What to Do When Sourdough Starter Not Floating

All great loaves of sourdough bread begin with a good sourdough starter. How do people determine whether it’s good or not? For some, the float test is the only answer. But what happens if your sourdough starter won’t float? What should you do?

Your sourdough starter might not pass the float test if it’s been degassed, you’re using flour with low protein content, or it has too much hydration. This doesn’t mean your sourdough starter won’t work, though. It’s best to look for other signs that your starter is ready for action.

Hello! My name’s Michelle, a self-taught baker that’s been on a ten-year-long journey to become a top-notch baker. Throughout my baking adventures, I have learned the ins and outs of sourdough starters. 

Let’s talk about floating sourdough starters!

What is the “Float Test?”

The float test is a simple test that assesses whether or not your sourdough starter is “ready.” 

Performing the float test is simple: fill a cup with water, add a tablespoon of sourdough starter to the water, and watch to see if it floats. If it floats, the sourdough starter is determined as “ready.” If not, the starter needs more time.

The float test isn’t always an accurate representation of doneness, though. For instance, a baby starter (less than two weeks old) might float, but that doesn’t mean it’s ready to bake. On the other hand, a senior starter may not rise for any number of reasons.

Why is My Sourdough Starter Not Floating (3 Reasons)

Although it might not be 100% accurate, many people rely on the float test. After all, a sourdough starter isn’t exactly the easiest thing in the world. Not only can it be challenging to create, but it is even more complicated to know when it’s “ready.” 

So, what would cause a sourdough starter to sink? There are three main factors.

1. Low-Protein Flour

One of the main reasons why sourdough starters won’t float is because you’ve used flour with low protein content. Although the flour will be able to create a strong gluten network for your loaf of sourdough, it simply won’t have the capacity to float in water.

That said, double-check the protein content of your flour. Bread flour has a high protein percentage, so it should easily float. Flour-like rye? Most rye flour contains 13% or less, which means it’s less likely to float in water.

2. Too Much Hydration

When it comes to making sourdough starters, it’s all about getting it “just right.” For the most part, you should be using a 1:1:1 ratio. For instance, 100 grams of water and 100 grams of flour per every 100 starters.

If you add too much water, you will throw the ratio off. Again, this might not mean that your sourdough starter won’t work when it comes to baking bread. However, it will turn into a gloopy, sloppy mess when introduced to water.

3. It’s Been Degassed

I’ve said it once, and I will say it again: sourdough starter is finicky and can easily become accidentally degassed. 

This can happen in two ways. For one, you might stir the starter before adding it to the water. Mixing, even gently, will cause the starter to de-gas and fail the float test.

Secondly, you may simply be maneuvering the jar too “roughly.” When you pick it up to move it closer to the water, you may accidentally de-gas it. This can also happen by roughly setting the sourdough starter on the counter.

How to Tell if Sourdough Starter is Ready (3 Signs)

Needless to say, many things can affect whether or not your sourdough starter passes the float test. However, these issues may make it so the starter doesn’t pass the float test but can still create a delicious loaf of sourdough bread.

What’s the better option?

Ditch the float test and check for other signs your sourdough starter is ready, including:

1. Bubble Formation

When a sourdough starter is ready to use, there will be a decent bubble formation along the top of the jar. If you see an impressive bubble structure, it’s likely ready to use.

2. Doubled in Size

Feed your sourdough starter as usual. Then, check back in about four hours. Has your sourdough starter doubled in size? Then it’s ready for action!

3. Sour Smell

When the sourdough starter is ready to go, it will have a potent sour smell. Go ahead and give it a whiff! If it’s acidic, has bubbles, and doubled in size, it’s ready to go.

How to Get Sourdough Starter to Float

The best way to ensure that your sourdough starter will float is to follow the 1:1:1 ratio (100 grams water and 100 grams flour per 100 grams starter). Make sure that you’re not adding too much water, as this can cause a runny sourdough starter that won’t hold gas – and therefore won’t float.

Using bread with a higher protein content is also recommended. For instance, bread flour has a higher protein content than rye flour, and will therefore do a better job at holding onto the water and producing the necessary gasses for success.

Lastly, be extra careful when performing the float test. Being too rough with the sourdough starter can cause it to de-gas, which means it will not float. Always be gentle when working with your starter.


Now that you have some troubleshooting under your belt, you can get back to confidently making loaves of delicious sourdough bread! Still not satisfied with this info? Still have some prying questions? Here are a couple of frequently asked questions to check out!

What happens if sourdough leaven doesn’t float?

If your sourdough starter doesn’t float, you can try removing half of the leaven and adding fresh water and flour. This should cause the starter to “wake up” and pass the float test. However, also consider the issues mentioned above, as they will halt your starter from floating.

Do sourdough starters have to pass the float test?

Not necessarily. If your sourdough starter shows signs of readiness, such as a sour scent, a giant bubble formation along the top, and has doubled in size, you likely don’t need to fuss with the float test. 

Is Your Sourdough Starter Not Passing the Float Test?

While most sourdough starters pass the float test, even “ready” and “active” starters can get a false negative. A false negative typically occurs when the starter is made with too much water, flour with too little protein, or it’s been accidentally degassed.

Do you use the float test?

About Michelle
I have been a lover of sweets since day one. This led me on a self-taught baking journey starting at the age of 13. It's been over 10 years since the start of my baking adventures, and I’ve learned a lot along the way. Now, people rave about my delectable treats, whether it’s a chocolate cake or a strawberry crepe.

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