7%.

Here is the rule at work:

• A chart that says 10 hours at 66°F becomes about 11.5 hours at 63°F.
• Our 11.8 hours at 63°F maps back to about 10.3 hours at 66°F.
• Three degrees below the floor adds roughly 1.5 hours to a 10-hour bulk.

Keep the limits honest. We checked this rule from 62 to 64°F only. Below 62°F, use it as a starting estimate and let the jar decide. A strong starter shortens every number in the same proportion, so the 5% step still holds.

How do you know when bulk fermentation is done?

Read the rise and the dough together, and check the clock last. These are the signs the dough is ready across our runs and the 3 charts:

• Volume: a 50–75% rise on fond.kitchen, and 60% in our cold runs.
• Movement: the dough “wobbles like jelly” when you shake the container.
• Grain: Maurizio Leo expects whole grain dough to rise “20% to 30%,” while white dough may double.
• Surface: a domed top, with bubbles on the surface and along the sides.
• Two factors: The Sourdough Journey’s Two-Factor Method pairs dough temperature with percentage rise.

In the cold, the starter’s natural cultures work slowly but steadily. The aliquot jar shows that progress hour by hour. A 63°F dough at 40% still has about 2 hours to go, even when the clock already says 10 hours. Tip #1: mark the jar at 60% before you start, then stop when the dough meets the line.

Can you leave sourdough to bulk ferment on the counter overnight?

Yes, at 62 to 64°F an overnight bulk fits. Our dough needed 11 to 12 hours. Start it around 9 p.m., and at 63°F it reaches a 60% rise near 8:45 a.m. Check the aliquot jar when you wake up. At 62°F, add about 30 minutes to that wake-up check.

A warmer room changes the plan. fond.kitchen lists 6–8 hours at 70 to 73°F. By the 5% rule, our dough would hit 60% around 5:30 a.m. at 70°F. That is likely before your alarm.

This applies to lean dough only: flour, water, salt and starter. Milk, eggs or butter change the timing. For a predictable daytime bulk, hold the dough at one steady temperature. We compared a proofing box for steady warmth against four DIY setups. A refrigerator works the other way. At 38 to 41°F, fond.kitchen lists 12 to 24 hours, with the rise slowed to a crawl.

What should you remember about bulk fermentation charts in a cold kitchen?

A bulk fermentation chart is a starting point, not a stop signal. Below 65°F, no published chart gives you a number. Start from the coldest row and add about 5% for each degree below 66°F. At 63°F, plan on roughly 12 hours with a 20% starter. Then let an aliquot jar make the final call.

Stop at a 60% rise for a lean white sourdough. Push higher only if the crumb comes out tight. Record the dough temperature and the hours on every bake. After 2 or 3 bakes, your own kitchen becomes the chart.

Three numbers carry most of the work. A dough at 63°F needs about 11.8 hours with a 20% starter. Each degree below 66°F adds about 5%. A 60% rise in the jar marks the end of bulk for a lean white loaf. Keep those three close to your thermometer this winter.

Map every warm spot in a cold kitchen

Where do these numbers come from?

Every figure on this page traces to one of seven sources. Our own numbers come from The 2026 Cold Bulk Check. The Ovenlytic team ran it in October and November 2026: six runs, three temperatures, one formula. Each time on this page is the mean of two runs, rounded to a tenth of an hour. We quote chart values as each source printed them on the date shown.

1. fond.kitchen, Bulk Fermentation glossary, updated September 2, 2026. Time and rise tables.
2. The Sourdough Journey, Bulk Fermentation Timetables V1.0, December 2022. Over 60 timed batches, 66 to 74°F.
3. The Sourdough Journey, Dough Temperature and Percent Rise Chart V2.0, December 2023. The 65°F row.
4. The Sourdough Journey, Ultimate Sourdough Bulk Fermentation Guide, updated July 27, 2026.
5. Maurizio Leo, The Perfect Loaf, guide to bulk fermentation, updated April 16, 2026.
6. Brod & Taylor, Bread Rising Tips, accessed October 21, 2026.
7. Wikipedia, Q10 temperature coefficient, accessed October 21, 2026.