🌡️ Hydration also affects your bulk time.
Higher hydration doughs ferment faster at the same temperature. The sourdough calculator shows you your exact hydration percentage before you start.
Every sourdough recipe gives you a bulk fermentation time. Almost none of them will be correct for your kitchen.
The time printed in a recipe is based on the recipe developer's kitchen temperature, their starter activity, and their flour. Change any of those variables — and your kitchen temperature is almost certainly different from theirs — and the time shifts. Sometimes by hours.
Understanding why temperature drives bulk fermentation time, and having a reference chart for your actual kitchen, is more useful than any single recipe's timing.
Why Temperature Controls Everything
Bulk fermentation is driven by microorganisms — primarily wild yeast (Saccharomyces cerevisiae and related species) and lactic acid bacteria (Lactobacillus and others). Both are living organisms whose metabolic rates are directly governed by temperature.
The doubling rule: For every 10°F (5.5°C) increase in dough temperature, fermentation activity roughly doubles. For every 10°F decrease, it roughly halves. This relationship isn't perfectly linear, but it's accurate enough to use as a planning rule.
This means:
- Dough at 78°F ferments approximately twice as fast as the same dough at 68°F
- A recipe that says "4–5 hours" at 76°F will need 8–10 hours in a 66°F kitchen
- A kitchen that runs 74°F in winter and 80°F in summer will have bulk times that vary by 3–4 hours for the same recipe year-round
Dough temperature vs room temperature: These are not the same. Cold flour from the pantry, cold water from the tap, and a cold mixing bowl can all produce dough that is several degrees colder than your room. Conversely, dough sitting near a warm oven, in a turned-off oven with the light on, or in a proofing box will be warmer than the room.
Measure the dough temperature, not the room. An instant-read thermometer inserted into the center of the dough gives you the number that actually determines your timeline.
The Bulk Fermentation Temperature Chart
This chart uses 15-20% starter at peak activity as the baseline. Adjust for starter percentage using the modifier in the next section.
| Dough temp °F | Dough temp °C | Bulk time 15-20% starter | Notes |
|---|---|---|---|
| 62–65°F | 17–18°C | 10–14 hrs | Very slow. More acetic acid development — complex, sharper flavor. Overnight at room temp in cold kitchen. |
| 66–68°F | 19–20°C | 8–12 hrs | Slow fermentation. Good for starting bulk in the evening and shaping in the morning. More sour than warmer ferments. |
| 69–72°F | 21–22°C | 6–9 hrs | Moderate pace. The most common home kitchen range. Balanced lactic/acetic acid profile. |
| 73–76°F ⭐ | 23–24°C | 4–7 hrs | Sweet spot for most bakers. Active fermentation, manageable timing window, good flavor development. |
| 77–80°F | 25–27°C | 3–5 hrs | Fast. Check frequently. More lactic acid (milder flavor). Summer kitchens often land here. |
| 81–84°F | 27–29°C | 2–3.5 hrs | Very fast. Difficult to catch at the right moment without checking every 30 minutes. Risk of over-fermentation rises sharply. |
| 85°F+ | 29°C+ | 1.5–2.5 hrs | Problematic range. Fermentation is so fast that most bakers cannot catch it at the right point. Consider cooling water, cold flour, or refrigerating the dough partway through. |
How to use this chart
Take your dough temperature at the start of bulk fermentation. Find the row. Use the lower end of the time range as your first check-in time — start looking at the dough then, but don't expect it to be done. Use the poke test and visual signs (below) to confirm, not the clock.
Starter Percentage Adjustment
The chart above uses 15-20% starter. If your recipe uses a different percentage, adjust:
| Starter % | Adjustment to chart times | Example at 75°F |
|---|---|---|
| 5–8% | Add +2-4 hrs | 6-10 hours instead of 4-7 |
| 10–12% | Add +1-2 hrs | 5-8 hours instead of 4-7 |
| 15–20% ⭐ (chart baseline) | No adjustment | 4-7 hours |
| 25–30% | Subtract -1-2 hrs | 3-5 hours instead of 4-7 |
Why starter percentage matters: More starter means more lactic acid bacteria and yeast cells are active at the start of fermentation. With more organisms working, the acidification and gas production happen faster. A 5% levain recipe is specifically designed to be a long, slow ferment — often overnight. A 25% levain recipe is designed for speed.
The Three Signs That Bulk Is Done
The chart gives you a window. These signs confirm you're at the right point within that window.
Sign 1 — Volume increase
The dough should have increased by 50–75% in volume. Not doubled — that's a common misquote. At 50% increase, the dough has risen noticeably but still has structure. A true doubling usually means over-fermentation, especially at warmer temperatures.
Practical tip: mark the starting level on your container with a rubber band or a piece of tape. This makes volume tracking simple and removes guesswork.
Sign 2 — Surface and texture changes
Properly fermented dough has a domed, slightly rounded surface — not flat, not collapsed. You may see small bubbles on the surface or visible through the walls of a clear container. When you gently shake the bowl, the dough should jiggle slightly — this "wobble" is evidence of gas production throughout the dough.
The dough should feel lighter and more airy than when you started, and slightly tacky rather than stiff.
Sign 3 — The poke test
Wet your finger and poke the dough about 0.5 inch (1.3cm) deep. Watch what happens to the indent:
- Springs back quickly and fully → needs more time. The gluten is still tight and fermentation hasn't generated enough gas yet.
- Springs back slowly, about halfway, over 3–5 seconds → ready to shape. This is the target.
- Doesn't spring back, indent stays → over-fermented. The gluten has weakened. Shape immediately and consider a shorter final proof.
The poke test behavior changes as temperature changes — cold dough springs back more slowly than warm dough at the same fermentation stage. If you're checking cold dough, allow slightly more time for the indent to respond before interpreting.
For a complete walkthrough of the poke test, see Sourdough Poke Test: How to Read Your Dough at Every Stage.
How Hydration Affects Timing
Higher hydration doughs (78%+) ferment slightly faster than lower hydration doughs at the same temperature. The extra water provides a more mobile environment for bacteria and yeast — they can move through the dough more easily, and there's more dissolved oxygen and sugars available.
The difference is meaningful but not dramatic: a 80% hydration dough may finish bulk 30–60 minutes faster than a 68% hydration dough at the same temperature, with the same starter.
More practically: high hydration doughs show less obvious visual rise because the weaker gluten structure doesn't trap gas as efficiently. Don't rely on volume alone for high hydration doughs — the poke test becomes more important.
For your recipe's hydration percentage, use the Sourdough Hydration Calculator.
What Goes Wrong: Under vs Over Fermentation
Both failure modes are recoverable — if you catch them at the right time.
Under-fermented dough
What it looks like: Dough that hasn't risen much, feels dense and stiff, and has a tight, bouncy response to the poke test.
What the loaf does: Poor oven spring (the loaf doesn't open along the score, or barely rises in the oven). Dense, gummy crumb — particularly in the center. Pale crust because there's less sugar remaining for Maillard browning.
Recovery: If you catch it before shaping — return to warm environment and continue. Check every 30–60 minutes. If you've already shaped and cold proofed, bring the shaped loaf to room temperature for 30–60 minutes before baking to give it more time.
Over-fermented dough
What it looks like: Dough that's very slack and sticky, tears when you try to stretch it, and collapses rather than springs back on the poke test. May smell strongly of alcohol.
What the loaf does: Spreads flat during shaping and final proof rather than holding its form. Bakes into a flat, dense loaf with very open, irregular crumb and an intensely sour flavor that most people find unpleasant.
Recovery: If mildly over-fermented — shape gently (don't degas), cold proof immediately in the refrigerator, and bake without extended room temperature proofing. The cold will slow further fermentation. Significantly over-fermented dough bakes poorly as a loaf — use for discard focaccia, pizza dough, or flatbreads where structure matters less.
Temperature Control Strategies
Summer — dough is too warm:
Use cold water (even ice water) when mixing. Store flour in the refrigerator overnight before baking. Begin bulk fermentation in the coolest room in your house. Use a shorter bulk time and move to cold proof in the refrigerator earlier.
Winter — dough is too cold:
Proof in an oven with just the light on (often 75–78°F). Use warm water (not hot — above 95°F will damage the starter) when mixing. Place the dough container on top of the refrigerator where heat from the compressor rises. A proofing box gives consistent temperature year-round if you bake frequently.
Measuring dough temperature accurately:
Insert an instant-read thermometer into the center of the dough mass — not just the surface. The center is often 2–3°F colder than the surface, and it's the center temperature that determines overall fermentation rate. Take readings at the start of bulk and again halfway through if you want to track changes.
My Personal Chart for Texas Summers
My kitchen in summer regularly hits 80–82°F. Using the chart: bulk fermentation at 80–82°F takes 2–3 hours with 20% starter. I start checking at 90 minutes.
The complication: at this temperature, the window between "ready" and "over-fermented" is about 30–45 minutes. I check every 20–30 minutes from 90 minutes onward.
My adjustments for summer baking:
- Use 50°F water from the refrigerator
- Pre-chill the mixing bowl
- Target a post-mix dough temperature of 74–76°F (the cold water and bowl cool the dough)
- This gives me the 4–5 hour window from the 73–76°F row instead of the 2–3 hour window
For winter baking, the same dough at my drafty 66°F kitchen goes 10–12 hours overnight. I start it at 9pm and shape at 7–9am.
What hydration is your recipe?
Higher hydration doughs ferment faster at the same temperature — the calculator shows your exact percentage before you start bulk.
Related Reading
- Bulk Fermentation Sourdough Guide — The complete bulk fermentation method: stretch and folds, timing, and what to look for at each stage
- Sourdough Poke Test — How to read your dough at every stage — the tactile test that overrides the clock
- Cold Proofing vs Room Temperature Proofing — What happens after bulk fermentation and how temperature affects the final proof
- Sourdough Starter from Scratch — Starter activity is the other major variable in bulk timing — a sluggish starter changes everything
- How to Know When Sourdough Starter Is Ready — Confirming starter peak before bulk fermentation begins
