Does the Float Test Work?
As sourdough starter matures, it releases small carbon dioxide bubbles. These bubbles often become trapped within the gluten network of the flour and water mixture, giving the starter a lighter, fluffier consistency. The longer your starter rises, the more gas becomes trapped in the mixture.
The float test is a technique to see whether the starter has trapped enough gas to adequately lift your bread dough.
To perform the float test, simply spoon some of your starter into a cup of water. If the blob sinks straight to the bottom, the starter has not developed enough to adequately trap carbon dioxide. If it floats on the surface of the water, your dough has enough carbon dioxide to lift your bread.
In theory, anyway.
Why Isn’t It Reliable?
The float test works well enough for some recipes, but it does have its drawbacks. The float test isn’t reliable in a few different situations, and if you rely too heavily on it to determine whether you should bake, you might end up with a flat loaf.
False Positives
A false positive happens when a starter traps enough carbon dioxide to float. However, it doesn’t necessarily mean you should put it in your bread just yet.
Some flours, such as whole meal and rye, hold onto gas better than others. A rye starter may be more likely to float than an all-purpose one.
Additionally, not all starters are fed to 100% hydration. A stiffer starter, for example, can hold more gas than a liquid one, resulting in a false positive.
False Negatives
A false negative occurs when a fully mature starter sinks to the bottom, giving the impression that it’s not ready to bake. However, if you were to put it in your bread, you may still see a beautiful rise and oven spring.
High hydration, or liquid, starters have more water than flour. When dropped in even more water, the starter immediately starts to break down, resulting in a sinking negative.
Additionally, sourdough starters are delicate. If you are rough when handling your starter and dropping it into the water, you may knock out the gas that would otherwise make your starter float.
What Should You Do Instead?
Knowing when your starter is ready to bake is an art, which is why many bakers recommend using the float test. It’s fast and easy to understand.
To find out what you should do instead, you can read the rest of the article at Breadbythehour.com