Sourdough Starter: Knowing When It’s Ready to Bake

The most common sourdough problem is not a bad recipe. It is baking with a starter that was not ready. If your loaves come out flat and dense, the starter is usually the culprit. This article shows you how to read your starter accurately, why the popular float test can fool you, and how to bring a sluggish starter back to full strength.

What a ready starter is doing

A starter is a living culture of wild yeast and bacteria. When you feed it fresh flour and water, the yeast eats the sugars and produces gas, and the whole mass rises. “Ready” means the culture is at its peak activity: maximum gas, maximum lift, strong enough to raise a whole loaf.

Peak matters because a starter follows a curve. It rises, plateaus, then falls as the food runs out. Bake with it on the way up or at the top and you get strong fermentation. Bake with it after it has collapsed and much of the yeast power is already spent.

The reliable signs it’s ready

It has roughly doubled

The single best signal is volume. After feeding, a healthy starter at room temperature roughly doubles or triples within 4 to 8 hours. Mark the jar with a rubber band at feeding time and watch for that rise.

It is domed, then just starting to flatten

At peak the surface is domed and bubbly. When the dome flattens or dips slightly in the center, you have hit the top of the curve. That window, right at or just before the flatten, is prime baking time.

It smells tangy, not sharp

A ready starter smells pleasantly sour, yeasty, sometimes yogurt-like. A harsh acetone or nail-polish smell means it is hungry and overdue for a feed.

Why the float test misleads

The float test tells you to drop a spoon of starter in water and bake if it floats. It works sometimes because gas makes starter buoyant. But it fails in two directions. A thick, stiff starter can float even when past its peak because trapped gas has nowhere to escape. A thin, wet starter can sink even at full strength because it cannot hold a shape. Trust the rise and the timing over the float.

A real scenario

A baker feeds their starter at 8 a.m., sees bubbles by noon, and mixes dough at 6 p.m. thinking later is safer. The loaf bakes flat. The starter had actually peaked at 1 p.m. and been falling for five hours, so by mixing time it was tired. The fix was not more time. It was less: feeding on a schedule, watching for the doubled-and-domed stage around midday, and mixing dough then.

Reviving a sluggish starter

If your starter is slow, thin, or barely rising, it is usually underfed or too cold, not dead. To rebuild strength:

• Feed it a 1:1:1 ratio by weight (equal starter, flour, water) once or twice a day.
• Keep it warm, around 24-26C. Cold kitchens slow everything down.
• Discard down to a small amount before each feed so fresh flour is not overwhelmed by acid.
• Add a spoon of whole wheat or rye, which are packed with the microbes and minerals a culture loves.
• Give it 3 to 5 days of consistent feeding before judging it.

Common mistakes and how to fix them

• Baking on a fixed clock instead of the rise. Kitchen temperature changes the timing daily. Watch the starter, not the hour.
• Trusting the float test alone. Use it as a rough hint at most; rely on doubling and doming.
• Feeding too little flour. A starving culture turns sour and weak. Feed generous fresh flour.
• Keeping it too cold. A chilly counter can make a healthy starter look dead. Find a warmer spot.
• Giving up after two days. A neglected starter often needs several feeds to recover. Be patient.

Action steps

• Mark the jar level at feeding with a rubber band.
• Feed on a schedule and note how many hours to peak.
• Bake when the starter has doubled and is domed or just flattening.
• Judge by rise and smell, not the float test.
• For a weak starter, feed 1:1:1 twice daily in a warm spot for several days.

Conclusion

A ready starter is one caught at the top of its rise: doubled, domed, and tangy. Learn your own starter’s timing curve and mix dough at its peak. Your next step: feed your starter today, mark the jar, and time exactly how long it takes to double. That number is your personal baking window.

FAQ

How long does a starter stay at peak?

Usually one to two hours at room temperature. Warmer kitchens shorten the window; cooler ones lengthen it. Aim to mix dough within that peak.

Can I use starter straight from the fridge?

Not for best results. Cold starter is dormant. Feed it once or twice at room temperature and let it come to peak before baking.

What is discard and do I have to throw it away?

Discard is the portion you remove before feeding to keep acidity in check. You can keep it in the fridge and use it in pancakes, crackers, or waffles instead of tossing it.

My starter has a dark liquid on top. Is it ruined?

No. That liquid, called hooch, means it is hungry. Stir it in or pour it off and feed. Only fuzzy mold or pink or orange streaks mean you should start over.

References

• King Arthur Baking Company, sourdough starter guides
• Chad Robertson, Tartine Bread