Sourdough Starter Not Floating in Water — Is It Really Not Ready?
Either you're testing past peak (most common) or your starter just doesn't carry enough trapped gas to float — both fixable.
Your starter looks active — it's doubling between feedings — but a spoonful dropped in water sinks. You're not sure whether to bake with it.
What it looks like
- Visible doubling or tripling in the jar after feeding
- Lots of bubbles on the surface and through the body
- A spoonful drops to the bottom of a glass of water and stays
- Or floats briefly and then sinks within seconds
Why this happens
Past peak
The float test is most accurate when starter is at peak — domed top, just before it falls. A spoonful taken from a starter that has already fallen has released most of its gas and will sink even though the culture is healthy.
Wet, thin starter
Starters above 100% hydration are too loose to trap large bubbles. Tightening to 100% hydration (or even 80%) often makes them float reliably.
Whole-grain or rye starters
Rye and whole-wheat starters often don't float well because the bran weighs them down. They can still bake beautifully — the float test is unreliable for them.
Just not ready yet
A new starter that doubles but sinks might still be building yeast population. Give it another week of consistent feedings.
How to fix it
Mark feeding height and test at peak
Use a rubber band on the jar to mark where the starter sat after feeding. Test the moment it's tripled and domed — that's the best-case scenario for a float test.
Switch hydration to 100% or lower
If your starter is at 110% or 120% hydration, drop to 100%. Thicker starter traps more gas.
Skip the float test for rye/whole-grain starters
Watch for a dome, big bubbles, and reliable doubling instead. The float test was designed for high-extraction white-flour starters.
Try the poke test on dough instead
If the dough rises 50% and a poked indentation springs back slowly, it's ready. More accurate than the float test for whole-grain starters.
Preventing it next time
- Be patient with new starters. Most need a full two weeks.
- Time your bake around peak, not the clock.
- Mark every feeding height. Predictable rise time = predictable peak.
Most starter problems show up in the data.
Sarah's Sourdough — the iOS app — logs every feeding, photographs every rise, and predicts peak by your kitchen temperature. Problems become visible weeks earlier.
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