Okay, so you opened your jar of sourdough starter and got hit with something that smelled less like artisan bread and more like a nail salon. And now you’re standing in your kitchen holding that jar at arm’s length wondering if you’ve somehow killed a living thing you were really proud of keeping alive.
You haven’t. I promise.
That smell has a name, it has a cause, and — this is the important part — it has a fix. It makes sense because once you understand what’s going on inside that jar, the whole thing stops being terrifying and starts being kind of fascinating.
Why does sourdough starter smell like nail polish remover?
That sharp chemical smell is ethyl acetate — a byproduct produced when your starter runs out of food and the wild yeast and bacteria inside start breaking down in a different way. Some people call it acetone, some call it nail polish remover, some just call it “wrong.” All of those are correct. It happens when the acetic acid bacteria in your starter shift their metabolic process under stress — specifically, hunger stress.
Your starter isn’t sick. It’s just really, really hungry.
Is a nail polish remover smell a sign the starter is dead?
No — and this is the thing I want you to hear clearly. A starter that smells like nail polish remover is still alive. Dead starter doesn’t smell like anything particularly alarming. It just goes flat, stops bubbling, and eventually gets fuzzy in a way that has nothing to do with fermentation and everything to do with actual mold.
Ethyl acetate smell means there’s still active microbial life in that jar. They’re just unhappy. Feed them.
What causes the starter to get to this point?
A few things can push a starter toward that chemical smell. The most common is a long stretch between feedings — if you left it on the counter for several days without feeding it, or it’s been in the fridge for a few weeks untouched, you’re going to get that smell. A too-warm environment can speed up fermentation and burn through the available sugars faster than normal, leaving the bacteria with nothing to eat sooner than expected.
High hydration starters tend to get there faster than stiffer ones. It makes sense because there’s more liquid, more activity, more rapid fermentation — and a shorter runway before things go sideways.
How do you fix a sourdough starter that smells like acetone?
Feed it. That’s it. That’s the whole fix.
Discard about half, then feed it a roughly equal ratio of flour and water by weight. Room temperature water, whatever flour you normally use. Set it somewhere warm — around 75°F is ideal, according to King Arthur Baking’s starter troubleshooting guide — and let it do its thing. Within 12 to 24 hours you should see bubbles. Within 48 hours the smell should be completely gone, replaced by that tangy, yeasty, slightly funky-in-a-good-way smell you actually want.
If it’s been neglected for a really long time — like weeks in the fridge — you might need two or three feeding cycles before it’s fully back in fighting shape. That’s normal. Don’t panic.
Does the liquid layer on top mean the same thing?
If there’s a grey or dark liquid sitting on top of your starter, that’s called “hooch” and yes — it’s related. Hooch is basically alcohol produced during fermentation, and it shows up alongside or sometimes instead of the nail polish smell when a starter is past hungry and into starving. You can stir it back in or pour it off, either works, but then you need to feed the starter immediately.
Hooch and acetone smell are your starter’s two main ways of waving a little white flag. Consider this your sign to pay attention to your feeding schedule.
Can you still bake with a starter that smells off?
Honestly — I wouldn’t, not yet. A stressed starter isn’t going to give you great bread. The yeast activity is low, the microbial balance is off, and you’re going to get a disappointing rise and weird flavor. Nurse it back to health first. Once it’s passing the float test and doubling reliably within 4-8 hours of feeding, then you’re back in business.
If you’ve been struggling to get your starter stable, check out my notes on getting a sourdough starter going from scratch — sometimes the issue goes back further than just one missed feeding.
What should a healthy starter actually smell like?
A healthy active starter smells tangy and yeasty — a little like beer, a little like yogurt, sometimes almost fruity. Different flour types can shift the smell slightly. Whole wheat starters tend to smell earthier. Rye starters can smell really funky in a way that surprises people but is totally fine. The through line in all of them is: it smells like food. Alive, fermented, interesting food.
Nail polish remover is never the goal. Tangy and active is the goal.
And if you’re getting into sourdough for the first time and feeling overwhelmed by all of this, I talked about the parts of sourdough baking nobody warns you about a while back — might be worth a read before your next bake.
The short version is — your starter is fine. Feed it, give it a day, and stop worrying.
Sourdough is remarkably resilient. People revive starters that have been in the back of a fridge for months. The nail polish remover smell feels alarming because it’s so specific and so wrong, but it’s just chemistry doing chemistry things. Hungry bacteria producing ethyl acetate. Feed them and they stop.
Don’t throw that jar away. You’ve put too much time into that thing.
Frequently asked questions
Why does my sourdough starter smell like nail polish remover?
Is my sourdough starter dead if it smells like acetone?
What should I do if my sourdough starter smells like acetone?
Can I still bake bread with a starter that smells like nail polish remover?
What is the liquid on top of my sourdough starter?
How long does it take to fix a sourdough starter that smells bad?
What should a healthy sourdough starter smell like?
