Sourdough Bake Planner

Tap for the source and reasoning

Q10 is the factor by which fermentation rate multiplies per 10°C. No source states a Q10 for sourdough directly, so it is derived here, and the derivation is ours rather than either source's. Fitting a cardinal-temperature curve to the Tmin/Topt/Tmax values Gänzle et al. publish gives an effective Q10, across the 16-27°C band home bakers actually work in, of 2.4 for L. sanfranciscensis LTH2581, 2.7 for LTH1729 and 2.5 for C. milleri. Weekend Bakery's measured 18-30°C bulk fermentation table independently implies 2.6. The supported range is therefore about 2.4 to 2.7, and 2.4 is retained as the low end, which makes the model extrapolate less aggressively away from the 21°C anchor. The widely repeated rule that fermentation "doubles every 5°C" implies a Q10 of 4 and is rejected: it contradicts the time-temperature table published by the very source that states it.

Tap for the source and reasoning

Midpoint of the conventional 20-22°C room-temperature band, and the anchor all reference timings are quoted at. It is deliberately an ambient kitchen temperature rather than an optimum: Hamelman puts the best dough temperature several degrees higher, at 24-26°C. The anchor only needs to be a temperature a baker can recognise and measure in their own kitchen; the Q10 curve moves the timings away from it.

Tap for the source and reasoning

Sits inside the 0-5°C range UK guidance advises and just under the 40°F (4.4°C) ceiling used in US guidance, so it represents a correctly set domestic fridge under both. No timing is derived from it: 4°C is far below the model's 16°C validity floor, and below even the 8.0 ± 1°C minimum growth temperature the Q10 citation reports for Candida milleri, so the equation is never evaluated there. It is recorded because it is the temperature at which cold retard actually happens, and it is what places retard outside the model. Real domestic fridges vary by several degrees between shelves and are frequently warmer than their dial claims, which loosens cold-retard timing further.

Tap for the source and reasoning

The equation is a constant-Q10 fit inferred over roughly 16-27°C, and it is applied from 16°C to 32°C. The floor is the bottom of the band the Q10 was inferred over, which is the only floor the citation supports. Below it fermentation slows faster than any fixed coefficient describes, because the organisms approach their minimum growth temperatures: Candida milleri, the yeast whose gas raises the dough, stops growing at 8.0 ± 1°C, and at a minimum growth temperature the time to ferment is not long but infinite. Fitting a cardinal-temperature curve to the paper's own values — our inference, not the authors' — makes that concrete: the effective Q10 of such a curve is about 2.7 between 16 and 26°C, about 13 between 12 and 22°C, and about 86 between 10 and 20°C. A single coefficient therefore stops describing reality well above the yeast's minimum, and an earlier version of this model that set the floor at 8.0°C sat exactly on that singularity and returned short, finite times there, which is the opposite of the truth. The cost of the honest floor is worth stating plainly rather than hiding: this site's own cold band midpoint is 16.5°C, only 0.5°C above the floor, so a genuinely cold kitchen sits at the very edge of what this model can describe, and any temperature below 16°C is clamped to 16°C rather than answered. The ceiling is the optimum growth temperature the same table gives for L. sanfranciscensis LTH2581; it is not the warmest optimum in that table, since LTH1729 peaks at 33°C, so 32°C is one degree conservative of the table's warmest figure.

Tap for the source and reasoning

4-7 hours at 21°C overlaps both King Arthur figures without matching either. Their 4-6 hours is quoted at a warmer 78°F (26°C); their 6-8 hours is quoted at unspecified room temperature. Our range starts at the floor of the first, runs into the second, and stops an hour short of the 8-hour ceiling both pages reach. Feeding ratio moves this far more than temperature does: in the same trial a 1:1:1 feed peaked within 4 hours while 1:4:4 took 12, all at one temperature. This constant therefore carries real uncertainty that the temperature model cannot remove, and a baker watching their starter will beat the clock.

Tap for the source and reasoning

This value is faster than both cited sources and readers should know it. Interpolating Weekend Bakery's table to 21°C gives 5.5-7.25 hours, so our 4-5 hours does not overlap their range at all: it is quicker than anything they predict, not merely at their fast end. The Perfect Loaf's 2-5 hours is stated for a warmer 23-24°C dough, so at 21°C the same source implies slower than 5 hours. Differing inoculation does not explain the gap. Weekend Bakery state their table assumes "a healthy, active starter at around 20% inoculation", which is the proportion this site's calculators use throughout; they also assume 70-78% hydration and a final dough temperature close to ambient, which is what this model assumes too. Matched on every variable the source names, our figure is still materially the faster one, and we do not have an explanation for that which the sources support. The 4-5 hour window is carried over from the site's earlier hand-tuned timing tables; it is retained rather than quietly moved to a number we could not justify either, and it is labelled a deviation from the sources rather than dressed up as agreement with them. Judge the dough, not the clock.

Tap for the source and reasoning

1.5-3 hours sits inside the 1-4 hour room-temperature range this source gives, and its 3-hour ceiling matches the longest room-temperature proof the author reports using. The 1.5-hour floor is our own conservatism, not the source's: the source puts its floor at 1 hour and explicitly at room temperature, and reports 1 hour as its author's own shortest room-temperature proof. The separate warm case, 80°F/27°C, is where the source gives 1-2 hours. Raising the floor to 1.5 hours narrows the window for planning; a baker whose dough is ready sooner should trust the dough.

Tap for the source and reasoning

The 30-minute floor is supported: it clears King Arthur's 20-minute minimum and sits at the top of The Perfect Loaf's conservative 15-30 minute starting point. The 90-minute ceiling is not. King Arthur stop at 60 minutes, and The Perfect Loaf's everyday advice is 15, 30, 45 or 60 minutes, so our ceiling runs half an hour past both. The Perfect Loaf do go longer, but as a recommendation rather than a warning: they suggest "2 hours or more" for doughs with a high percentage of aged whole wheat, and say that autolysing overnight is "just fine" with some doughs, reporting good results. Their caution that too far is hard to reverse is attached to overnight or many-hour rests and names no threshold, so no source fixes a ceiling here at all. 90 minutes is a site choice, made to leave room for whole-grain blends, and it is above the cited range rather than a subset of it. Held fixed across temperature because autolyse is enzymatic rather than microbial, and because neither source varies its recommendation by kitchen temperature.

Tap for the source and reasoning

No source was found that puts a duration on mixing all ingredients in one go. Recipes describe the end state instead, for example King Arthur's "kneading to form a smooth dough". 10-15 minutes is carried over from the site's previous timing tables as a practical estimate and is flagged unsourced rather than given a citation that would not support it. Mixing is a mechanical task, so it does not vary with kitchen temperature.

Tap for the source and reasoning

No source was found supporting this range. The nearest figure located was King Arthur's Rustic Sourdough recipe, which specifies a 15-minute bench rest; that supports a bench rest existing but not the 20-45 minute combined shaping-plus-rest window used here, so it is deliberately not cited in support. Carried over from the site's previous timing tables and flagged unsourced. A human task, so independent of kitchen temperature.

Tap for the source and reasoning

Brackets the 40-45 minutes on a stone and 50 minutes in a Dutch oven that King Arthur give for a standard boule at 450°F. The 55-minute upper bound extends a little past the source to allow for larger loaves and is not itself stated by it. Governed by oven temperature, not kitchen temperature: the previous tables varied this across temperature bands, which was incorrect.

Tap for the source and reasoning

Hamelman names 75-78°F (about 24-26°C) as the temperature zone that works best, particularly for wheat-based breads. 25°C is the midpoint of that zone in whole degrees. Note the deliberate distinction from REFERENCE_TEMP_C (21°C): that constant anchors the timing model at a recognisable ambient kitchen temperature, while this one is the dough temperature worth aiming for, which Hamelman puts several degrees warmer than typical ambient. The water calculation exists exactly to bridge that gap.

Tap for the source and reasoning

The friction factor in the DDT method accounts for heat added by mechanical mixing, and Hamelman quantifies it for machine mixing. No source located quantifies a friction factor for hand mixing; the value of zero is a site choice, made because a few minutes of hand mixing adds heat below the precision of the rest of this calculation, and because a zero friction factor errs toward slightly warmer water, which a baker can feel and correct, rather than silently overshooting dough temperature. Bakers using a stand mixer will run a degree or two warm.

Tap for the source and reasoning

In a cold kitchen the DDT equation can ask for very hot water: at 16°C room and flour it returns 43°C. Gänzle et al. give Candida milleri, the yeast whose gas raises the dough, a maximum growth temperature of 35.9 ± 0.3°C, and L. sanfranciscensis 41°C. Rather than hand the starter water above the yeast's ceiling, the recommendation is capped at 35°C, just under the lowest Tmax in the table, and the plan says so when the cap bites. The specific margin is a site choice: mixing briefly dilutes the water's heat into cooler flour, so a degree or two above would probably be harmless, but "probably harmless" is not a claim the citation supports and the cost of slightly-too-cool water is only a slower ferment.

Tap for the source and reasoning

No published constant maps starter vigor to bulk fermentation time, so these factors are a rule of thumb and are labelled as one wherever they appear. The direction is well supported — Weekend Bakery note that a stronger inoculation (25-30%) speeds bulk fermentation while a weaker one (8-12%) slows it, and a starter used past its peak contributes less active culture in exactly the same way — but the magnitudes are ours. They are kept deliberately modest, at -15% for a starter that doubles within about 4 hours and +20% for one that takes 12 hours or barely rises, so that this heuristic can shade but never overwhelm the cited temperature model, which remains the dominant term. A baker with a genuinely sluggish starter should also read the starter troubleshooting pages: the better fix is reviving the starter, not planning around it.