Sourdough starter troubleshooting: What does it take to kill your starter?

“Did I kill my starter?” This is a surprisingly common sourdough question on our Baker’s Hotline. Novice and experienced bakers alike worry about the viability of their starters and call us for sourdough starter troubleshooting advice.

For many sourdough bakers, the underlying biochemistry at work in their starter remains a bit of a mystery. Thankfully, it’s quite possible to bake great sourdough bread while still being a little fuzzy when it comes to what’s actually happening in that little jar of starter.

The 6 to 10 days it takes to create a healthy and mature sourdough starter from scratch requires slightly more attention to “death threats,” because a fledgling starter hasn’t yet developed the defenses that characterize a mature starter. But once your starter is fully developed, it’s really pretty darn hard to kill.

And if you’ve purchased a sourdough starter from us, rest assured that it’s a mature specimen that will stand up well against unwanted bacteria or mold.

Sourdough Starter Troubleshooting via @kingarthurflour

Things that WON’T kill your sourdough starter

METAL: Stirring your starter with a metal spoon or placing it in a metal bowl won’t kill your starter. While we don’t recommend making or keeping your starter in contact with reactive metals like copper or aluminum, stainless steel is harmless. Sourdough Starter Troubleshooting via @kingarthurflourMILD NEGLECT: Missing a feeding or not timing the feedings exactly 12 hours apart won’t even come close to killing your starter. Please don’t ever set your alarm to get up in the middle of the night to feed your starter!

INCORRECT FEEDINGS: Feeding your starter the wrong amount of flour or water won’t kill it. While your starter may seem too dry or too wet, and may not rise the way you expect, no permanent damage has been done. You can correct its consistency by adding a little more flour or water, and then being more careful the next time you feed it.

BRIEFLY FREEZING YOUR STARTER: While there’s some dispute among sourdough enthusiasts about the benefits and/or dangers of freezing sourdough starter, a brief period in the freezer isn’t likely to kill a fully developed starter.

I recently froze a portion of my well-maintained starter a few hours after it was fed. Three days later I thawed it out at room temperature and let it continue to ferment. It was definitely sluggish at first, but after a second feeding it rose well and had a good aroma.

That being said, too much time in the freezer will definitely damage some of the wild yeast in your starter, and is also likely to kill off some of the friendly bacteria that contribute flavor. If you need to put your starter on hold for an extended time, we recommend drying your starter.

What does it take to kill a sourdough starter? When is it time to give up and start over? Click To Tweet

Things that WILL kill your sourdough starter

HEAT: If you allow your sourdough starter to ferment in the oven with the light on to keep it warm, and then forget it’s in there and turn on the oven, it’s unlikely your starter will make it out alive. Yeast dies at 140°F, and it’s likely that your sourdough starter will suffer at temperatures even lower than that. It’s best to maintain your starter at comfortable room temperature (around 70°F), though a little higher or lower won’t hurt anything.

SEVERE NEGLECT: If you neglect your starter long enough, it will develop mold or signs of being overtaken by bad bacteria. Mold can appear in various colors and is typically fuzzy in appearance. Bad bacteria is generally indicated by an orange or pink tinge or streak. Once your starter has lost its natural ability to ward off intruders, it’s time to start over.

Sourdough Starter Troubleshooting via @kingarthurflour

How to tell if your starter has gone bad

“Hooch” is the liquid that collects on the top of your starter when it hasn’t been fed in awhile. This liquid is the alcohol given off as wild yeast ferments. The presence of hooch isn’t a sign that your starter is in danger. However, it does indicate that your starter is hungry and needs to be fed.

When your starter is neglected for an extended period, the hooch tends to turn from clear to dark-colored. We get lots of calls from sourdough bakers worried about the safety or danger of various hooch hues. Is gray bad? What about brown or black? Surprisingly, none of these colors indicate that your starter has spoiled.

Sourdough-Starter-Troubleshooting via @kingarthurflour

See the orange streak? This starter shouldn’t be saved.

However, if you see a pink or orange tint or streak, this is a sure sign that your sourdough starter has gone bad and should be discarded. The stiff starter above was left out at room temperature for two weeks. It’s definitely time to throw it out and start over.

Sourdough starter troubleshooting: points to remember

1. Well-maintained mature sourdough starters are extremely hardy and resistant to invaders. It’s pretty darn hard to kill them.
2. Throw out your starter and start over if it shows visible signs of mold, or an orange or pink tint/streak.

I hope you’ll share your own sourdough starter questions and discoveries below. There’s always more to learn when it comes to sourdough!

And please check out part 2 of this sourdough starter troubleshooting post!

Barbara Alpern

Long time professional artisan bread baker, caramel maker and member of our Baker Specialist team, Barb grew up in Ann Arbor, Michigan and has four grown sons. She has baked in Michigan, Maine, Vermont, and Texas (if you count baking cookies for her son's wedding!).


  1. brooke

    I am in Day 2 of my King Arthur starter.

    It is super sticky–do you have any tips on how to get the discard out of the crock I bought from you?

    Thank you.

    1. Barbara Alpern, post author

      Hi Brooke, I’m not sure if you’re creating your starter from scratch, or on the second day of feeding the starter we sell, but in either case a good silicone spatula should work well to remove the discard. It sounds like your starter may be a bit thicker in consistency than is ideal, which can make it harder to divide. It’s easy to add extra flour if you’re measuring by cups, and this could result in a thicker consistency, so for best results we recommend either weighing your ingredients or using this method to measure your flour by volume. Right after feeding the starter should have a pasty, but stirrable consistency. After the starter has risen to its highest point it should be thinner in texture–more like a thick pancake batter. If you continue to have difficulties with the consistency of your starter, please give our Baker’s Hotline a call at 855-371-2253 so that we can help you troubleshoot more directly.

  2. Sara F

    I’m that unfortunate soul who thought it was a good idea to leave her starter in the oven with the light on…and who put a note on the oven so her husband wouldn’t turn it on…but the note fell off. And, you can imagine what happened next…
    I pulled the starter out ASAP, I’m not sure what temp it got to. Is there a good way to know if it’s still viable at this point? Over 24 hours later, it smells yeasty and is bubbly in the fridge but I’m just not sure…Any advice would be great!

    1. Barbara Alpern, post author

      Hi Sara, I would give it a day or two of feeding it twice a day at room temperature and see how it performs. If it’s reliably doubling in size after 6-8 hours and continues to have a pleasant aroma, then it sounds like it escaped any permanent damage. I’m crossing my fingers that your starter survived the heat!

    1. Barbara Alpern, post author

      Hi Lori, room temperature (I’m thinking 70 degree) water works fine, but if you house stays in the 60’s this time of year it might be helpful to use slightly warmer water in the 80’s. I’m sure your starter is fine and will just ferment a little more slowly if you fed it cooler water than is ideal.

  3. Sam Pentz

    Hello, my starter developes a thin line of liquid between the bubbles on top and the starter what does that mean?

    1. Barbara Alpern, post author

      Hi Sam, it sounds like the thin line of liquid is some form of hooch, which typically develops when the starter has fallen and is in need of another feeding. It’s also common to see lots of small bubbles on the surface of your starter after the starter has fallen, so it may be that the alcohol that is a byproduct of fermentation is beginning to collect on the surface, along with the small bubbles that escape from the starter as it collapses. Neither of these are worrisome signs, but may just mean that your starter is ready for another feeding.

  4. Jordan

    I purchased a King Aurthur fresh starter a few days ago. We are having sub zero temps here. Is there chance shipping could have killed the starter? I’m following the instructions to a T, but no rise hardly any bubble and the wonderful yeasty beer aroma the oringal starter had is gone.

    1. Barbara Alpern, post author

      Hi Jordan, I wouldn’t worry too much if your starter doesn’t have quite the aroma you’re used to, but if it’s not bubbling and rising, please give us a call at 855-371-2253 and we’ll be glad to troubleshoot and send you a new starter if necessary. A brief freeze shouldn’t cause your starter any permanent harm, but if it’s not working for you then we will happily replace it.

  5. Maria

    Hi. When I was devloping my starter, I kept it in the oven with light on. The oven was turned on, and my starter was left in the oven for a bit. It’s no longer bubbly and rising. Can I add another pack of yeast (mixed with warm water and pinch of sugar) to revive, or is it a lost cause?

    1. The Baker's Hotline

      Oh no, Maria! Unfortunately, it sounds like your starter is past the point of no return. Temperatures over 140°F will kill yeasts. Since you’re no longer getting bubbles, it seems that this is what happened to your starter. On the other hand, you’re lucky in one way: since you’re experienced at maintaining a healthy starter, it shouldn’t be too challenging to start afresh. Our Sourdough Baking Guide can help you get started with creating a new starter, and within a week or two you should be ready to bake again. Kat@KAF

  6. Kristen

    So I followed the KAF guide in starting my sourdough starter. Everything was going well but after a week I noticed that it wasn’t yet as bubbly as it should be and it wasn’t rising at all after feedings. I tried doing 2oz water and 2oz wheat flour, but it didn’t seem to have an effect. Then, I figured my house was far too cold (it gets down to 60 at night), so I put it in the oven with the light on. Now my starter is bubbly and it rises after being fed, but it’s lost it’s sour aroma. It just smells like yeast now. What can I do to troubleshoot this?

    1. Barbara Alpern, post author

      Hi Kristen, that was smart thinking realizing that your starter would benefit from a little warmer environment! I’m glad to hear that it’s rising nicely now. I wouldn’t worry too much if you don’t detect a sour aroma. It sounds like your starter is doing what it’s supposed to do, and if you’ve been feeding it for at least 10 days, it’s probably time to start baking with it. We’ve found that maintaining a healthy starter means nurturing an environment that promotes a balance of both yeast and lactic acid bacteria, and that flavor development is best tackled during the dough phase. If you’re looking for more sour flavor in your bread, look for recipes that call for overnight refrigeration of the dough, and a small percentage of whole grain flour (particularly rye flour), both of which can enhance sour flavor. Our Pain Au Levain recipe provides both these opportunities for developing more sour flavor. For more information on how to refrigerate the shaped loaf overnight and other sourdough techniques, you may enjoy our Artisan Sourdough Bread Tips series of blogs.

  7. Everton martins

    hello, I’m on day 6 of making my own starter and it was very active, raising up to the top of the jar within 6 hours or so. I was feeding every day at 7am but one day I went to feed it and it has collapsed completely during the night. I’ve done the normal feeding but it didn’t bubble even after 8h. Did it die? There was no hooch on it btw. thank you

    1. Barbara Alpern, post author

      Hi Everton, it’s normal for your starter to rise to a high point as it ferments and then slowly fall back to its original height if it isn’t replenished or fed. Falling isn’t a sign that your starter has died, though it is a reminder that it needs to be fed. Has your starter returned to rising and bubbling, or are you still seeing no bubbles? While collapsing during the night wasn’t necessarily a bad sign, no bubbles is. If you’re still seeing no bubbling it may be time to start over. You may want to give our Baker’s Hotline a call at 855-371-2253 so that we can help you troubleshoot more directly.

  8. Anna Ramos-Weese

    I am new at this and an experienced baker gave me the starter but is in FL right now. 1st question: When I take it out of fridge to feed, do I stir it first before i remove the cup to give away or discard?
    2nd question: When I left it out of fridge for 5 minutes it began to grow right in front of my eyes. Is that bad?
    3rd question: When its in the oven the last couple times it over flows the jar. Is that bad?
    4th question: I want to bake bread tomorrow and today is the day I am supposed to feed it. What steps do I take now?
    I should mention the hootch is clear.

    1. Barbara Alpern, post author

      Hi Anna, it sounds like you just have a very healthy and active starter, which is all good! Yes, stir the starter before discarding. When you say “when it’s in the oven” it over flows the jar, I’m assuming you only have the oven light on? There’s no need to warm the starter at higher than 80 degrees, and I’d be careful not to go too much higher than that. If your starter is over flowing the jar you may just need to get a larger jar. For our starter that is maintained at 12 ounces, a quart-sized wide mouth jar works well, but if you’re building the quantity of your starter I would do this in a larger container. When preparing your starter to bake with after refrigeration it’s helpful to give it a day or two of twice a day feedings at room temperature. Since your starter is so active I would just feed it the morning and evening before baking the following day. If you need to build the quantity of your starter because your recipe requires more than one cup (8 ounces by weight) of starter, you can do this during the evening feeding by saving twice as much starter 1 cup (8 ounces) and feeding it 1 cup (8 ounces) of water and 2 scant cups (8 ounces) of flour.

  9. Dorothy

    Hi. I am on Day 3 of a starter and there are blue/green streaks on the top. The rest looks fine, but I’m worried that the blue/green streaks are bacteria or mold. Any advice? Should I just start over? I’m storing mine in a plastic (food-safe) quart container.

    1. Barbara Alpern, post author

      Hi Dorothy, since you’re so early in the process I would start over. Be sure to wash everything in very hot water and dry thoroughly and you shouldn’t experience this issue again. I’m not sure if what you saw is mold or bacteria, but it’s probably best to be on the safe side.

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