Temperature reference

36–40°F Sourdough (2.20–4.40°C)

Bulk multiplier: 10.000× · Proof multiplier: 10.000× · Activity: dormant

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40°50°60°70°80°90°36–40°Fdormantcoldhot

Dial shows where 36–40°F sits on the sourdough activity scale (32–100°F). Indicator points at the midpoint; color shifts from cool blue (dormant) to warm orange (hyperactive).

Recommendation

Refrigerator territory — used for overnight retard during proofing or bulk slowdown. 12-16 hours at this temperature is equivalent to 1-1.5 hours at 76°F baseline. Essential for flavor development in artisan sourdough. Cold retard improves shape retention, enables flexible scheduling, and develops deeper tangy flavors. Place dough in floured banneton, cover, refrigerate at this temperature.

Timing calculator at this temperature

Multiplier at 38°F
2.9×
Adjusted bulk ferment
11.6 h
Adjusted final proof
34.8 h
How the math works

Multipliers are piecewise-linear interpolations between reference points measured by Myhrvold et al. in Modernist Bread vol 3. 76°F is the baseline (1.0×); every 10°F drop roughly doubles fermentation time, and every 10°F rise roughly halves it.

How each style behaves at this temperature

Click any style to see its full timing at 36–40°F:

Related references on this site

The gear that makes the math work

A short, honest baking kit. The scale matters most — every weight on this page is in grams. The Dutch oven is what turns a good crumb into a great crust.

  • Digital kitchen scale (0.1 g)

    Baker's percentage is by weight, not volume — a 0.1 g scale is what makes the math on this page accurate.

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  • Dutch oven / combo cooker

    Traps steam for the first bake phase — the single biggest factor in oven spring and a blistered, glossy crust.

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  • Banneton proofing basket

    Wicks moisture and holds shape during the final proof, so high-hydration dough doesn't spread flat.

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  • Bread lame + bench scraper

    A sharp lame scores clean ears; a steel bench scraper handles wet, sticky dough without tearing the gluten.

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  • High-protein bread flour

    The math assumes ~12–14% protein. Real bread flour absorbs the hydration you calculate — all-purpose won't.

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  • Danish dough whisk

    Mixes shaggy, high-hydration dough in seconds without the gluey mess of a spoon or your hands.

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🎧 Or learn the craft by ear

The numbers here are the what; a good baking book is the why. An Audible trial gets you any title free — Michael Pollan’s Cooked(the “Air” chapter is the best story ever told about why bread rises) is a perfect first listen.

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