Sourdough Float Test: Is It Really Necessary?

You have probably heard about the float test for sourdough?

If you haven't, here's a short explanation:

The sourdough float test involves taking a scoop of unstirred sourdough starter and dropping it into a glass of water to see if it floats.

It's said that if it floats, your sourdough starter is ready to bake with.

If it sinks, it's not ready.

But is this test really necessary or accurate? Or is there a better way to measure the readiness of your sourdough starter for baking bread?

What Is The Sourdough Float Test?

The float test for sourdough is essentially one way that people use to tell if their sourdough starter is ready for baking.

It entails dropping a spoon of sourdough starter into a glass of water to see if it floats.

If the scoop of sourdough starter floats, it is said that the sourdough starter is ready to bake with.

Now, as you can imagine, there are many other questions that would need to be asked to ascertain whether a sourdough starter is indeed ready to raise bread.

In the first instance, the age of the sourdough starter is essential. Anything before 2 weeks is definitely not ready to bake with.

Once your starter is passed 2 weeks old, it would need to meet these signs of bake readiness.

Sourdough starter should be at minimum 2 weeks before you bake with it. Realistically, it will be several months old before it is baking consistently great sourdough bread.

The Problem With Sourdough Float Test

The sourdough float test isn't the best or most accurate way to measure whether your sourdough starter is ready for baking.

The test can easily show a false positive or indeed false negative.

This test really only shows whether your sourdough starter can hold gas.

A sourdough starter that is young (that is prior to 2 - 4 weeks old) could pass this test, but still not be ready to raise sourdough.

Equally, a sourdough starter that is 4 to 6 months old, doubling consistently and is making sourdough rise could fail the float test.

A false negative can occur if the sourdough starter has been mishandled or is being tested past its peak.

Check out this full guide to whether your sourdough starter is ready to bake with.

Do You Stir Sourdough Starter Before the Float Test?

If you are going to proceed with the float test, it's important you do not stir the starter first.

If you stir the sourdough starter, you will disturb all the gas bubbles expelled by the yeast and the starter will not be able to float at all.

It will look stretchy and stringy, but lack the bubbles necessary to float.

To perform the test properly, it's important you gently scoop the starter from the top of the jar, being careful not to disturb the integrity of the starter.

The gas bubbles need to be intact to make the starter float.

Do not stir your sourdough starter before performing the float test - scoop up those gorgeous bubbles!

What Happens If Sourdough Starter Does Not Pass The Float Test?

If your sourdough starter does not pass the float test, it's not the end of the world.

Here are a few questions to ask yourself, so you know the next step in the process:

Is your sourdough starter less than 2 weeks old? If it's less than 2 weeks old, keep feeding twice a day for a few more weeks and then reassess the readiness using these markers.
Is your sourdough starter more than 2 weeks old? If it's more than 2 weeks old but not floating, check these signs of starter readiness and if it meets these, proceed to baking (you can use this simple sourdough recipe).
If your starter is older than 3 months and not passing the float test, you could try boosting it with these 5 tips for boosting your sourdough starter.

Other reasons your starter may fail the float test, but still be viable for baking:

the starter was stirred prior to performing the test
you haven't fed the starter prior to performing the test
the starter is past it's peak, but is still viable (false negative)
you're using a flour that does not have a strong gluten structure (like rye or whole wheat).

Your sourdough starter doesn't have to pass the float test to bake amazing sourdough bread - however, it does need to pass other signs of maturity.

Hydration Affects Sourdough Float Test

If your sourdough starter is a little runny or has a higher hydration than 100%, it typically will not pass the float test.

It is generally better for your sourdough starter to be a little thicker, rather than watery.

You will find that it rises better when it has the consistency of warm peanut butter.

This consistency will also allow the starter to hold onto the gas bubbles more easily and thus float in water.

Type of Flour

They type of flour you use to create your sourdough starter will affect whether that starter will float in water.

This is because some flours, such as rye or whole wheat, may not allow the starter to develop the strong gluten network needed for the starter to float.

This doesn't mean that it will not allow your bread dough to rise once it's ready to bake with.

If your sourdough starter won't float, it may well be due to the type of flour you are using.

You can read more about the best flour for sourdough bread here.