How Long to Bulk Ferment Sourdough in a Cold 68 Degree (68°F / 20°C) Kitchen (18% Starter)
Q10=0.59x metabolic curve for 90g starter per 500g flour at 68°F (20°C): stop at 6.36 cm bowl height (+75% aliquot rise).
Baking at 68°F (20°C) with 18% inoculation (90g starter/500g flour) sets a 8.1–9.7 hour bulk clock before core cooling past 43.8°F. Aim for +75% true volumetric expansion (+59% vertical height rise in a sloped bowl to 6.36 cm) and avoid the +114% volume explosion of doubling height.
- Estimated Bulk Time
- 8.1–9.7 hrsAt 68°F (20°C) with 18% starter (Q10=0.59x)
- Target Aliquot Volume Rise
- +75%Capped volumetric cutoff (<43.8°F dormancy)
- Sloped Bowl Height Target
- 6.36 cm+59% vertical climb from 4.0 cm
- 2x Height Trap Warning
- +114% VolCoil fold every 39m (LAB 4.2:1)
Bulk Fermentation Time & Bowl Geometry Matrix Around 68°F (20°C) & 18% Starter
5-point neighborhood comparison around 68°F (20°C) and 18% starter (90g/500g flour), showing window hours, conical height rise %, straight-wall volume rise %, and 39-min coil fold intervals.
| Temp & Levain Seed (Around 68°F / 18%) | Fermentation Window | 9" Conical Height Rise | Straight-Wall Volume Rise | Coil Fold Cadence |
|---|---|---|---|---|
| 66°F (18.9°C) @ 16% (80g) Cooler / Lower Seed | 10–13 hrs (600–780m) | +68% height (4.0 → 6.72 cm) | +75% vol (2x trap: +137.1%) | Every 42 min (Row 1) |
| 68°F (20°C) @ 16% (80g) Baseline Temp / Lower Seed | 8.9–10.6 hrs (534–636m) | +59.3% height (4.0 → 6.37 cm) | +75% vol (2x trap: +114.6%) | Every 39 min (Row 2) |
| 68°F (20°C) @ 18% (90g) [Current Target] | 8.1–9.7 hrs (486–582m) | +59% height (4.0 → 6.36 cm) | +75% vol (2x trap: +114%) | Every 39 min (Row 3) |
| 68°F (20°C) @ 21% (105g) Baseline Temp / Higher Seed | 7.2–8.7 hrs (432–522m) | +58.6% height (4.0 → 6.34 cm) | +75% vol (2x trap: +113%) | Every 37 min (Row 4) |
| 70°F (21.1°C) @ 21% (105g) Warmer / Higher Seed | 6.3–7.7 hrs (378–462m) | +53.6% height (4.0 → 6.14 cm) | +72.3% vol (2x trap: +101%) | Every 35 min (Row 5) |
On-Bench Hydration & Fermentation Adjuster
Modify base flour mass, levain inoculation, or ambient kitchen temperature below to recalculate from this 8.1–9.7 hrs baseline.
Why a Cool 68°F (20°C) Kitchen Caps Bulk at +75% Rise (6.36 cm)
Symbiotic lag-phase duration for 18% starter (90g/500g flour) at 68°F (20°C) is governed by a 0.59x thermal multiplier and a 4.2:1 lactic/acetic trajectory. Once the dough climbs +59% vertically to 6.36 cm (+75% aliquot volume) between 8.1 and 9.7 hours, yeast dormancy must be induced below 43.8°F.
Calorimetric cooling curves from 68°F (20°C) to 43.8°F show residual CO2 generation proportional to 18% inoculation and 0.59x Q10 momentum. Cutting off bulk after 8.1–9.7 hours (39-min fold intervals) at +59% sloped-bowl height (6.36 cm / +75% volume) guarantees peak oven spring.
4-Stage Bench & Cold-Retard Protocol for 68°F Dough at 18% Starter
- Seed & Thermal Check (68°F / 20°C): Verify dough core reads 68°F after incorporating 90g active levain (18% baker's math) for a 4.2:1 LAB balance.
- Aliquot & Sloped Vessel Setup: Place 40g dough in a straight cylinder (mark +75%) and set a ruler at 6.36 cm (+59% climb) on your 24 cm sloped bowl.
- Gluten Alignment (39-Min Intervals): Perform gentle folds every 39 minutes without degassing; stop folding 90 minutes before hour 8.1.
- Bench Preshape & 38°F Retard: Dump onto the bench between 8.1 and 9.7 hours at +75% rise, tension-roll, and refrigerate immediately until core drops past 43.8°F.
Common Scaling & Troubleshooting Questions (8.1–9.7 hrs)
What percentage rise should I look for at 68°F (20°C) with 18% levain?
Target +75% true volumetric expansion (+59% vertical height rise in a sloped bowl, from 4.0 cm to 6.36 cm) before 38°F cold retarding, avoiding the +114% volume explosion of doubling height.
How do I adjust 68°F bulk time if I drop starter from 18% to 16%?
Reducing inoculation from 18% to 16% at 68°F (20°C) extends the 8.1–9.7 hr bulk window while keeping the same +75% volumetric (6.36 cm height) shaping target.
How often should I do coil folds at 68°F with 18% starter?
Space your coil folds every 39 minutes during the first half of the 8.1–9.7 hour window at 68°F (20°C) so the gluten network holds its +75% rise.