How to Revive a Neglected Sourdough Starter

A starter forgotten at the back of the fridge rarely dies. It may look gray, smell like nail polish remover and sit under a layer of dark liquid, but the yeast and bacteria in it are usually dormant and hungry rather than gone. What it needs is a clean jar, a small amount of the old culture, and a few days of frequent, warm feedings.

The only reason to throw it out is real spoilage, such as fuzzy mold or pink and orange streaks. Short of that, this guide walks through a reliable revival routine, explains what the smells and liquids mean, and shows how to tell when the starter is strong enough to raise a loaf again.

First, check whether it is safe to save

Open the jar in good light. A dark gray or brown liquid on top, a dry crust on the surface or a sour, alcoholic smell are signs of hunger, not spoilage. Fuzzy patches of any color, or pink, orange or red tints in the starter or liquid, point to mold or unwanted bacteria. In that case, throw out the whole jar, including any surface you might try to scrape away, because mold can grow beyond what you see.

If you are unsure, scoop from the center of the starter. A clean, creamy beige interior under a dry or discolored top is common, and that center is what you will feed.

Dealing with the liquid and crust

The liquid is a mix of water and alcohol produced by starving yeast. Pour it off before feeding for a milder starter, or stir it back in if you like a sharper flavor. Either way, it does no harm. A dried skin on top can be lifted off and discarded.

Do not try to feed the whole jar. Old starter is full of acids and waste, and a large mass dilutes each new feeding. Keeping a small portion and giving it a big meal resets the balance faster.

The revival feeding routine

Wash and dry a jar. Add 25 g of starter from the center of the old jar, then 50 g flour and 50 g water at about 27°C (80°F). Stir until no dry flour remains, scrape down the sides and put a loose lid or cloth on top. Mark the level with a rubber band or tape.

Every 12 hours, discard all but 25 g and feed again with 50 g flour and 50 g water. For the first two or three feedings, use a portion of whole wheat or rye flour, about a quarter of the total, because whole grains carry extra nutrients that wake microbes up quickly. Then return to your usual flour.

• Feeding ratio: 1 part starter, 2 parts flour, 2 parts water by weight
• Timing: every 12 hours at 24 to 27°C (75 to 80°F)
• Water: filtered or tap water left uncovered for a few hours if it is heavily chlorinated

Finding a warm spot

Temperature affects revival speed more than almost anything else. At a cool 18 to 20°C (64 to 68°F), recovery can take a week. Place the jar in an oven with only the light on and the door cracked, on top of the fridge, or near but not on a warm appliance. Check the temperature with a thermometer; an oven light can push the inside above 32°C (90°F), which stresses the culture.

A warm water bath works too: set the jar in a bowl of water at about 27°C (80°F) and top it up with warm water when it cools.

Reading the smell and rise

Expect the first day or two to be sluggish. The starter may bubble a little and rise slightly, then stall. A sharp acetone smell is normal at this stage and fades as feeding becomes regular. By day two or three, most starters begin to rise noticeably within 6 to 8 hours after feeding.

Look for consistency rather than a single dramatic rise. A starter that doubles once and then barely moves the next time is not ready. When it climbs to at least double its marked level, domes on top, then slowly falls, at roughly the same times each cycle, the yeast population has recovered.

Baking with a revived starter

Give it one extra day of steady feedings after it first looks lively, then use it at its peak, when it is domed and full of bubbles. Bread made right after revival can taste a bit more sour and rise a little more slowly; that fades within a week of regular use.

If you go back to refrigerator storage, feed it, let it sit at room temperature for an hour or two until it just starts to bubble, and then chill it. Set a weekly reminder to feed it, or switch to a stiffer starter that tolerates longer gaps.

Common questions

How long can a starter sit in the fridge and still be revived?

Many starters recover after two or three months of neglect, and some after longer. The more time that has passed, the more feedings it may need. As long as there is no mold or pink or orange discoloration, it is worth trying.

My starter smells like nail polish remover. Is it ruined?

No. That smell comes from by-products of hungry yeast. It fades once you return to regular feedings at a warm temperature, usually within a day or two.

Why isn't my revived starter rising after three days?

The usual causes are a cool room, chlorinated water or flour that lacks nutrients. Move it somewhere around 26°C (79°F), add some whole wheat or rye flour and keep feeding every 12 hours. Some starters need up to a week.