Why Isn't My Sourdough Starter Rising? A Diagnostic Checklist
A starter that won’t rise feels like a failure, but it almost never is. A sourdough starter is a stable microbial community — wild yeast plus lactic acid bacteria (LAB) — living in a flour-and-water slurry. When it doesn’t rise, that community is almost always still alive; one variable has simply slowed it down or shifted its timing. Truly dead starters are rare. Your job is to find the one variable that’s off.
This is a triage tree: work through the causes in order, most common first, and stop when one fits. For the vocabulary — starter, hooch, float test, peak, LAB, wild yeast, feeding ratio — keep the Sourdough Glossary open in another tab.
1. It’s too cold (the number one cause)
Symptom: Your starter looks flat, barely moves over 12 hours, and smells mild rather than tangy. It was livelier in summer, or livelier on the counter than in the cupboard.
The biology: Wild yeast and LAB are temperature-driven engines. Below about 21°C (70°F) their metabolism slows sharply; carbon dioxide is produced too slowly to lift the dough, so you never see a dome. The rule of thumb is the Q10 effect: across the relevant range, fermentation rate roughly doubles to triples for every 10°C of warming, and falls by the same factor on cooling — the effect is steeper at cooler temperatures. A starter that peaks in 6 hours at 26°C might need 18+ hours at 16°C — check at hour 8 and it looks “dead.”
The fix: Give it warmth, around 24–27°C (75–80°F). Options: an oven with only the interior light on, the top of the fridge, near (not on) a warm appliance, or a dedicated proofing box. A few degrees is the difference between “nothing’s happening” and a reliable, predictable rise.
2. It’s a brand-new starter, mid-establishment
Symptom: Days 3–5 of a from-scratch starter. It rose impressively early, then went quiet and “died.” Now nothing happens no matter how you feed it.
The biology: This is the single most misread phase in sourdough. A new starter is a succession of microbial communities, not one. In the first few days, non-yeast bacteria such as Leuconostoc bloom and produce gas — that’s the deceptive early rise. They acidify the environment, then crash. What follows is a quiet lull, sometimes a couple of flat days, while the acid-tolerant wild yeast and LAB that define a mature sourdough culture slowly establish dominance. This stable community typically takes one to two weeks (sometimes longer) to take hold.
The fix: Patience, not panic. Keep feeding on a consistent schedule and keep it warm (see cause 1). Don’t toss it during the lull — that lull is the culture reorganizing itself. The “it rose then died” story is almost always a healthy starter being judged three days too early.
3. Feeding: too little, too late, or too often
Symptom (underfed-per-feed): Your starter shoots up and collapses fast, and by the time you look it’s already fallen — a thin liquid (hooch) on top, a sharp acetone or vinegary smell.
Symptom (neglected/hungry): A starter left for days or weeks: sluggish, sour, slow to wake, hooch on top.
The biology: A vigorous starter is a hungry one. At a small feeding ratio like 1:1:1 (equal parts starter, flour, water), you add very little fresh food relative to a dense, active population. They exhaust the sugars in a few hours, peak, and fall — so the rise happens and is over before you check. At the other extreme, a long-neglected starter has eaten everything, accumulated acid, and gone dormant. Hooch means hungry, not dead — pour it off or stir it in and feed.
The fix: Feed a larger ratio — 1:5:5 or more (one part starter to five parts each fresh flour and water). More fresh food lengthens the climb to peak and makes the rise easy to catch. Discard down to a small amount first so the ratio is real, and feed on a regular schedule (every 12–24 hours at room temperature). A neglected starter usually needs two or three consecutive feedings to come fully back.
4. The flour is working against you
Symptom: A weak, slow rise that doesn’t improve with warmth or feeding tweaks — often on a starter built entirely with white, highly refined, or old flour.
The biology: Flour is the fuel and the seed stock. Whole grain and rye flours carry more of everything the culture needs: more amylase and other enzymes to release sugars, more minerals, and a richer load of wild microbes on the bran. Bleached or very refined white flour is stripped of much of this, and old or stale flour has degraded enzyme activity. Either ferments weakly.
The fix: Add some whole wheat or rye — replacing even 20–30% of the white flour at feeding often visibly wakes a sluggish starter, and rye is the most reliable jump-start there is. Use fresh flour, and avoid bleached flour for building or maintaining a starter.
5. The water is chlorinated
Symptom: A consistently underperforming starter where temperature, feeding, and flour all look right — and your tap water is heavily treated.
The biology: Municipal disinfectants are designed to kill microbes and in high enough concentration can inhibit yours. The part widely gotten wrong: chlorine off-gasses if you leave water out overnight, but chloramine does not. Many utilities now use chloramine precisely because it’s stable, so the old “leave it on the counter” trick won’t help.
The fix: Use filtered water (a carbon filter removes both chlorine and chloramine), or bottled water. If your utility uses plain chlorine, leaving water out uncovered for several hours works. If you’re unsure, just filter — it covers both cases.
6. Hydration is hiding the rise
Symptom: Your starter is fermenting fine — bubbles, sour smell, clear activity — but it never shows a tall, obvious dome.
The biology: Consistency changes what you see and what the culture makes. A stiff, low-hydration starter has a tight gluten network that traps gas differently and rises less visibly — it’s working, but it won’t balloon the way a wetter one does. Hydration also shifts the acetic-to-lactic acid balance (stiffer favors sharper acetic acid, wetter favors milder lactic acid), which affects flavor more than height.
The fix: To read your starter reliably, standardize to roughly 100% hydration (equal weights of flour and water). At that consistency the rise-and-fall is unmistakable, which makes every other diagnosis on this list easier.
7. It’s active — you just keep missing the peak
Symptom: It “never rises,” yet there are bubbles in and on the surface and it smells alive. You feed it, leave for work or sleep, and it looks the same when you return.
The biology: Nothing is wrong. The starter rose to its peak and fell back while you weren’t watching — often in well under 12 hours once it’s warm and well-fed. A flat surface with internal bubbles is the fingerprint of a rise that already happened.
The fix: Mark the jar with a rubber band or tape at feeding height and watch for the dome — that’s peak, and that’s when it’s most active. The float test (a spoonful floating in water) is a rough gas check at best; it’s genuinely unreliable, especially for wet starters, so don’t treat a sinking blob as proof of death. The honest way to know your starter is to watch its height over a few hours — exactly the timing problem The Sourdough Companion is built to track for you.
Quick triage table
| Symptom | Likely cause | Fix |
|---|---|---|
| Flat, barely moves, mild smell | Too cold (cause 1) | Warm to 24–27°C |
| Rose around day 3, then “died” | New starter mid-establishment (cause 2) | Keep feeding; wait 1–2+ weeks |
| Peaks and falls fast; hooch; sharp smell | Underfed per feeding (cause 3) | Feed 1:5:5 or higher |
| Sluggish, very sour, dormant | Neglected/hungry (cause 3) | Discard down, feed 2–3× |
| Weak rise despite warmth + feeding | Refined or old flour (cause 4) | Add whole wheat/rye; fresh flour |
| Consistently weak, heavily treated tap water | Chlorine/chloramine (cause 5) | Filtered water |
| Bubbles and sour smell but no dome | Too stiff to read (cause 6) | Standardize to 100% hydration |
| Looks flat but bubbly inside | Missed the peak (cause 7) | Mark the jar; watch for the dome |
Is it actually dead?
Almost certainly not. A truly dead or unsafe starter announces itself: fuzzy mold (any color) or pink, orange, or red streaks, both of which mean discard and start over — no rescue. Otherwise, the warning signs people fear are usually benign: hooch is hunger, a vinegary or acetone smell is over-fermentation (feed more, sooner), and a stretch of flatness is dormancy, not death. When in doubt, give it warmth, a couple of generous feeds with some whole grain flour, and three days. If you want to build a fresh, predictable culture from scratch, see levain vs starter, and how to build one.
Most “dead” starters are just cold, hungry, or mis-timed. Diagnose one variable at a time, change it, and watch the jar — the rise you were waiting for was usually there all along, or one small adjustment away. Sourdough cultures are far more resilient than they look; correct the condition and the community comes back.