Sourdough Starter Smells Like Acetone or Nail Polish? Here’s Exactly What It Means (And How to Fix It Fast)

If your sourdough starter smells like acetone or nail polish remover, it’s usually hungry—not bad.
That sharp smell comes from excess acid when the starter runs out of food. In most cases, you can fix it within 24–48 hours by feeding a larger ratio and refreshing it more frequently.

If your starter smells like acetone, nail polish remover, paint thinner, or sharp vinegar, don’t panic. This is a common and fixable issue, not a sign that your starter is ruined.

Below is the exact diagnosis, the fastest fix, and how to tell when the smell is a real problem.

Why does sourdough starter smell like acetone or nail polish remover?

An acetone or nail-polish smell happens when your starter runs out of food.

Here’s what’s happening:

• Yeast and bacteria consume the sugars in flour
• When sugars run low, fermentation shifts
• Acids accumulate
• Sharp, solvent-like aromas are produced

Common reasons sourdough starter smells like acetone:

1. The starter is overdue for feeding
2. The environment is too warm and fermentation is too fast
3. The feeding ratio is too small
4. The starter sat too long in the fridge without refreshment
5. The starter is new and still stabilizing (days ~3–10)

An acetone smell in sourdough starter is a sign of starvation and acid buildup, not spoilage.

Is sourdough starter with an acetone smell safe to use?

In most cases, yes.

Normal and fixable (keep your starter)

• Smells sharp, vinegary, or like acetone
• Has hooch (gray or brown liquid)
• Bubbles or rises at some point
• No fuzzy growth or unusual colors

Not safe (discard immediately)

• Fuzzy mold (white, green, blue, or black)
• Pink or orange streaks or patches
• Putrid, rotting smell combined with visual changes

If you see mold or pink/orange discoloration, discard the starter and start fresh.

How do you fix a sourdough starter that smells like acetone?

The fix is simple: feed more, and feed sooner.

How to fix a sourdough starter that smells like acetone:

1. Discard all but 20g of starter
2. Feed with a 1:3:3 ratio (starter : water : flour)
3. Keep the starter at 72–78°F (22–26°C)
4. Feed again when the starter peaks, not by the clock
5. Repeat for 24–48 hours

Detailed “Acetone Reset” Method

Step 1: Reduce the starter

• Keep only 20g starter
• Discard the rest

Step 2: Feed at a higher ratio

• Add 60g water
• Add 60g flour
• (1:3:3 feeding ratio)

Step 3: Control temperature

• Ideal range: 72–78°F (22–26°C)
• Temperatures above 80°F (27°C+) speed acid production

Step 4: Feed at peak

• Feed when the starter domes, bubbles heavily, then just begins to flatten
• If it peaks in 6 hours, feed every 6–8 hours
• If it peaks in 10–12 hours, feed every 12 hours

What you should notice

• The acetone smell fades after 1–2 feedings
• Within 24–48 hours, the aroma becomes mildly tangy, yogurt-like, or lightly fruity

Why does sourdough starter smell like acetone in the fridge?

This is extremely common.

Refrigerated starters ferment slowly but still consume food. Over time, they become hungry and produce hooch and sharp aromas.

How to fix a refrigerated starter with an acetone smell

1. Pour off hooch (or stir it in if you prefer more sourness)
2. Take 10–20g starter
3. Feed 1:3:3 (or 1:5:5 if your kitchen is warm)
4. Keep at room temperature until it peaks
5. Feed once more, then refrigerate

If you bake weekly, refresh your starter at least once per week, even if it lives in the fridge.

Why bigger feedings fix the acetone smell

The acetone smell comes from too much acid and not enough food.

Larger feeding ratios:

• Dilute excess acids
• Add more fermentable sugars
• Restore balance between yeast and bacteria

This is why small feedings like 1:1:1 often don’t fix the problem.

What feeding ratio should you use?

Use 1:3:3 if:

• Your starter smells like acetone
• It peaks in under 8–10 hours
• Your kitchen is moderate in temperature

Use 1:5:5 if:

• Your kitchen is warm (78–84°F / 26–29°C)
• The starter peaks very quickly
• You want a longer fermentation window

Use 1:2:2 if:

• Your kitchen is cool
• Your starter is sluggish and needs strengthening

Should you stir in hooch or pour it off?

Both are safe.

• Pour off hooch to reduce acidity faster
• Stir it in if you want a more sour starter

If your goal is to eliminate a nail-polish smell quickly, pour it off.

New starter? Strong smells can still be normal

If your starter is under two weeks old, smell swings are common:

• Days 2–4: funky or cheesy
• Days 4–10: sharp or solvent-like
• Weeks 2–3: becomes more stable

Judge a young starter by rise and bubbling, not smell alone.

How to prevent acetone smell long-term

1. Feed based on peak, not the clock
2. Match feeding ratio to room temperature
3. Keep smaller starter amounts (20–50g)
4. Add a small portion of whole grain flour if desired

Simple flour blend:

• 80–90% bread or all-purpose flour
• 10–20% whole wheat or rye

FAQ: Sourdough starter smells like acetone

Can I bake with a sourdough starter that smells like acetone?
Yes, but it’s usually weaker and more acidic. One or two refresh feedings improve rise.

Is an acetone smell dangerous?
No. It usually indicates hunger, not spoilage. Mold or pink/orange discoloration is dangerous.

Why did my starter suddenly smell like nail polish remover?
Most often due to warmer temperatures, missed feedings, or a feeding ratio that’s too small.

The “Just Fix It” Cheat Sheet

If your starter smells like nail polish remover:

• Keep 20g starter
• Feed 60g water + 60g flour (1:3:3)
• Keep at 72–78°F (22–26°C)
• Feed again at peak
• Repeat 2–4 times

This resolves the issue in most starters within 48 hours.