The model: the sourdough clock

The most frequent question in bread making is not about grams: it is about the clock. «How long do I leave it?» This calculator turns the four numbers that govern fermentation — the kitchen temperature, the starter share, the growth target and the fridge temperature — into an hourly plan: the proofing hours at room temperature, the total minutes, the speed versus the base and the equivalent hours if the dough spends the night in the cold.

It is a declared planner, not an oracle: the base is the classic convention — four hours at 24 degrees with starter at 20 percent — and the factors are declared one by one. The real dough is judged with the eyes; the planner tells you when to start looking.

The four knobs: kitchen, inoculation, target and fridge

The room temperature has five values in steps of 4 degrees: 16 the winter kitchen, 24 the mid season, 32 the pushed summer. The starter share goes from 10 to 40 percent of the flour: from the slow inoculation to the decisive push. The growth target has three finish lines: 50 the prudent, 75 the classic, 100 the full doubling. The fridge temperature goes from 2 to 8 degrees — and touches a single row of the result, as we will see.

The temperature scale: four degrees that change the day

Starter at 20 percent, growth at 75; only the kitchen temperature changes:

Every four degrees the time is multiplied by two thirds: from the winter 16 to the summer 32 the same recipe goes from nine hours to under two — a factor of five without touching a gram. The middle row is the model's calibration: at 24 degrees the speed marks an exact 1.00, the yardstick every other row is measured against. And it is the lesson beginners learn in July: the winter recipe and the summer recipe are two different recipes — even when they are the same one.

The relative speed: the number that travels across seasons

The third number is the most portable: the speed versus the base, dimensionless. It is 1.00 in the reference kitchen and scales with everything else: 0.44 in the winter kitchen — less than half pace — 2.25 in the pushed summer. It is the number to remember when copying a recipe: if the author worked at speed 1 and your kitchen runs at 1.5, every one of their times must be divided by your pace — their four hours are your two hours forty. The model's default centres the base by construction: the factory recipe IS the yardstick.

The fridge: the input that touches a single row

The fourth input has a property unique in the model: the fridge temperature moves neither the room hours, nor the minutes, nor the speed — it touches only the last row, the hours in the cold. It is the most selective immobility in the catalogue: three results out of four are blind to the fridge, because the cold is a world apart — a declared decelerator, the multiplier that turns the base's 4 hours into the 20 of the night in the fridge. Whoever plans Saturday's pizza works exactly on that row.

The four readings: from the flash to the night

The verdict classifies the plan on the room clock. Under two and a half hours it is the flash fermentation: the dough does not wait, the timer commands. Between two and a half and five it is the daytime rhythm: it starts after breakfast, arrives before dinner — the window where one learns. Between five and nine it is the half day: the rhythm of planners and cool kitchens. From nine up it is the long proof: the evening dough for the morning oven, the territory of deep flavours.

The nine-hour border: the strict guard

The border between the half day and the long proof has its exact row: the winter kitchen at 16 degrees with the factory recipe produces precisely 9.0 hours. The model uses the strict guard: the border belongs to the upper band, and the exact 9.0 already reads «long proof». It is the prudent choice: on the border, the count prepares you for the night — better a long-proof plan than a dawn alarm for a dough that is not ready.

The double pace: when the timer becomes the main tool

Above the clock readings, the model marks a threshold on the speed: twice the base. From there up the good window is measured in minutes: half an hour of distraction separates the perfect dome from the overproof. The threshold can be touched with precision: starter at 40 percent in the reference kitchen — speed exactly 2.00, two hours sharp. It is the legitimate territory of fast summer fermentations, but the verdict declares it without discounts: at double pace, the timer is no whim.

The limits of the model: what the clock does not see

The perimeter is declared: this is a planner with explicit conventions — base 4 hours at 24 degrees, time inverse to the starter share, linear in the target, factor two thirds every four degrees, fridge as a multiplier. It does not see the starter's strength — a lazy starter shifts everything — nor the flour, nor the hydration, nor the salt that brakes. The numbers that come out are the starting plan: the dough is judged with the eyes — the dome, the bubbles, the mark on the container — and the planner tells you when to start watching it.

The starter scale: the rhythm knob

Reference kitchen at 24 degrees, growth at 75; only the amount of starter changes:

The proportion is declared and clean: half the starter, double the time — the 10 percent asks for eight hours, the 40 asks for two sharp at an exact speed of 2.00, the double-pace threshold touched to the hundredth. And it is the knob that designs the day: the finishing time is not chased, it is chosen — you want the oven at six starting at noon? The table says which inoculation makes it true.

The fridge scale: four degrees of patience

The factory recipe held still — four hours at room temperature; only the cold that receives it changes:

The room-hours column is a flat line — the fridge does not touch it, by construction — while the cold column slides from 22 to 16 hours: six hours of difference between the bottom shelf and the crowded summer fridge. It is the single-row immobility turned into a table, and its practical use is the evening plan: dough at eight, fridge at half past, oven at the hour YOUR shelf decides — a fridge thermometer costs little and is worth a loaf.

The recipe conversion: dividing by your own pace

The relative speed turns the calculator into a translator. The recipe says «four hours of bulk» but does not say at what speed the author's kitchen lived: assume it at the base — nearly all modern recipes are — and divide by your pace. Kitchen at speed 1.50: their four hours become two forty. Winter kitchen at 0.44: they become nine. The rule holds for every time in the recipe — folds, bulk, final proof — because fermentation scales all together: one single number converts the whole day.

The Saturday pizza plan: the fridge row at work

The cold row's best-loved use case is the weekend. Friday evening, 8 pm: dough with starter at 20. Half an hour of rest, then the container goes to the home fridge: the row says 20 hours — which lands at 4:30 pm on Saturday, just in time for dividing, a two-hour final proof at room temperature and the oven at 7. No night alarms, no rush: the cold has worked for you all night and half the afternoon. Long cold maturation is not an experts' technique: it is a civilised schedule — and the fridge row is its train timetable.

The target scale: three finish lines, three breads

The last factor is linear and honest: half the target, little more than half the time. The 50 percent growth — two hours forty at the base — is the prudent choice of weak flours and of doughs headed for the fridge anyway. The 75 — the base's four hours — is the modern finish line: full structure without risk. The 100 — five hours twenty — is the full doubling of the rustic loaves of old, to be granted only with flours that hold. The workshop rule stays sovereign: in doubt, the shorter target — the final proof always completes, the collapse never forgives.

The extremes of the grid: from 36 minutes to a whole day

The model's minimum is fermentation at a gallop: pushed summer at 32 degrees, starter at 40, prudent target and a warm fridge — 36 minutes, a proof watched stopwatch in hand, which no baker would recommend: it exists in the grid because it exists in August kitchens. The maximum is the contemplative opposite: winter kitchen, minimal inoculation, full doubling — exactly 24 hours, a whole day of room fermentation, the territory where sourdough gives its aromatic best. Between the two extremes runs a factor of forty: no other number in bread making moves this much — and that is why the clock is calculated, not guessed.

Frequently asked questions

How long should a sourdough dough proof?

With the classic recipe — starter at 20 percent, kitchen at 24 degrees, 75 percent growth — about four hours of bulk. But the number scales hard: the same recipe at 16 degrees asks for nine hours, at 32 under two. Temperature is the clock's most powerful knob.

How do I know the dough is ready, beyond the clock?

With the eyes and a graduated container: volume grown by the chosen target, a domed surface with bubbles showing through, and the fingertip test — the dent that springs back slowly. The planner says when to start looking; the dough says when it is done.

How much difference does kitchen temperature make?

A factor of two thirds every four degrees, by the model's declared convention: from 16 to 32 degrees the time divides by five. It is why the January recipe does not work in July — and the first number to update when the season changes.

How much starter goes into the dough?

The classic share is 15-25 percent of the flour. The model treats it as a rhythm knob: time inversely proportional — doubling the starter halves the wait. Less inoculation, more hours and more aroma; more inoculation, fewer hours and a narrower window.

What does the speed versus the base mean?

It is the pace of your fermentation against the reference kitchen (24 degrees, starter 20, growth 75): speed 1.00 is the base, 2.00 is double pace, 0.50 is half. It converts other people's recipe times: divide their times by your speed.

Why does the fridge not change the room hours?

Because they are two alternative roads, not a sum: either you leave the dough out for the indicated hours, or you put it in the cold for the fridge-row hours. The fridge touches only that row — it is the declared decelerator, not a corrector of the others.

How long does proofing last in the refrigerator?

The model uses a declared multiplier: at 4 degrees, the room time times five — the base's four hours become twenty, the classic night plus morning. At 2 degrees it stretches, at 8 it shortens: it is the knob of long maturation.

What is cold retarding and why do it?

It is fermentation slowed by the cold: enzymes keep working on starches and proteins while the yeasts nearly stop. The result is more aroma, better digestibility and a civilised schedule: the evening dough for the morning oven, with no night alarms.

Which growth target should I choose?

The 75 percent is the classic of the modern bulk: enough structure without risking collapse. The 50 is prudent — useful with weak flours or before a long night in the fridge — the 100 is the full doubling of rustic loaves. In doubt, stop earlier: the final proof completes the work.

What happens if the proof overshoots?

Overproofed dough loses its network: it deflates at the touch, smells sharply sour and does not spring in the oven. At double pace, thirty minutes of delay are enough. The remedies: fridge as soon as the target is reached, or — damage done — a reknead and a second life as focaccia.

Does the model work for baker's yeast too?

The relative proportions yes — temperature scales the same way — but the base no: baker's yeast is much faster and is dosed in grams, not as a starter percentage. This planner is tuned for sourdough; for yeast pizza the site has its dedicated calculator.

Why do temperatures go in steps of 4 degrees?

Because it is the model's honest resolution: the two-thirds factor is tuned on that step, and pretending single-degree precision would claim an accuracy real fermentation does not have — a home starter varies more than that from day to day. The planner gives the route; the real kitchen does the rest.

Updated July 2026