Sourdough
About Bulk Fermentation
Bulk timing depends on temperature and starter strength, not a single clock time. The checklist on the guide follows the Bulk-O-Matic idea from The Sourdough Journey: judge the dough, then shape.
How the estimate works
- Regular — Hours come from The Sourdough Journey dough-temperature chart. If your dough °F falls between two rows, we linearly interpolate hours between those rows. Rise % and notes use the nearest chart row.
- Advanced — Starts from that same chart time at your dough temperature, then multiplies by a relative factor from hydration, starter %, room temperature, and (when dough is cold) an extra term. At 75% hydration, 20% starter, and 72°F room, the factor is 1, so Advanced matches Regular.
Estimates align best near ~20% starter and typical room-temperature workflows. A very active starter may finish sooner than the number shown.
Bulk-O-Matic PDF (The Sourdough Journey) →Advanced: hours and relative factor
The multiplier is implemented in this app; it is not copied verbatim from the PDF. It is chosen so baseline inputs match the chart, and each knob nudges time in a plausible direction.
Core relationship
Relative factor
Where these values come from
- 75% hydration, 20% starter, 72°F room are the app's fixed baselines. Plugging those in makes every factor equal 1, so Advanced reproduces Regular — by design.
- Hydration uses a small linear bump around 75%: wetter dough tends to ferment a bit faster, so we nudge hours up or down.
- 20 / starter% scales inversely with inoculation: more starter means more fermentation power, so estimated hours shrink.
- Room temperature is measured vs 72°F. Warmer ambient air usually speeds bulk, so it enters the denominator. max(0.5, …) caps the effect so very warm rooms don't collapse the estimate.
- Cold dough (< 60°F) adds coldFactor: a small per-degree lift below 60°F (0.02 per °F is a heuristic, not a physical constant).
The nine checks
The same Bulk-O-Matic cues appear on the guide as a checklist you can tick during bulk. Open the interactive checklist →
Quick reference (also available offline or when printing this page):
1Temperature
Warmer dough ferments faster; cooler dough needs longer. Aim for a steady band (often around 75–82°F) when you can.
2Time
Use the calculator as a window, then confirm with the cues below.
3Percentage rise
Volume increase is one of the most useful signals. Strong flour often lands around 30–50%; weaker flour may need less.
4Domed shape
The surface should dome slightly—edges falling away from the center—not flat or collapsed.
5Bubbles (top)
Scattered surface bubbles are normal; a solid sheet of foam can mean you have gone too far.
6Bubbles (sides)
In a clear bowl you should see uneven gas pockets through the sides.
7Wobble test
Shake the bowl: the mass should jiggle like jelly when it is aerated enough.
8Tactile / sticky
Wet finger: tacky like a sticky note, not soupy. It should let go of the bowl cleanly when ready.
9Smell
Mild, sweet, or yogurt-like is fine. Sharp alcohol or acetone usually means over-proofed.
Aliquot jar
After mixing, put about 40 g of dough in a straight-sided jar and mark the height. Tracking rise in a small cylinder is easier than eyeballing a big bowl; when the sample hits your target, the main dough is usually in the same ballpark.