21 Common Sourdough Starter Problems with Solutions

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Now that I’ve been baking sourdough bread for more than a decade, and maintaining my starter for just as long, I wanted to put together a comprehensive place to talk about common sourdough starter problems. In addition to my own experience creating, maintaining, and refreshing a starter twice a day for over ten years, I’ve helped readers troubleshoot for just as long.  To compile this list, I went through over nine years of emails from readers, as well as several of my top sourdough starter posts here at The Perfect Loaf, to find the most common questions that have come up. No matter what level of baker you are, chances are one of the following 21 common starter questions has at least crossed your mind.

First, if you haven't yet created a sourdough starter, be sure to read my guide to creating a starter from scratch in seven simple steps. It might also be helpful to give my new baker, start here guide a read through if you're new to baking sourdough bread; it will take you from starter creation to baking your very first loaf of bread.

The Perfect Loaf Sourdough Starter Illustration
Michael Hoeweler

21 Common Sourdough Starter Problems

Use the table of contents below or at the right (on a desktop) to quickly flip to a question or problem that interests you.

  1. What helps a struggling sourdough starter?
  2. How do I know if I killed my sourdough starter?
  3. What if my starter smells bad (and what does “good” smell like)?
  4. What if I see mold in my starter?
  5. Why does my sourdough starter rise and then fall?
  6. My starter doesn't rise very high in its jar; how can I get it to rise higher?
  7. Is a sourdough starter supposed to be liquidy (or runny)?
  8. Why doesn't my sourdough starter have big bubbles?
  9. I ran out of the flour I use to feed my sourdough starter; can I use a different flour?
  10. How do I make my sourdough starter more active?
  11. How do I make my sourdough starter more (or less) sour?
  12. My starter forms a thin, clear layer on top; how do I fix that?
  13. Do I have to discard some of my starter each time I feed it?
  14. I can't keep my starter at room temperature; can I use the fridge?
  15. What if I miss feeding my sourdough starter?
  16. My starter jar is gross; how often should I clean it?
  17. Can I use tap water to feed my starter?
  18. My starter doesn't pass the float test; what should I do?
  19. Can a sourdough starter be gluten-free?
  20. How can I convert a stiff starter to a liquid starter (or liquid to stiff)?
  21. What are sourdough starter feeding ratios?

Let's look into each of the above common sourdough starter problems and their solutions and/or recommendations.


1. What helps a struggling sourdough starter?

Most commonly, the issue here has to do with temperature (which is very important). If your sourdough starter is kept at a low temp, even 70°F (21°C), it will slow fermentation activity and appear to be sluggish, taking longer to rise and progress through the typical signs of fermentation. The solution: keep it warm. Around 74-76°F (23-24°C) would work, and you'll see an uptick in fermentation activity (and, in my experience, flavor).

Aside from temperature, if I ever experience any issues with my starter, I'll often treat it as a sick child and give it a little extra attention, care, and some healthy food. For my starter, what I find works is to keep it warm, feed it with a portion of whole-grain rye flour (due to the increased nutrients present in the flour), and give it timely feedings of fresh flour and water right when it's ripe.

For example, to help a struggling sourdough starter, I'd give it a week's worth of feedings with this makeup:

IngredientExample WeightBaker's Percentage
White flour (all-purpose flour or medium protein bread flour)30g30%
Whole-grain rye flour (or whole wheat flour)70g70%
Water100g100%
Ripe sourdough starter carryover20g20%

I'd give my starter two feedings per day, while also keeping it warm (around 76°F/24°C), for a full seven days. Once fermentation activity picks back up and it stabilizes (with the same rise and fall each day), you can then switch to any maintenance recipe you normally follow.

This would mean my starter is fed near a 1:4:4 ratio for a while (technically, a 1:3.33:3.33), which I find best for my normal maintenance. But for a 12-hour feeding interval at a warm temperature, I find this keeps my starter strong and healthy.

See my YouTube video on how I maintain my sourdough starter (and have done so for over 10 years):

2. How do I know if I killed my sourdough starter?

Oh, it's so difficult to kill a sourdough starter! I've had readers write in about having left a starter on their counter for a week or it in the fridge for a month or more without feeding it, and once they’ve given it a few consistent feedings, it's sprung back to life, ready to make delicious bread.

As long as the temperature doesn't get too high—yeasts begin to die off around 120°F (48°C)—your starter can handle a wide range of temperatures. I do prefer to keep my starter well below 85°F (29°C), I like 74°F (23°C), though, to ensure it isn't overly active and for the best balance of yeast and bacteria.

3. What if my starter smells bad (and what does “good” smell like)?

What a bad starter might smell like: Use your initial reaction to smelling your starter as a guide: if it makes you recoil in disgust, it might not be in a good place, and in this case, I’d look for signs that mold (see next question) is present. Usually, this also presents as an aroma like spoiled or rotten food.

What a good starter might smell like: Bakers often say their healthy starter might smell a bit like sulfur, a little musty, a little like ripe cheese or yogurt. Personally, when I use whole grain rye flour in my starter, at the end of its refreshment cycle it’ll smell pungent and musty, but it never makes me feel disgusted or off-put. It has a unique aroma that I’ve come to identify with my starter.

4. What if I see mold in my starter?

Typical signs of food spoilage and mold include pink, orange, or green colors, white fuzzy spots, or sometimes areas that are darker with white areas on top. If you see any of these signs, I would recommend throwing your starter away and creating a new one.

Follow my guide to creating a starter, and in only seven days, you’ll have a fresh and healthy one that’s ready for baking.

The Perfect Loaf Sourdough Starter Illustration
Michael Hoeweler

5. Why does my sourdough starter rise and then fall?

As fermentation progresses in your mixture of flour, water, and ripe starter, the byproducts of fermentation, namely gas production, are trapped in the viscoelastic dough and cause it to rise. This rise is expected and is a good indicator of strong fermentation activity. However, depending on the type of flour you are using to feed your starter, it may not rise all that high and fall all that far—and that’s okay. I find the amount a starter rises is not a super important sign of health or strength (see next question for more).

In some cases, I’ve found that some starters never fall, or only collapse a small amount in their jar. Again, this is related to the flour used and is not a bad sign. Use the other signs of fermentation to determine when it’s ripe and needs feeding.

6. My starter doesn't rise very high in its jar; how can I get it to rise higher?

In my experience, the rise height isn’t as critically important as the other signs of fermentation (aroma, consistency, etc.). The height at which your starter rises (and possibly falls) in the jar is highly dependent on the flour you’re using for feedings. For example, using all strong high protein white flour and hydration that’s not excessively over 100% will result in a starter that likely rises very high in the jar. This is due to the protein quality and gas-trapping capability of the white flour. Conversely, flour such as whole wheat or whole rye may not rise as high but will still be perfectly suitable for baking.

7. Is a sourdough starter supposed to be liquidy (or runny)?

It’s not a problem if a starter has a loose and runny consistency, as this texture is a byproduct of a starter’s hydration and the flour used for feedings. If your starter has very high hydration–that is, a large amount of water compared to the total flour–you’ll find it’s more liquidy/runny, compared to a starter with lower hydration.

In my experience, the higher the hydration of a starter, the more fermentation activity you’ll find, assuming all else is equal.

8. Why doesn't my sourdough starter have big bubbles?

Large bubbles are not necessary for a starter to be healthy. Bubbles are a reflection of the flour used for feedings. High protein white flour will typically present more, larger bubbles than whole grain flour (which has less gas-trapping capability). 

9. I ran out of the flour I use to feed my sourdough starter; can I use a different flour?

Absolutely. Any flour that’s suitable for baking can be used to feed your starter. Switch to a different flour for a while, and then once you restock your typical flour, switch back. There’s no need to “ramp up” when switching flour types; your starter will be just fine doing an immediate switch to a different flour.

Read about how I currently feed my sourdough starter ↗

Super active sourdough starter

10. How do I make my sourdough starter more active?

The following will help increase fermentation activity in your starter:

  • Keep your starter warm, 74-76°F (23-24°C) or warmer
  • Use more whole grains in each feeding
  • Feed your starter when it’s ripe (not too early, and not too late)
  • Don’t place it into the refrigerator

11. How do I make my sourdough starter more (or less) sour?

Many think having a very sour starter will result in sourdough bread with a very sour flavor, and while this does help, it doesn’t have as large of an impact as a levain for a particular dough, or the dough’s makeup and baking process.

Compared to a levain, a starter is typically only used in a very small amount when baking (unless you’re using a large starter amount to bake with directly). This small starter is used to make a much larger levain, which is where efforts can be directed to increase sourness.

Regardless, to make a starter or levain sourer, you can:

  • Increase whole grains
  • Keep it warmer (80°F/26°C)
  • Use or feed it after it’s ripe

Read about the differences between a levain and a sourdough starter ↗

12. My starter forms a thin, clear layer on top; how do I fix that?

This thin, watery layer (sometimes called “hooch”) is usually nothing to worry about. When this layer is present, you might find the aroma of your starter is close to nail polish remover, or just very pungent. To remedy, simply pour off the clear liquid or stir it back into your starter. Then, discard and give it a feeding as usual. If you see hooch form often, it can be a sign your starter needs to be fed earlier.

13. Do I have to discard some of my starter each time I feed it?

Sourdough waffles
Sourdough starter discard waffles.

In almost all cases, the answer is yes. If you didn't discard a portion of your starter each time you feed it, two things would happen:

  1. Your starter would grow to an enormous, unmanageable size.
  2. Your starter would likely become more and more inhospitable to the bacteria and yeast we want, as the mixture would become ever more acidic.

Since you're discarding, you might as well use that discard, check out some of my sourdough discard recipes (waffles, pancakes, and banana bread) ↗

14. I can't keep my starter at room temperature; can I use the fridge?

Storing sourdough starter in the fridge
Sourdough starter after 1 week in the fridge.

Since I bake often, I prefer to keep my starter healthy, strong, and active at room temperature. However, it will survive just fine if kept in the refrigerator for one or two weeks. After that time, I find it’s helpful to take it out and give it a feeding, let it ferment for a while on the counter, then place it back into the fridge for another week or two.

I find my starter does not perform well if used directly from the refrigerator; instead, I take it out two days before I want to use it to bake with, give it a few timely feedings, then use it to make a levain before baking. After making the levain, I give it a feeding, let it sit on the counter for one hour, then place it back in the fridge.

Learn how to store your sourdough starter (for short and long term) ↗

15. What if I miss feeding my sourdough starter?

If you miss one of your starter feedings, it'll be just fine. Give it a feeding when you next remember it needs one, and continue with your daily feedings as usual.

However, missing too many feedings in a row can result in degraded performance with your starter as it eventually becomes overly acidic, which can harm the balance of bacteria and wild yeast and result in reduced fermentation activity. If you get way off track, just go back to your schedule for a few days until you see steady, reliable fermentation activity.

16. My starter jar is gross; how often should I clean it?

I like to clean mine as often as necessary to ensure it's not overly gunked up with starter. For me, I typically scoop a small bit of starter into a new jar every two weeks, which ends up being about when my jar gets too crusted with the starter at the top where the lid rests.

Check out my baking tools for my favorite starter jars ↗

17. Can I use tap water to feed my starter?

Any water that's safe to drink is suitable for feeding your sourdough starter.

While it's possible that excessive levels of chlorine may inhibit fermentation, I haven't found this to be a significant issue with an already established sourdough starter.

18. My starter doesn't pass the float test; what should I do?

The float test is not a definitive test for whether a starter is healthy. Why? Take, for example, a starter that’s maintained with 100% rye flour, which has less gas-trapping capability than white flour: it may not ever float.

While the float test can be a good high-level look at the aeration and gas production in your starter, take a holistic approach when assessing starter ripeness or health. Instead of relying on the float test, look to see if your starter has risen to some degree, there are bubbles, it has a sour aroma, and a loose consistency—these are all indicators of ripeness.

19. Can a sourdough starter be gluten-free?

Yes, you can use flour such as brown rice flour or buckwheat flour to create and maintain a sourdough starter. These grains/cereals do not have gluten, but they still provide the sugars and other minerals needed to support fermentation by lactic acid bacteria and yeasts.

Check out some of my favorite flour and baking tools ↗

stiff sourdough starter
Stiff and ripe sourdough starter.

20. How can I convert a stiff starter to a liquid starter (or liquid to stiff)?

Converting between a stiff (50-65% hydration) and liquid (90-110% hydration) starter can be done by simply removing or adding water to the starter, respectively. You do not need to do this gradually over time; you can simply withhold or add water at your next feeding to adjust a starter’s consistency.

21. What are sourdough starter feeding ratios?

Starter feeding ratios work the same way as all baker’s percentages: all the ingredients are related to the total flour in the mixture. With a sourdough starter, sometimes people use slightly different terminology to describe the flour, water, and ripe starter. I call this “ratio notation” and you’ll often see this represented as something like 1:2:2, which means one part ripe starter carryover to two parts water to two parts flour.

Sourdough starter ratio diagram

As an example, for 12-hour feedings, my starter is typically maintained at 20% ripe starter carryover, 100% water, and 100% flour. Using ratio notation, this would be 1:5:5. To translate this ratio to actual weights, let’s assume I had 20g ripe starter; to calculate how much water and flour I would need, I simply take that 20g and multiply it by 5 for water and flour. This gives me a feeding of 20g starter, 100g water, and 100g flour.

There are many common sourdough starter feeding ratios and any will work. Successful ratios are highly dependent on the flour used to feed a starter and the environment (especially the temperature) it’s kept at.

Read through my guide to baker's percentages ↗


Final thoughts

With the common sourdough starter problems and solutions above, you should now have a firm grip on how to handle just about any problem that might spring up with your sourdough starter. But in addition, the biggest piece of advice I like to give bakers is to simply be observant of your starter each day. With a little attention, you'll learn to spot the signs of when something is “off” and learn how to adapt to any problem that might arise.

See my sourdough starter frequently asked questions for more assistance if you're struggling to keep your starter strong and healthy. Or, see all my sourdough starter guides.

Want to chat about your starter, ask questions, or post pictures of how it's going? Join The Perfect Loaf community!

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