Sourdough Starter Health: How to Read, Fix and Maintain a Strong Starter

A healthy sourdough starter roughly doubles 4–8 hours after feeding at 24–26°C (75–79°F), is domed and bubbly on top, and smells pleasantly tangy — not sharply sour or like nail-polish remover. If yours isn't rising, the usual causes are a cold room, underfeeding, or a young starter — not a dead one. Here's how to read it, fix it, and keep it strong.

Most "starter problems" aren't emergencies. A starter is a living culture of wild yeast and bacteria, and almost everything it does — rising slowly, going liquidy, smelling sharp, forming a dark layer on top — is it telling you something about temperature, feeding, or age. Learn to read those signals and you stop guessing.

From BakeSide's app data. Across the nearly 5,000 sourdough starters BakeSide has tracked, the guidance almost always comes back to the same handful of fixes: get it warmer, feed it more often, and use fresh flour with filtered water. The sections below are built around those levers.

How do I know if my starter is healthy and ready to bake?

A healthy, ready-to-bake starter shows four things together:

• Rise: it roughly doubles in volume after feeding (some strong starters triple).
• Dome: the surface is domed and slightly bubbled at peak, not flat or sunken.
• Bubbles: you can see bubbles throughout the culture, not just a few on top — hold the jar up to the light.
• Aroma: pleasantly tangy and yeasty, a little like plain yogurt or beer. Sharp, acetone-like, or unpleasant smells mean something is off.

The single most useful habit: mark the jar with a rubber band or tape at feeding height, then watch how long it takes to peak. At room temperature (around 24°C / 75°F), a mature starter typically peaks 4–8 hours after feeding. That timing — not any single test — is your best readiness signal.

How long should a starter take to peak?

At ~24°C, expect a peak in 4–8 hours once the starter is mature. Colder kitchens push that to 10–12+ hours; warmer spots speed it up. A brand-new starter (under ~2 weeks old) can be slow and erratic and still be perfectly healthy. What matters is consistency: a starter that doubles in a predictable window, feed after feed, is ready to bake.

What does a healthy starter smell like?

Pleasantly sour, tangy, yeasty — think plain yogurt, ripe fruit, or a splash of beer. As a starter gets hungry between feeds the smell sharpens and can turn briefly acetone-like (that's the "it needs feeding" signal, not spoilage). A foul, rotten, or gym-sock smell, or any visible fuzzy mold, is different — that's the one case to take seriously.

Why is my sourdough starter not rising?

This is the most common worry, and it's almost never a dead starter. Work through the causes in this order — the same sequence BakeSide's photo guidance tends to follow:

1. It's too cold. Yeast activity drops fast below ~21°C (70°F). Fix: move it somewhere warm — 21–26°C (70–79°F). Inside an oven with only the light on, on top of the fridge, or near (not on) a warm appliance all work.
2. It's underfed, or the ratio is too rich to show a rise. Fix: feed on a consistent schedule at a 1:2:2 ratio and give it a warm spot.
3. It's young. Under ~2 weeks, erratic rising is normal. Fix: keep feeding once or twice a day and give it time.
4. The flour or water is holding it back. Fix: use fresh flour (a portion of whole-grain or rye speeds it up) and filtered or dechlorinated water.

If you correct temperature and feeding and still see nothing after a few days, the starter isn't dead — it's dormant, and the revival routine below will bring it back.

Is my starter dead — and how do I revive it?

Genuinely dead starters are rare. A starter can sit neglected in the fridge for weeks — even months — and still come back. It's almost never dead; it's dormant.

How to tell dormant from dead:

• Dormant (revivable): sluggish, little rise, maybe a layer of dark liquid (hooch), sharp smell. This is the normal state of a hungry or cold starter.
• Truly compromised (discard and restart): fuzzy mold (white, pink, green, or black spots) or a genuinely rotten/putrid smell. This is the only common case where you don't try to save it.

The revival routine (3–5 days): pour off any hooch, keep a tablespoon or two of starter, feed at 1:2:2 with fresh flour and filtered water, keep it warm (21–26°C), and feed every 12 hours. Expect little activity on day 1, small bubbles by day 2, a clear rise by days 3–5.

What is hooch, and what does liquid on top mean?

Hooch is the thin layer of liquid — clear, grey, or brown — that forms on a starter. It's alcohol produced by the yeast, and it means one thing: your starter is hungry. It's a feeding signal, not spoilage. Stir it in (more tang) or pour it off (milder) — both are fine. The real fix is to feed more often so it doesn't get so hungry between feeds.

What do sourdough starter feeding ratios mean (1:1:1 vs 1:2:2)?

A feeding ratio is starter : flour : water by weight. "1:2:2" means for every 1 part starter you add 2 parts flour and 2 parts water. More flour and water relative to starter = more food = longer before it peaks and gets hungry.

Feeding ratio	Starter : Flour : Water	Best for	Feed frequency at ~24°C
1:1:1	equal parts	Daily bakers, warm kitchens	Every ~12 hrs
1:2:2	1 part starter, 2 each	Reviving / strengthening a sluggish starter	Every ~12–24 hrs
1:5:5	1 part starter, 5 each	Slowing it down / less frequent feeds	Every ~24 hrs

Weigh with a kitchen scale — cups are unreliable for starter. If your starter peaks and collapses long before the next feed, feed a richer ratio or feed more often.

Do I have to discard, and can I refrigerate my starter?

Discard: yes, when keeping a starter at room temperature and feeding daily, you remove some before each feed so the culture stays well-fed relative to its size. Discard isn't waste — use it in pancakes, crackers, or waffles, or keep a smaller starter.

Fridge: if you don't bake daily, store it in the fridge and feed it once a week. Before you bake, pull it out a day ahead and give it one or two room-temperature feeds to wake it fully. Missed a feed? Don't panic — it just makes your starter hungry (expect hooch and a sharp smell). Resume feeding and it recovers.

Should I trust the float test?

The float test — dropping a spoonful of starter in water to see if it floats — is helpful but not definitive. A starter full of gas floats, which suggests it's active. But a starter can be perfectly ready and still sink, especially wetter or rye-heavy starters. Don't discard a good starter just because it failed the float test. Read the rise, dome, bubbles, and aroma instead.

The bottom line

A strong starter is a habit, not a lucky break: keep it warm, feed it consistently at the right ratio, use fresh flour and filtered water, and learn to read its rise, bubbles, and smell instead of chasing a single test. Almost every problem traces back to one of those levers — and almost none of them mean your starter is dead.

Frequently asked questions

How do I know if my sourdough starter is healthy?

It roughly doubles 4–8 hours after feeding at ~24°C, is domed and bubbly throughout, and smells pleasantly tangy. Mark the jar at feeding height and time how long it takes to peak.

Why is my sourdough starter not rising?

Most often it's too cold, underfed, or too young — not dead. Move it somewhere warm (21–26°C), feed consistently at 1:2:2 with fresh flour and filtered water, and give a young starter time.

How do I know if I killed my starter?

True death is rare. Fuzzy mold or a rotten smell means discard and restart. Sluggishness, hooch, or a sharp smell just means it's dormant or hungry — revive it with warmth and regular feeding.

What is the liquid on top of my starter?

That's hooch — alcohol the yeast produces when hungry. Stir it in or pour it off, and feed more often to prevent it. It's not spoilage.

Does my starter have to pass the float test?

No. The float test is helpful but not definitive — a ready starter can still sink. Judge by rise, bubbles, dome, and aroma instead.

Do I have to discard sourdough starter every time I feed it?

When keeping it at room temperature and feeding daily, yes — or keep a smaller starter. Discard can be used in pancakes, crackers, and waffles rather than thrown away.

About the makers

BakeSide is made by the team behind Superbaking, a community of 500,000+ home bakers. Its starter guidance is grounded in real baking and in the app's proprietary data — thousands of photo analyses, across nearly 5,000 sourdough starters tracked. Every guide here is written from that hands-on experience, human-edited, and fact-checked — never mass-generated.