Schwimmtest (Float Test) – When Is Your Sourdough Starter Ready?

How to perform the schwimmtest (float test) to judge sourdough starter readiness, scientific reasons, step-by-step instructions and troubleshooting.

Why This Technique?

A quick, practical check whether the starter is aerated and buoyant enough to leaven dough.

The schwimmtest (float test) checks whether a portion of starter contains enough trapped CO2 in its matrix to float. Floating indicates a balance of active yeast producing gas and an elastic starter structure that keeps gas trapped — both needed to lift dough in proofing [1]. Repeat observations in feeding cycles are more informative than a single pass/fail test [1][2].

✓ Fast and simple check before mixing dough ✓ Non-destructive when done with a small spoonful ✓ Useful confirmation in combination with other readiness signs (doubling, aroma, texture)

Step by Step

Preparation:

Feed your starter at your normal ratio and wait until it shows peak activity according to your usual timetable (volume peak, domed surface, lots of bubbles). Use consistent temperature and feeding routine so the test is meaningful [1][2].

1

Fill a clear container with room-temperature water (not cold).

2

Gently spoon a teaspoon-sized dollop of starter from the very top layer — this area contains the most trapped gas. Use a jar spatula to avoid deflating the sample.

3

Carefully release the starter into the water without pushing it below the surface; watch whether it sinks or floats.

4

Observe for 10–30 seconds. A floating sample that remains buoyant indicates good gas retention; a sinking sample is inconclusive on its own and requires cross-checking with other indicators [1].

🎬 Video Tutorial

Float Test for Sourdough Starter (Demonstration) 📺 Sourdough Techniques ⏱️ 3:12

Short demo showing how to perform the schwimmtest and interpret results.

Alternative Techniques

Rise/Doubling Observation

More reliable for stiff or very loose starters; monitor volume increase in a [glass jar for starter](https://amzn.to/4pWAN8D)

Float Test with Dough Sample

Take a small doughy piece (not pure starter) to test real dough behavior if starter tests are inconsistent

Perform a Test Bake (Butterfly or Small Loaf)

Most definitive: bake a small loaf or use an informal test dough when in doubt

Sources

  1. [1]
    The Perfect Loaf – The Perfect Loaf – Link
  2. [2]
    Plötzblog – Plötzblog – Link