Beginner Guide
What Does an Active Sourdough Starter Look Like?
Bubbly, doubled, domed, and slightly tangy-smelling — here's exactly what a ready-to-bake starter looks, smells, and feels like.
An active, ready-to-bake sourdough starter has roughly doubled in size, is full of bubbles throughout, has a domed or slightly collapsing top, and smells pleasantly tangy and yeasty. If it passes the float test (a spoonful floats in water), it's at peak and ready to use.
The signs of an active starter
| Sign | What you'll see |
|---|---|
| Volume | Doubled (or more) since feeding |
| Bubbles | Many, throughout, not just on top |
| Top | Domed at peak, then flattening |
| Texture | Light, airy, billowy |
| Smell | Tangy, yeasty, slightly sweet |
| Float test | A spoonful floats |
Timing the peak
After feeding, a healthy starter rises over several hours to a high, domed peak, then slowly begins to recede. The best time to bake is at or just before peak — fully risen and bubbly, before it collapses. Mark the jar with a rubber band at feeding time so you can see the rise.
The float test
Drop a small spoonful of starter into a glass of water. If it floats, it's full of gas and ready to bake. If it sinks, it needs more time or another feeding. It's a quick confidence check, though not infallible.
What a starter looks like at each stage
- Just fed: thick, smooth, few bubbles, sits low.
- Rising: expanding, bubbles forming, lightening.
- Peak: doubled, domed, very bubbly — bake now.
- Past peak: flattened or sunken, possibly hooch — feed before using.
What you don't want to see
- Fuzzy mold (green, black, pink) — discard and restart.
- Bright pink or orange streaks — discard.
- (A thin gray liquid is just hooch — harmless; stir or pour off and feed.)
Frequently asked questions
How long does it take to become active after feeding?
Usually 4–8 hours at room temperature, depending on starter strength and kitchen warmth.
My starter bubbles but doesn't double — is it ready?
Not quite. Bubbles plus reliable doubling is the standard. Keep feeding to build strength.
Does the smell tell me anything?
Yes — pleasantly tangy and yeasty is healthy. Strong acetone or nail-polish smells mean it's hungry; feed it.
Catching your starter at peak is the difference between a great loaf and a flat one. SourdoughAI learns your starter's rise time and tells you the exact window to use it.