How to Read Your Sourdough Starter — Understanding What It's Telling You
Share this article
One of the most useful skills in sourdough baking is learning to read your starter. A starter communicates its state through appearance, texture, smell, and behaviour — and once you know what to look for, you'll always know exactly what it needs and when it's ready to bake with.
The Rise and Fall Cycle
After feeding, a healthy starter goes through a predictable cycle:
- Lag phase (0–2 hours): Nothing visible. The microbial population is warming up and beginning to consume sugars. Don't panic — nothing is wrong.
- Rising phase (2–8 hours at 22°C): Bubbles appear on the surface and sides of the jar. The starter begins to expand upward. The texture loosens as CO2 forms inside the dough.
- Peak (varies by temperature): The starter reaches its maximum height. It will be domed on top, fully aerated, and alive with bubbles throughout. This is when it's at maximum leavening power and ready to use.
- Fall (after peak): The starter begins to collapse. You'll notice the sides of the jar show a "tide mark" where the starter was at its highest point. It's now past peak and needs feeding again or will become too acidic.
Mark the starting level with a rubber band after each feed. This lets you track the rise and fall cycle precisely without guessing. Our starter jar has a measurement scale on the side for exactly this purpose.
How to Spot Peak Activity
Peak is characterised by:
- Maximum height in the jar — the starter won't rise further
- Domed top surface (slightly convex)
- Bubbles visible throughout when you look through the glass
- Light, airy texture when you stir it — not heavy and dense
- Tangy, lively smell — yeasty and mildly sour
- The float test: a teaspoon dropped in water floats (though this is less reliable than the other signs)
At peak, the starter should feel light and almost fluffy compared to just after feeding. If you stir it, it'll feel much less dense. This is the moment to use it for baking.
Reading the Bubbles
Bubbles tell you a lot about your starter's health:
- Small, even bubbles throughout: Healthy, active fermentation. Good sign.
- Large bubbles on the surface only: Starter is past peak and beginning to collapse. Feed it.
- No bubbles at all: Either too cold, too soon after feeding, or the starter needs attention. See our guide Why Isn't My Starter Rising?
- Extremely large holes throughout: Starter is very over-fermented — feed immediately at a higher ratio (1:2:2).
What the Texture Tells You
Run a spoon through your starter after feeding and again a few hours later:
- Just after feeding: Heavy, thick, smooth — like a very thick batter
- During rise: Lighter, slightly stretchy, starting to loosen
- At peak: Light, airy, almost mousse-like — pulls and stretches easily
- Past peak: Starts to become liquidy and dense again as the gluten degrades
The Tide Mark
After the starter falls, you'll see a mark on the inside of the jar showing how high it rose. This is one of the most useful indicators of your starter's health. A starter that doubles in size (rises 100% above the starting level) within 4–8 hours at 22°C is very active and healthy. A starter that rises 50% is still active but may need a few more consistent feeds to reach full strength.
Temperature and Timing
The timing of the entire cycle is heavily influenced by temperature:
- At 18°C: peak in 12–16 hours
- At 22°C: peak in 6–10 hours
- At 26°C: peak in 4–6 hours
- At 30°C: peak in 2–4 hours (watch carefully — it can collapse quickly)
This is why understanding temperature is essential for timing your bakes. Full guidance in our Starter Maintenance and Troubleshooting guide.
When Your Starter Is Ready to Bake
Use your starter within 30–60 minutes of peak for maximum leavening power. If you're not ready to bake immediately, refrigerate it to pause the fermentation. When it's time, build your levain from the starter at peak and let it ferment fully before adding to your dough. Our Classic Sourdough Bread recipe walks through levain preparation step by step.
