Temperature reference

63–67°F Sourdough (17.20–19.40°C)

Q: How does a 63-67°F kitchen affect sourdough?

Bulk multiplier 1.500× and proof multiplier 1.550× relative to the 76°F baseline. Starter activity: moderate. Cool kitchen — spring/fall without heating, air-conditioned summer. Ferment 1.5× longer than baseline. Good flavor development territory. Dough develops more complex sour notes. Manageable schedule. Extend bulk and proof by 50% vs recipe defaults.

Bulk multiplier: 1.500× · Proof multiplier: 1.550× · Activity: moderate

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Dial shows where 63–67°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

Cool kitchen — spring/fall without heating, air-conditioned summer. Ferment 1.5× longer than baseline. Good flavor development territory. Dough develops more complex sour notes. Manageable schedule. Extend bulk and proof by 50% vs recipe defaults.

Timing calculator at this temperature

Bulk (at 76°F)(h)

Proof (at 76°F)(h)

Your kitchen temp(°F)

Multiplier at 65°F: 1.9×
Adjusted bulk ferment: 7.6 h
Adjusted final proof: 22.8 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 63–67°F:

Guide: temperature and time in sourdough — the piecewise-linear multipliers and how to use them in planning
Autolyse strategy by temperature — warmer kitchen needs shorter autolyse before adding starter
Levain build timing — how long to wait before peak in a hot vs cold kitchen
All 25 recipes — each has a /timing page — each recipe shows bulk + proof at 63-67°F
All 12 hydration levels — drier doughs ferment slower; combine hydration choice with temperature
All 8 temperature ranges — from cold retard 38-40°F to peak summer 88-95°F

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.

Start a free Audible trial →

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Gear guides — what actually matters

Recommendation

Timing calculator at this temperature

How each style behaves at this temperature

Related references on this site

The gear that makes the math work