Sourdough starter not rising: how to find the real cause

Most of the time, a sourdough starter not rising is cold — not dead. Below 70°F, a healthy starter can take 12 hours or more to peak, long after you've stopped watching. Work the causes in order: temperature, flour, ratio, then everything else.

Temperature: the top reason for a sourdough starter not rising

Wild yeast in a starter is most active around 75–82°F (24–28°C). A 66°F kitchen won't kill anything, but it stretches the timeline well past the point where most bakers give up. Winter counters, tile, and anything against an exterior wall run several degrees below what the thermostat reads. Put a thermometer in the jar before you change anything else.

Starter temperature	Typical time to peak	What you see at the 6-hour mark
65°F / 18°C	12–24 hours	Barely domed, scattered bubbles
70°F / 21°C	8–12 hours	Climbing, maybe halfway
75°F / 24°C	6–8 hours	At or near peak
80°F / 27°C	4–6 hours	Peaked, starting to sink
85°F / 29°C	3–4 hours	Already fallen, thin, sharply sour

Those ranges assume a mature starter fed 1:1:1 by weight on unbleached all-purpose flour. Yours will land somewhere inside them.

Warm spots that work: an oven with only the light on (check it holds under about 85°F), the top of the refrigerator, or a cooler with a jar of hot water swapped twice a day. Warmer isn't automatically better — push the sourdough starter temperature much past 85–90°F and acid-producing bacteria outrun the yeast, leaving a thin, sour culture that rises less than it did at 78°F.

Your starter may be doubling — you're just missing the peak

A starter that peaks at four hours and has collapsed by the time you look at hour ten is indistinguishable from one that never rose. Both are flat. Both look wet. Both bubble only at the edge.

The tell is on the glass: a thin dried rim above the current surface marks how high the starter actually got. A sourdough starter not doubling on the schedule you expect is often doubling on a schedule you haven't measured.

So measure it. Put a rubber band at the feed line, check every two hours through one cycle, and write down when it stops climbing. That peak time is the number you feed and bake by, and it shifts with the season. If you're running more than one starter, or feeding at hours you won't remember, Sourdough Tracker is a sourdough baking companion app for iPhone.

And stop treating flotation as your only readiness check. A starter can be fully active and still sink, especially at high hydration — the float test confirms a yes far better than it diagnoses a no.

Flour is the second thing to change

White all-purpose flour is the thinnest diet you can put a starter on. Whole grain flours carry more minerals and enzyme activity, plus wild yeast and bacteria living on the bran, and they ferment noticeably faster. The cheapest upgrade is replacing 10–25% of each feed with whole rye. Rye is the reliable one; whole wheat works too, just less dramatically.

Two flour notes worth knowing:

• Bleached flour is worth avoiding in a starter. Unbleached is the safer default and costs about the same.
• A brand-new starter commonly surges on day two or three, then goes flat for several days. That first surge usually isn't the yeast you're trying to grow, and the quiet stretch after it is normal. Keep feeding on schedule.

Ratio, jar, and water

Ratio. Topping up a large jar with a spoonful of flour feeds a big, old, acidic culture almost nothing, and acidity by itself suppresses rise. Discard down to 20–50 g and feed 1:1:1 by weight. The opposite error exists too: a 1:5:5 feed in a cold kitchen dilutes an already-slow culture into invisibility. Match the feeding ratio to the temperature — bigger ratios for warm rooms, smaller for cold ones.

Jar. A wide jar spreads the same gas across more surface area, so a genuine doubling reads as a shrug. Use a straight-sided jar holding two to three times the volume of the starter, and mark the level.

Water. Cold tap water in a cold kitchen drops the jar several degrees right when it needs to climb. Water at about 85–90°F pulls it up instead.

Chlorine and stale flour come last

These two get repeated the most and cause the fewest problems. Municipal chlorine is generally too dilute to kill an established starter; plenty of bakers use tap water and never think about it. If your utility treats with chloramine instead, leaving water out overnight won't drive it off the way chlorine dissipates. Two feeds with bottled water is a cheap test — if nothing changes, water wasn't the problem.

Stale flour matters mostly for whole grain, which carries oil in the germ and eventually goes rancid. If the bag smells like old paint or crayons, that's your answer.

How to revive a sourdough starter in three days

This works for an ignored fridge starter and for a room-temperature one that's gone quiet.

1. Discard hard. Keep 20 g. Pour off any dark hooch first.
2. Feed 1:1:1 with a rye boost. 20 g starter, 20 g water at about 85°F, 20 g flour — make that flour 15 g unbleached white plus a spoonful (roughly 5 g) of whole rye.
3. Hold it at 78–80°F and repeat every 12 hours.
4. Read the signs, not the calendar. Day one is often silent. By day two you should see bubbles and some doming. By day three a recovering starter is doubling within 6–8 hours.

If day three brings movement but not a double, shift to 8-hour feeds for another day. Slow but steadily improving is a starter on its way back.

How long can sourdough starter go without feeding?

At room temperature, 12–24 hours is a normal gap and two days is pushing it; past that it's spent, acidic, and slow. In the refrigerator, a week or two is routine and a couple of months is survivable. Long-neglected fridge starters usually come back, but they need the three-day protocol above rather than a single feed. If you keep yours in the fridge, give it two or three room-temperature feeds before baking. Dark liquid on top, hooch, means hungry rather than dead.

When a starter really is dead

Very few are. The short list is fuzzy mold of any color, including raised white fuzz, and pink or orange streaks through the culture. Either one, throw it out and start over with a scrubbed jar. Everything else — acetone smell, gray hooch, sharp vinegar, a separated layer — is hunger, and feeding fixes it.

FAQ

Why is my sourdough starter bubbly but not rising?

Bubbles without lift usually mean the bacteria are running ahead of the yeast, which happens in a jar that's too warm, too acidic, or fed too little. Discard down to 20 g, feed 1:1:1, and hold it at 75–78°F. In a young starter, the flat stretch after the first few days is expected.

What is the best temperature for sourdough starter?

Roughly 75–80°F (24–27°C) for daily maintenance: fast enough to peak in 4–8 hours, not so warm that acidity takes over. Cooler is fine if you extend the timeline to match. The temperature you can hold steady beats the theoretically ideal one, because consistency is what makes peak time predictable.

My starter smells like nail polish remover. Is it ruined?

No. Acetone is the smell of a starter that has eaten everything available and is now producing alcohol and acid. Feed it, and if the smell returns quickly, feed it more often or at a larger ratio.

Should I throw out a starter that hasn't risen in a week?

Not unless it has fuzzy mold or pink streaks. A week of sourdough not rising is almost always temperature, thin flour, or a starved ratio. Run the three-day revival with rye at 78–80°F before giving up on it.