Bulk fermentation sourdough: a temperature and inoculation chart

Bulk fermentation is the dough's first rise, from the end of mixing until you divide it. This bulk fermentation sourdough chart sets the target by dough temperature and inoculation: about four hours at 78°F with 20% starter, six and a half at 68°F. Judge the end point by percentage rise, not the clock.

What bulk fermentation is, and where it ends

Bulk is the stretch of time the dough spends as a single mass, from the end of mixing to divide and preshape. Stretch and folds, coil folds, and lamination all happen inside it. This is where the wild yeast makes most of the gas the loaf will hold, and where the bacteria make most of the acid that flavors it.

The end point is a state, not a clock reading: enough gas trapped for oven spring, enough acid for flavor, and not so much enzyme activity that the gluten gives up.

Two variables set the sourdough bulk fermentation time

Dough temperature, not room temperature. Mixing adds friction heat, cold flour drops it, and a bowl sitting on a stone counter sheds a degree or two an hour. An instant-read probe pushed into the center of the dough is the highest-value tool in this whole process. Take a reading right after mixing, then again a couple of hours in.

The working rule: fermentation speed roughly doubles for every 15°F (about 8°C) rise in dough temperature. It's a rule of thumb rather than a law, and it under-predicts how sluggish a dough gets below 70°F, but the mental model is right. Ten degrees isn't a tweak — it's most of your schedule.

Inoculation is the weight of starter as a percentage of the flour, written the same way hydration is written as a baker's percentage. Put 100g of starter into a dough with 500g of flour and you're at 20%.

The bulk fermentation sourdough chart

Times assume a white or lightly whole-grain dough at 70–75% hydration, 2% salt, with a mature starter used at peak. Read down to your dough temperature, across to your inoculation.

Dough temp	5% starter	10% starter	20% starter
68°F / 20°C	12–14 hr	9–10 hr	6–7 hr
70°F / 21°C	11–12.5 hr	8–9 hr	5.5–6.5 hr
72°F / 22°C	10–11.5 hr	7–8.5 hr	5–6 hr
74°F / 23°C	9–10.5 hr	6.5–7.5 hr	4.5–5.5 hr
76°F / 24°C	8.5–9.5 hr	6–7 hr	4–5 hr
78°F / 26°C	7.5–8.5 hr	5.5–6 hr	3.5–4.5 hr
80°F / 27°C	7–8 hr	5–5.75 hr	3.25–4 hr
82°F / 28°C	6.25–7.25 hr	4.5–5.25 hr	3–3.75 hr
Target rise	~100%	~75%	~50%

Two things about this sourdough bulk fermentation temperature chart. The times are a starting bracket, not a promise — your flour, your starter, and your kitchen will pull them around. And the bottom row matters more than everything above it, because the rise is the number you actually measure.

The chart only becomes a schedule once you write the numbers down: dough temperature at the end of mixing, the time bulk started, and each rise reading. If you'd rather not keep that on paper, Sourdough Tracker is a sourdough baking companion app for iPhone.

Percentage rise beats "let it double"

"Let it double" is inherited from commercial-yeast baking, where the yeast makes gas and almost nothing else. Sourdough makes gas and acid at the same time, and the acid is what eventually degrades the gluten. So the useful question isn't how far the dough has expanded — it's how much fermentation has happened. Expansion is only a proxy.

Inoculation is what breaks the proxy. A 20% dough starts with four times the microbial population of a 5% dough working through the same flour, so it reaches the same degree of acidification much earlier in its expansion. Wait for it to double and you've gone well past. A 20% dough is usually ready nearer 50% rise; 10% lands around 75%; only at 5% or below does "double" become roughly correct.

That's why two bakers can both be right and still disagree. They're running different inoculations.

The aliquot jar: measure the rise instead of eyeballing it

A rise percentage is useless if you can't see it. Bowls are the problem: they're tapered, so a real gain in volume looks like far less height change, and dough smears up the sides where it's hard to read.

The aliquot jar fixes that:

1. Right after mixing, while the dough is still uniform, pinch off a piece about the size of a golf ball.
2. Drop it into a small straight-sided jar. A tapered jar or one with shoulders will lie to you.
3. Press it flat with a wet finger so the top is level.
4. Mark the starting height with a rubber band. Add lines at 25%, 50%, 75%, and 100% above it to read at a glance.
5. Keep the jar beside the bulk container so both stay at the same temperature.

Rise then reads straight off the wall. The main dough gets folds and the aliquot doesn't, which barely matters — folds redistribute gas, they don't change how fast fermentation runs. Do keep the jar out of drafts and sunbeams, though: a small piece of dough in glass changes temperature much faster than a covered tub.

Four cues that say bulk is done

Read these alongside the jar, not instead of it.

Dome. The surface is convex and holds that curve. A dough gone flat, or domed and then sunk in the middle, is past.

Jiggle. Shake the container gently. Finished dough wobbles as one mass, the way set custard does. Under-fermented dough barely moves; over-fermented dough ripples separately from the container.

Bubbles at the edge. Through the side of a clear tub you should see bubbles of several sizes against the wall, plus a scatter domed under the surface. All tiny and uniform means more time. Huge, thin-walled bubbles collapsing as you watch means too much.

Release from the sides. The dough pulls cleanly away from the walls instead of gripping them, and feels airy and slack rather than dense and tacky.

Smell is a fifth cue worth learning. Finished bulk smells yeasty and faintly tangy. Sharp acetone or nail-polish notes mean it's well past.

What shifts the numbers

• Whole grain. Whole wheat, rye, and spelt bring more enzyme activity, more minerals, and more of their own microbes. Anything over about 20% whole grain runs noticeably faster than the chart. Rye is faster still.
• Hydration. Wetter dough ferments a little quicker and shows its rise more clearly. A stiff dough at 65% takes longer and hides it better.
• Salt. Salt slows fermentation. At 2% of flour weight the chart holds; at 2.5%, add time.
• Starter condition. A starter used at peak behaves differently from one used four hours after peak. If yours has been sluggish, feeding ratios and feed timing are the first thing to fix, and the float test is a rough check that it's ready to use.
• Batch size. A large mass of dough holds its own heat and can run a degree or two above the room. A single small loaf in a wide tub tracks the room almost exactly.

Reading the finished loaf backwards

The bake tells you what bulk actually did.

Under-fermented: tight, dense crumb; a tunnel or tight ring under the top crust; gummy texture; pale flavor; dough that fought you during shaping. Add time or warmth next round.

Over-fermented: dough that spread instead of standing during proof, slack and sticky on the bench, little oven spring, a flat wide loaf, irregular crumb with weak papery walls, sour past what you wanted. Cut time or temperature, or drop the inoculation.

Both are the same equation solved at the wrong temperature.

FAQ

How long is bulk fermentation?

Roughly 3 to 14 hours, depending almost entirely on dough temperature and inoculation. A 20% inoculation at 78°F lands near four hours; the same dough at 68°F takes six to seven; a 5% inoculation at 68°F can run overnight. Use the chart as a starting bracket and correct it from your own bakes.

How to tell when bulk fermentation is done

Measure the rise in an aliquot jar and check the physical cues at the same time. Stop near 50% rise for a 20% inoculation, 75% for 10%, and about 100% for 5% — provided the dough also domes, jiggles as one mass, shows mixed-size bubbles at the edges, and releases from the sides of the container.

What should sourdough look like after bulk fermentation?

Domed rather than flat, visibly lighter and airier, with bubbles of mixed sizes against the walls of a clear container and a few pushing up under the surface. It should pull away from the sides cleanly and wobble in one piece. A flat, sunken, soupy surface means it went too long.

Can I bulk ferment sourdough in the fridge?

You can, but it's slow and uneven. A refrigerator takes hours to bring a warm dough down, so the outside stalls while the center keeps working. Most bakers run bulk at room temperature and move the dough to the fridge for the final proof, where the cold does more useful work on flavor and handling.

Does the aliquot jar rise at the same rate as the dough?

Closely enough to be useful, as long as it sits beside the main dough at the same temperature and the sample was taken once the dough was uniform. The small piece responds to temperature swings faster, so a jar left in a draft will read wrong.