Sourdough starters are among the most forgiving fermented foods, and with a little care and understanding, almost any issue can be fixed.
Below, I’ll explain the most common sourdough starter problems, their causes, and how to solve (or prevent) them.
What’s Actually in a Sourdough Starter?
A healthy sourdough starter is alive with wild microbes—mainly lactic acid bacteria, acetic acid bacteria, and wild yeast. These microbes come from the flour, and we activate them by adding water. When they’re active and well-fed, they convert wheat carbohydrates into flavorful acids and CO₂, which gives your bread rise and flavor.
Microbiologists call sourdough fermentation mixed fermentation. Bacteria and yeast work together, consuming sugars and alcohol to produce lactic and acetic acid, and yeast produces the gases responsible for the rise.
Starting a Sourdough Starter from Scratch? Here’s Why It’s Usually So Wet at First
When establishing a brand-new starter with just flour and water, giving the dormant microbes in the flour plenty of water activity is essential so they can wake up and multiply. That’s why the initial hydration level of my three sourdough starter recipes is high. Find those recipes here:
- How to Make Rye Flour Sourdough Starter
- How to Feed a Sourdough Starter with Bread Flour
- How to Make a Gluten-Free Sourdough Starter From Scratch
- Einkorn Sourdough Starter From Scratch
I think of it like a microbiology lab. When scientists want to culture microbes from a dry sample (like a grain of rice or a speck of dust), we first place it in a liquid broth. Sourdough works the same way. Beginning with a very hydrated starter (something close to a 1:1:1 ratio of flour to water to starter) helps those wild microbes get up and running during the first seven days of establishing it.
Once your starter is bubbly, even if it isn’t rising but you see bubbles, you can transition to a thicker consistency, which will better hold a rise in the jar, pass a float test, and behave more like a bread dough.
Not All Flours Absorb Water the Same
One of the biggest surprises when working with sourdough is how different your starter can feel depending on the flour you use—even when you follow the same recipe. That’s because different flours absorb water at different rates.
Whole wheat and rye flours contain the bran and germ, which act like little sponges and soak up much more water. So whole wheat flour will make your starter thicker and doughier, and it will often hold its rise in the jar for longer. On the other hand, white bread flour and all-purpose flour are mostly made up of endosperm, which absorbs less water. Starters fed white flour tend to be looser, thinner, and more prone to deflating quickly after rising.
Neither is better—they’re just different textures, and that’s an easy fix. If it’s too runny to hold a rise in the jar, just make it thicker by adding more flour.
Feeding Ratio: How Much Starter to Feed?
Once your starter is bubbly and active, you only need a small amount to keep it going.
Here’s my general maintenance ratio:
- 10% starter
- 50% fresh flour
- 40% water
This ratio keeps the acid low and gives your microbes plenty of food without overpopulation. Too much starter (like a 1:1:1 ratio repeatedly) can cause fast acid buildup because the microbial load is much higher. For your starter to keep thriving, you want more food for fewer microbes, not less food for more microbes.
When Is My Starter “Ready” to Bake With?
There’s a lot of confusion about when a sourdough starter is officially “ready,” part of that is because the float test isn’t always reliable, especially for thin and runny starters.
A float test only works if your starter has enough structure (gluten) to trap gas bubbles and hold them in place. If your starter is too watery, even if it’s very active, it will just sink.
If you’re using quality flour and feeding consistently, most starters are microbially ready to bake within about seven days. As soon as bubbles form, feed it a little thicker and watch for signs of rise. The float test becomes a more useful tool once it’s thick enough to trap gas and visibly expand in the jar.
Why Isn’t My Starter Bubbling or Rising?
Starters not rising is the most common concern, especially during the first 7 days of establishing a starter. A few key things might be happening:
- It’s too early – The first 2–3 days are often quiet. Be patient.
- It’s just hydrated – Very wet starters will bubble but won’t hold a visible rise for long. Try thickening it slightly so you can see bubbles better.
- It’s not warm enough – Starters thrive around 75–80°F. Too cool, and they’ll slow down dramatically.
- You missed the peak. A well-fed, thinner starter rises and falls. If you check after it’s peaked, it may have risen but already collapsed. Thicker starters hold a rise in the jar longer so you can see it (and take a picture of it).
💡 Try this tip from my course: Feed your starter more flour or less water to make it thicker, or try a naturally more absorptive flour like sprouted rye. Once your starter is bubbly, you don’t need to measure it; give it an extra spoonful of flour if it’s thin.
What Does Sourdough Starter Smell Like?
A healthy starter smells pleasantly sour, like vinegar, yogurt, or beer. If it smells sharp or strange, here’s what might be going on:
- Nail polish remover or alcohol smell? Alcohol and acetaldehyde are byproducts of yeast fermentation, and they can make your starter smell like nail polish. It’s totally normal, but it’s a sign that your starter needs more oxygen. Stir, feed, and use a loose lid or cloth cover secured with a rubber band. Ensure it’s tight-weave cloth to keep bugs out.
- Funky or putrid odor? That could indicate poor flour quality or microbial imbalance. Switch to organic whole grain flour, stir more often, and ensure you feed consistently every 24 hours, then see what happens.
What’s That Liquid on Top of Sourdough Starter?
That liquid is called hooch; just alcohol yeast produces when your starter is hungry. You can pour it off or stir it in (though I usually pour it off for better flavor balance). It’s harmless, but it means your starter needs to be fed.
The colors of your starter and hooch will vary depending on the flour and microbe mix. Clear, gray, brown, or even purple hooch on top is normal.
Is That Mold?
Maybe. Maybe not. People often confuse dried-out patches or harmless pellicles (dried-out film on top) with mold.
If there is mold, it will look fuzzy and may be green, blue, black, or pink. If you see fuzzy mold or brightly colored growth, toss the starter and start fresh.
It’s always better to prevent mold than try to fix it after the fact. To prevent mold:
- Feed your starter every 24 hours.
- Use clean jars and utensils.
- Transfer to a clean jar every few days.
- Keep the lid clean; yes, cloth lids, too.
- Don’t let it dry out from neglect—especially around the edges. Keep it covered with a solid lid in the fridge, not a cloth lid.
What About Pink or Reddish Discoloration?
A reddish tint can be normal if you’re using 100% rye flour. But if you’re using white flour and see a pink hue, especially near the top or in the hooch, it could be a sign of Serratia marcescens, an unwanted bacteria. It’s best to start over.
Taking a Break from baking? Here’s What to Do
If you’re not baking for a while:
- Feed your starter.
- Let it sit out for 6–12 hours until bubbly.
- Seal with a lid and place in the fridge.
Feed once a week to maintain it—or even less frequently. I’ve revived starters that sat in the fridge untouched for two months. You should also dehydrate your starter for long-term storage and as a backup in case something happens.
How to Dehydrate Sourdough Starter (always to have backup)
- Feed your starter and let it peak.
- Spread a thin layer on parchment paper.
- Dry in a dehydrator at 98°F or until completely dry.
- Store in an airtight container.
To revive: rehydrate with water, feed daily as you would feed an active starter, and give it a few days to bounce back.
Advanced Troubleshooting Tips
If your starter seems sluggish, try one of these:
- Switch flours: Rye, spelt, and sprouted flours have more FODMAPs, encourage microbial diversity, and improve activity.
- Not sour? Add a drop of brine: A tiny spoonful of fermented vegetable brine (like sauerkraut) adds LAB to help balance the ecosystem.
- Bread not rising much? Add yeast: This is a controversial tip, but I’ve done it. Add some organic, natural dry, or instant yeast to balance out the yeast-to-bacteria ratio. And always remember to feed less starter, more flour + water when you discard and feed.
- Make it thicker: A thicker starter will rise more visibly and be easier to track.
- Warm it up: Use a bread proofer or place the jar in a warm spot.
- Add Sugar: A spoonful of honey or organic apple juice helps liven up a sluggish starter. Yeast loves fructose.
Final Thoughts: It’s Hard to Kill a Starter
Really. They’re resilient.
Things that won’t kill your starter:
- Stirring with a metal spoon
- Storing in the fridge
- Changing up the flour
- Forgetting a feeding once in a while.
Things that will kill it:
- Mold
- Neglecting it for days at room temp without feeding
- Using bleached or low-quality flour repeatedly.
As long as you keep feeding it high-quality flour, keep the jar clean, and stay curious, your sourdough starter will likely stay with you for life.
Sourdough Recipes to Try
- My Go-To Homemade Sourdough Pizza Crust Recipe
- Dutch Oven Sourdough Bread Recipe (Master Recipe)
- New York Style Sourdough Discard Bagels (Ready in 4 hours)
Sourdough Discard Recipes
- Double Chocolate Cherry Muffins with Sourdough Discard
- Sourdough Strawberries and Cream Cookies
- Buttery Rosemary Sea Salt Sourdough Crackers
- Honey Cinnamon Sourdough Graham Crackers Fermented Overnight
I used distilled water with cultured starter. Oops. Can I continue with well water when I feed?
If it’s tested and safe well water, sure, filtered well water should work fine.
Hello, enjoyed your article. I’m a newbie, I started on Friday and Saturday my starter barely rose, so I left it till the evening and went ahead and added more flour/water, covered with cloth, then left it overnight. Sunday morning it had risen with bubbles, looked great and had a sour smell. 2 questions: Is it normal to already have the sour smell, I thought it was suppose to take like 7 or more days? Also, Sunday afternoon I noticed liquid in the bottom of my jar, not on the top, is this hooch or something else? Thank you for your time and your insight!
Hello, I’ve always fed my starter KA BF. Recently I noticed brown specks of what look like rye in my flour I immediately freaked out because I’ve never fed it rye. Should I switch flours?she smells fine, almost sweet, is doubling/tripling and besides this I havent noticed fuzzy or discoloration. Is this normal? Thanks.
It’s probably just a harmless variation in the flour! Unbleached flours can naturally have tiny darker specks of wheat germ or bran. Probably nothing to worry about and no need to switch. If it smells fine, looks fine, and is bubbling nicely, then keep doing what you’re doing 🙂