Sourdough Starter Troubleshooting

How to Use This Guide

Find your symptom below, read the diagnosis, and follow the fix. Sourdough starters are remarkably resilient — most problems are fixable with a feeding adjustment or a little patience. If you're just getting started, check out our Sourdough Starter Guide for the day-by-day process.

My Starter Isn't Rising

This is the most common sourdough frustration, especially in the first week. Here's what's going on and how to fix it.

It's too early (days 1–4)

Many starters show a burst of activity on days 2–3 from leuconostoc bacteria — early colonizers that produce lots of gas. Then activity dies down on days 4–5 while the real sourdough microorganisms (wild yeast and lactobacillus) establish themselves. This is completely normal. Most people panic during this lull, but the starter isn't dead — it's transitioning. Keep feeding daily.

It's too cold

Temperature has a huge effect on fermentation speed. Starters are happiest at 75–80°F (24–27°C). In a cold kitchen (below 68°F), everything slows dramatically — a starter that would double in 6 hours at 78°F might take 12+ hours at 65°F.

Warm spots to try:

• On top of the refrigerator (warm air rises)
• Inside the oven with just the light on (test the temperature first — some oven lights make it too hot)
• Near (not on) a radiator or heat vent
• On top of a cable box or other electronics that run warm

The flour is wrong

Heavily bleached all-purpose flour has fewer of the wild yeast and nutrients that starters need. Switch to unbleached all-purpose or bread flour. Adding 20–30% whole wheat or rye flour to your feedings gives extra nutrients and microorganisms that can kickstart a sluggish starter.

The water is chlorinated

Heavily chlorinated tap water can inhibit the microorganisms in your starter. Solutions:

• Let tap water sit uncovered for 24 hours — chlorine evaporates
• Use filtered water
• Note: chloramine (used in some municipal water) does NOT evaporate. If your city uses chloramine, use filtered water

You're discarding too much (or too little)

If you don't discard enough before feeding, the ratio of old starter to fresh flour is too high — the acids build up and the pH drops too low for the yeast to thrive. Aim to keep about 50g of starter and feed with 50g flour + 50g water (a 1:1:1 ratio). Some sluggish starters benefit from a higher feed ratio like 1:2:2 — keep 25g of starter and add 50g each of flour and water.

It Smells Like Acetone or Nail Polish Remover

This is acetic acid buildup — your starter is hungry. The bacteria have consumed all available sugars and are producing sharp, volatile acids. This is not dangerous, and the starter is not ruined.

The fix

• Feed immediately: discard all but 25g of starter, add 50g flour + 50g water
• Feed twice a day (every 12 hours) for 2–3 days until the smell mellows to a pleasant yogurty sourness
• Make sure your feeding ratio is generous enough — the starter needs plenty of fresh flour to eat
• If this happens regularly, your kitchen may be too warm (bacteria outpace the yeast at high temperatures)

There's Dark Liquid on Top (Hooch)

That dark, sometimes grayish liquid is called “hooch” — it's alcohol produced by the yeast when the starter runs out of food. It's not harmful, and it's a clear signal that your starter needs to be fed more often.

What to do

• Pour it off for a milder-flavored starter
• Stir it back in for a more sour, tangy flavor in your bread
• Then feed as usual

Preventing hooch

• Feed more frequently (every 12 hours if on the counter)
• Use a larger feed ratio (1:2:2 instead of 1:1:1)
• If you don't bake often, store it in the fridge and feed weekly

It Rose on Day 2 Then Went Flat

This is the infamous “false rise.” On days 2–3, leuconostoc bacteria (which are already present on the flour) produce a burst of gas. They're not the sourdough organisms you want — they're just the first to show up. Over the next few days, the environment becomes too acidic for them and they die off.

Meanwhile, the real sourdough culture (wild yeast + lactobacillus) is slowly establishing itself. This transition period on days 4–7 often looks like “nothing is happening.” It is. Keep feeding.

My Starter Has Mold

Real mold on a sourdough starter is uncommon but does happen, especially in the first few days before the culture becomes acidic enough to protect itself.

What mold looks like

• Fuzzy spots — usually pink, orange, green, black, or white with a furry texture
• Grows on the surface or sides of the jar above the starter level
• Distinctly different from the bubbles or dry flour residue on the jar walls

What to do

If the mold is just on the jar rim or above the starter line, you can try scooping out a small amount of starter from the center (avoiding the moldy area), putting it in a clean jar, and feeding. However, if the mold is growing on the starter itself, discard and start fresh.

Preventing mold

• Use a clean jar — switch to a fresh jar every few days during the first week
• Use a wide-mouth jar so air can circulate (mold thrives in stagnant, humid conditions)
• Cover loosely, not airtight
• Keep starter in a warm spot — warmth encourages faster acidification, which protects against mold

It Smells Rotten or Like Vomit

A truly foul, putrid smell (as opposed to strong/sour) usually means the wrong bacteria dominated the culture. This sometimes happens in the first few days when the pH hasn't dropped enough to select for the right microorganisms.

What to do

• Discard all but a tablespoon of starter
• Feed with a generous amount of flour: 1:5:5 ratio (1 part starter, 5 parts flour, 5 parts water)
• This dilutes the bad bacteria and gives the lactic acid bacteria a fresh start
• Feed twice daily for 2–3 days
• If the smell persists after 3 days of aggressive feeding, start over with fresh flour

My Starter Doubles but Bread Won't Rise

If your starter looks active but your bread isn't rising, the issue may not be the starter at all. Common causes:

• Timing. You're using the starter too early (before peak) or too late (after it's collapsed). Use it when it's doubled and domed — not when it's already fallen back down.
• The float test. Drop a spoonful of starter into water. If it floats, it has enough gas to leaven bread. If it sinks, feed it and wait for peak activity.
• Dough temperature. Cold dough rises slowly. Bulk fermentation should happen at 75–80°F for predictable results.
• Over-proofing. If you let the dough ferment too long, the gluten structure breaks down and the bread goes flat. Watch the dough, not the clock.

For a full walkthrough, see our Sourdough Bread guide.

I Forgot to Feed It (for Days, Weeks, or Months)

Sourdough starters are incredibly hardy. Here's how to revive one depending on how long it's been neglected:

Forgot for a few days (counter)

Pour off any hooch, discard all but a tablespoon, and feed normally. It should bounce back within 1–2 feedings.

Forgot for weeks (fridge)

Take it out, let it come to room temperature, pour off hooch, and discard all but a tablespoon. Feed with a 1:5:5 ratio. It may take 2–4 days of twice-daily feeding to fully revive, but starters that have been refrigerated for weeks almost always recover.

Forgot for months (fridge)

Still probably fine. Follow the same process as above, but expect it to take 4–7 days of consistent feeding. Even starters that look completely lifeless — gray, smelly, separated — often come back. People have revived starters after 6+ months of fridge neglect.

It's Separating — Liquid on Top, Thick on Bottom

This is a hydration issue, not a health issue. The starter is separating because the flour has absorbed the water unevenly, or because it's been sitting too long between feedings. Stir it back together, discard, and feed. If it keeps separating, try using a slightly thicker hydration (reduce water by 5–10g per feeding).

Quick Reference: What's Normal vs. What's Not

Normal (keep going):

• Bubbles of all sizes — tiny, large, foamy
• Sour, yogurty, or mildly vinegary smell
• Dark liquid on top (hooch) — just hungry
• Quiet days 4–5 after initial burst — the transition
• Slow activity in a cold kitchen — needs warmth
• Slightly beery or fruity smell — yeast activity
• Not doubling until day 7–14 — some starters are slow

Fix it (but don't toss it):

• Acetone/nail polish smell — feed more often
• Not rising at all after 10+ days — change flour, add warmth, check water
• Separating — stir, feed, adjust hydration
• Strong vinegar smell — too long between feedings

Start over if:

• Fuzzy, colored mold growing on the starter surface
• Persistent rotten/putrid smell that doesn't improve after 3 days of aggressive feeding
• Pink or orange streaks (can indicate harmful bacteria)