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Sourdough starter is not rising

After feeding, the culture sits flat: no doming, few or no bubbles through the side of the jar, and no measurable rise against the level it was fed at.

Usually established at: fermenting

Narrow it down

Answer what you can. Anything you skip simply leaves its causes in play — there is no requirement to answer everything, and no answer is treated as more authoritative than what you actually saw.

How warm is the spot the jar has been sitting in?
Before this feed, how long had it gone without one?
Has it come out of the fridge recently?
What did the water feel like when you fed it?
How have you been watching it?

All 5 possible causes are shown below. Answer a question above to start ruling them out.

Every possible cause

The complete model, whatever you answered above. Each cause states the mechanism — what physically happens — because a cause without a mechanism is folklore with a confident tone.

The kitchen is too cold for the culture

Very common

Fermentation rate depends strongly on temperature, and temperature is one of the few factors shown to affect which organisms are active at all. A culture that doubled in five hours in a warm kitchen may take twelve or more in a cold one, which reads as failure to a baker checking on the same schedule as before. Nothing is wrong with the culture.

The variable underneath

  • Dough temperature

    How to tell after the fact: A loaf that over-proved in less time than the recipe stated, in a warm kitchen, indicates dough that started warm.

What to change

  • Move it somewhere warmer, and wait longer

    Move the jar somewhere consistently warmer and give it longer before judging it. Mark the jar at the level of the fresh mixture so you are comparing against a line rather than a memory, and check periodically rather than once.

    Applies where the culture is being kept in a cold kitchen. It will not help a culture damaged by hot water, which is a different problem with a different fix.

    Trade-off: Warmer maintenance shifts the acid balance and means feeding more often. A cool, slow culture is not worse — it is on a different schedule.

It has gone too long between feeds

Very common

A culture consumes the sugars its enzymes release from the flour and excretes acid as it does so. Left unfed, it runs out of the first and accumulates the second, and the falling pH eventually suppresses even the organisms that produced it. The signs — a dark liquid layer, a sharp solvent smell, no visible gas — read as death and are almost always hunger.

The variable underneath

  • Refreshment ratio

    How to tell after the fact: A loaf that is markedly more sour than intended, from a culture that peaked quickly, points to too much old culture carried forward. A sluggish culture that never quite doubles points the other way — too little carried forward for the quantity of fresh flour, so the population is still climbing when the baker gives up on it.

What to change

  • Refresh it more often, and give it more to eat

    Discard most of the culture and refresh what remains with fresh flour and water, then repeat over the next day or two rather than judging it on a single feed. Carrying less old culture forward dilutes the accumulated acid, which is what is suppressing the population.

    Applies to a hungry, over-acidified or long-dormant culture — which covers the great majority of starters their owners believe to be dead. It does not apply where mould is present.

    Trade-off: You discard a good deal of material over those refreshments.

It is still dormant after refrigeration

Very common

Refrigeration slows the culture rather than stopping it, and the population that emerges is smaller, colder and more acidic than one kept at room temperature. It recovers, but over refreshments rather than immediately — so the first feed after the fridge routinely produces very little, and a baker who concludes from that single feed that the culture is dead discards a working one.

What to change

  • Judge it on the third refreshment, not the first

    After refrigeration, refresh the culture and let it come back over two or three cycles at room temperature before deciding whether it is working. The first feed after the fridge routinely produces very little and tells you almost nothing.

    Applies to any culture taken out of cold storage. The single most common reason a working starter gets thrown away.

    Trade-off: It costs a day or two before you can bake.

The water was hot enough to damage it

Occasional

The organisms in a culture are killed by sustained heat well below boiling. Water that feels hot rather than warm to the hand is enough to damage the population significantly when poured directly onto it. Unlike the other causes here, this one does real and sometimes irreversible harm — which is why it is worth ruling out first.

What to change

  • Use water that feels comfortably warm, never hot

    Use water that feels neutral to slightly warm against the inside of your wrist. If it feels hot, it is too hot. Where a culture has already been scalded, refresh it repeatedly from whatever survived and be prepared for it not to recover.

    Applies where hot water was poured onto the culture. Unlike the other causes here, this one can genuinely kill a starter.

    Trade-off: None.

It rose and fell before you looked

Common

A culture rises to a peak and then recedes as its gas escapes and its structure weakens. A warm kitchen, a generous carry-over of old culture or a very active starter can bring that peak forward by hours. A baker checking the next morning sees a flat, liquid-topped jar and concludes nothing happened, when in fact everything happened and finished.

The variable underneath

  • Refreshment ratio

    How to tell after the fact: A loaf that is markedly more sour than intended, from a culture that peaked quickly, points to too much old culture carried forward. A sluggish culture that never quite doubles points the other way — too little carried forward for the quantity of fresh flour, so the population is still climbing when the baker gives up on it.

What to change

  • Mark the jar so you can see a rise you missed

    Put an elastic band or a mark at the level of the culture immediately after feeding, and check it more than once. A culture that peaked and receded leaves evidence — a dried tidemark above the current level, and a domed-then-collapsed surface.

    Applies whenever the culture is only being observed once, many hours after feeding. Particularly likely in a warm kitchen or with a generous carry-over.

    Trade-off: None.

Preventing it next time

  • Mark the jar at the feed level so a rise you did not witness still leaves evidence.
  • Feed on a schedule that suits the temperature you actually keep it at, not the one a recipe assumed.
  • Use water that feels neutral against the wrist — this is the only item here that does lasting damage.
  • After refrigeration, judge the culture on its third refreshment rather than its first.

Most starters believed dead are hungry

A dark liquid layer on top, a smell like nail varnish and no visible activity are the signature of a culture that has run out of food and accumulated acid — not of one that has died. Two or three refreshments at room temperature, carrying only a small proportion forward each time, will revive the great majority.

The honest exception is heat. Water hot enough to feel hot will damage the population, and that damage is not always recoverable. It is the one item on this page worth ruling out first, because it is the only one where the answer might genuinely be to start again.

What the timings in recipes are not telling you

Published feeding schedules assume a temperature they rarely state. Because fermentation rate depends heavily on temperature, the same instruction produces a culture that peaks in five hours in one kitchen and fourteen in another. A schedule that worked in August and fails in January has not stopped working — the kitchen has changed.

Related

Possible causes

  • The kitchen is too cold for the culture

    Far and away the most common answer, and the one that requires no intervention beyond patience.

  • It has gone too long between feeds

    The state most often mistaken for death: exhausted substrate and accumulated acid suppressing the population.

  • It is still dormant after refrigeration

    A cold culture recovers over refreshments rather than immediately, which is why the first feed after the fridge tells you nothing.

  • The water was hot enough to damage it

    The only cause here that does lasting damage, so it is worth ruling out before the others.

  • It rose and fell before you looked

    The culture did everything it was supposed to, several hours before anybody looked.

If none of this matches what you saw, the model has a gap. Tell us — that is how this section gets better.

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