Part of: Fermentation School
Sourdough starters are resilient. Most “problems” are normal variations or easy fixes.
This guide helps you diagnose what’s wrong and what to do about it—without panic.
Quick Diagnosis Chart
| Symptom | Likely Cause | Fix |
|---|---|---|
| Not rising | Too cold, underfed, or young | Warm up, feed more often, wait |
| Rising then collapsing quickly | Over-fermented | Feed more frequently |
| Extremely sour smell | Over-fermented or hungry | Feed more often |
| No bubbles | Too cold or inactive | Warm up, feed regularly |
| Liquid on top (hooch) | Hungry | Pour off or stir in, then feed |
| Pink/orange color | Mold | Discard and start over |
| Smells like nail polish | Over-fermented | Feed more frequently |
| Dense, not spongy | Underfed or too cold | Feed regularly, warm up |
| Slow to rise | Cool temperature or weak culture | Warm up, feed regularly |
Problem: Not Rising
Symptoms
- Starter sits flat after feeding
- No visible increase in volume
- Few or no bubbles
Possible Causes
1. Temperature Too Cold
Yeast is most active at 70-85°F (21-29°C). Below 65°F (18°C), it slows dramatically.
Fix: Move your starter to a warmer spot:
- Top of the refrigerator
- Near a warm appliance
- In the oven with just the light on
- In a cooler with a jar of warm water
2. Not Enough Food
If you’re keeping too much starter and not adding enough fresh flour, the yeast runs out of food before it can build momentum.
Fix: Increase your feeding ratio. Instead of 1:1:1 (starter:flour:water), try 1:2:2 or even 1:3:3.
3. Starter Is Too Young
New starters (less than 2 weeks old) are still developing their yeast population. They rise slowly or inconsistently.
Fix: Be patient. Keep feeding daily. It will strengthen.
4. Weak Culture
If your starter has been neglected or stored cold for a long time, the yeast population may be low.
Fix: Feed small amounts frequently. Keep 10g starter, feed with 20g flour + 20g water every 12 hours for 2-3 days.
Problem: Rises Then Collapses Quickly
Symptoms
- Starter doubles or triples rapidly (within 2-4 hours)
- Then collapses back down
- May have a “dome” that sinks in the middle
Cause: Over-Fermentation
Your starter is healthy and vigorous—but it’s running through its food too fast.
Fix: Feed more frequently, or increase the amount of flour.
Options:
- Feed twice a day instead of once
- Use a higher ratio: 1:3:3 (starter:flour:water)
- Refrigerate between feeds if you can’t keep up
This is actually a good “problem”—it means your starter is strong.
Problem: Extremely Sour Smell
Symptoms
- Very sharp, acidic smell
- Almost vinegary
- May make your eyes water
Cause: Over-Fermentation
The bacteria that produce acid have outpaced the yeast. This happens when the starter sits too long between feeds.
Fix: Feed more frequently. The sourness will mellow.
Note: Some bakers prefer a more sour starter. If you like the flavor, this isn’t a problem—just know that very acidic dough can weaken gluten structure.
Problem: Liquid on Top (Hooch)
Symptoms
- Clear or grayish liquid floating on top
- May smell like alcohol or nail polish
Cause: Hunger
Your starter has consumed all available food and started to break down its own structure. The liquid is alcohol produced by fermentation.
Fix:
- Pour off the liquid (for milder flavor) or stir it in (for more sour)
- Feed immediately
- Feed more frequently going forward
Prevention: Feed before hooch forms. If you see hooch regularly, your starter is telling you it needs more frequent feeds.
Problem: Smells Like Nail Polish or Acetone
Symptoms
- Sharp, chemical smell
- Reminds you of nail polish remover
Cause: Over-Fermentation
This is a stage of severe hunger. The starter has produced so much acid that it’s creating acetone-like compounds.
Fix:
- Pour off any hooch
- Take a small amount (10g) and feed with fresh flour and water
- Feed again in 12 hours
- Repeat until the smell normalizes
This usually takes 2-3 feedings.
Problem: Dense, Not Spongy
Symptoms
- Starter looks thick and paste-like
- No air bubbles visible
- Doesn’t increase in volume
Possible Causes
1. Underfed
The yeast population has declined from lack of food.
Fix: Feed regularly for 3-5 days. The texture should improve.
2. Too Cold
Yeast isn’t active enough to produce gas.
Fix: Move to a warmer location.
3. Too Much Flour
If your starter is very thick (like dough rather than batter), gas bubbles can’t form properly.
Fix: Add more water. The consistency should be like thick pancake batter.
Problem: Pink, Orange, or Red Color
Symptoms
- Pink, orange, or reddish streaks or patches
- May be fuzzy or slimy
Cause: Mold
This is the one problem that means you must discard and start over.
Fix: Unfortunately, there’s no saving a moldy starter. The mold has sent threads throughout the culture, even if you can’t see them.
Prevention:
- Use clean utensils
- Keep the jar rim clean
- Don’t let debris fall into the starter
- Keep covered (but not airtight)
Problem: Slow to Rise
Symptoms
- Takes 8-12+ hours to double
- Seems sluggish compared to descriptions you’ve read
Possible Causes
1. Cool Temperature
Most “ideal” timelines assume 75-80°F (24-27°C). At 68°F (20°C), everything slows down.
Fix: Warm up your starter, or adjust your expectations. Slow isn’t bad—it’s just slow.
2. Young Starter
Starters under 2 weeks old are still building their yeast population.
Fix: Keep feeding. It will speed up.
3. Weak Culture
If your starter has been neglected, it may need time to rebuild.
Fix: Feed small amounts frequently (every 12 hours) for several days.
Problem: Unpleasant or “Off” Smell
Symptoms
- Smells rotten, putrid, or just wrong
- Not sour—bad
Cause: Contamination or Dead Culture
This is rare but happens.
Fix:
- If it smells rotten (not just sour), discard
- If it smells extremely sour but not rotten, try reviving with 2-3 days of frequent feeds
- If the smell doesn’t improve, start over
Problem: No Bubbles at All
Symptoms
- Completely flat surface
- No visible activity
- Looks like flour and water paste
Possible Causes
1. Brand New Starter
In the first 2-3 days of creating a starter, there may be no visible activity. This is normal.
Fix: Keep going. Feed daily. Bubbles will come.
2. Temperature Too Cold
Fix: Move to a warmer spot.
3. Dead Culture
If your starter was frozen, overheated (above 120°F/49°C), or neglected for weeks, the culture may have died.
Fix: Try reviving with frequent feeds. If no activity after 3 days, start over.
The Revival Protocol
If your starter is struggling but not moldy, try this:
- Take 10g of starter (even if it looks sad)
- Feed with 20g flour + 20g water
- Wait 12 hours at room temperature (70-75°F / 21-24°C)
- Repeat steps 1-3 for 3-5 days
- Assess: If bubbles and rise appear, it’s reviving
If after 5 days there’s no improvement, start fresh.
When to Start Over
Sometimes it’s not worth fighting. Start a new starter if:
- Visible mold (pink, orange, black, fuzzy)
- Foul, rotten smell that doesn’t improve with feeding
- No activity after 5+ days of revival attempts
- You just want a clean slate
A new starter takes 5-7 days. Sometimes that’s faster than reviving an old one.
Prevention: The Best Troubleshooting
Most problems come from:
- Inconsistent feeding — Establish a routine
- Wrong temperature — Find a warm, stable spot
- Not discarding enough — Keep the ratio reasonable
If you feed your starter regularly and keep it at a comfortable temperature, most of these problems never happen.
Next Steps
- Sourdough Starter Maintenance — A simple system for keeping your starter healthy
- Sourdough Starter Recipe — Create a new starter from scratch
- Fermentation Safety — General fermentation safety guidelines
