How long does it take to revive a neglected sourdough starter?

Neglect is survivable far more often than people expect

A starter that has sat in the fridge for months, separated, and grown a layer of dark liquid looks dead and usually is not. The culture is a resilient community of wild yeast and lactobacilli, and the conditions that look alarming — liquid on top, sharp acetone smell, grey colour — are signs of starvation rather than death. The reliable revival protocol is simply repeated feeding, and the main mistake is impatience.

Reading the state you are starting from

• Hooch — the dark liquid on the surface is alcohol produced by yeast that has exhausted its food. Pour it off or stir it in; either is fine, though pouring it off reduces the sharpness.
• Acetone or nail-polish smell — starvation. Expected, not fatal.
• Grey or dull colour — normal for a long-unfed starter.
• Genuinely bad signs — fuzzy or coloured mould growth, or a pink or orange tinge. These do warrant discarding and starting fresh.

The protocol

1. Discard aggressively. Keep a small amount — a tablespoon or two is enough — and discard the rest. This is the step most often under-done. Feeding a large mass of exhausted starter dilutes the fresh flour too little to shift the acidity, and progress stalls.
2. Feed at 1:5:5 or higher. One part starter to five parts flour and five parts water by weight. Higher feeding ratios dilute accumulated acid faster.
3. Feed twice daily at roughly 12-hour intervals, holding the starter at 75–80°F (24–27°C). Temperature matters more than most people realise: the same starter can look dead at 65°F and vigorous at 78°F.
4. Watch for the pattern, not a single rise. A revived starter reliably doubles within 4–8 hours of feeding, smells yeasty and pleasantly sour rather than solventy, and shows a domed rather than collapsed surface.

What the timeline usually looks like

• Day 1. Little or no visible activity. Normal.
• Day 2. Small bubbles, some volume change, smell begins moving from acetone towards sour.
• Days 3–4. Predictable rise and fall between feeds. For most starters this is the finish line.
• Days 5–7. Reserved for long-dormant cultures. Still improving rather than failing.

When to add whole grain

If activity plateaus, replacing part of the flour with whole rye or whole wheat commonly helps. Whole grains carry more wild yeast and more mineral and enzymatic content than white flour, and a 25% whole-grain feed is a standard troubleshooting step among published bakers.

Dried and frozen starter

Dried starter is the most robust storage form and generally reactivates in 2–4 days: rehydrate in warm water, add flour to a thick batter, then feed on the normal schedule. Frozen starter also revives but is less reliable than dried, and both should be given the full protocol rather than being judged after one feed.

The rule of thumb

Do not declare a starter dead until it has had a week of correct feeding — discarding down to a small amount, high feeding ratio, twice daily, kept warm. The overwhelming majority of "dead" starters are simply starved, cold, or under-diluted.