Reviving a neglected sourdough starter

The signs of life

It is incredibly common to find a jar of starter that has been pushed to the back of the refrigerator and forgotten for several months. Often, a dark, watery layer of liquid — known as hooch — will have accumulated on top, and the mixture may emit a strong aroma resembling vinegar, nail polish remover, or heavy acetone. While this appearance can be highly discouraging, the wild yeast and lactic acid bacteria within the mixture are usually just dormant rather than dead. These microscopic organisms are incredibly resilient and can survive for surprisingly long periods without fresh food, waiting patiently for the right conditions to return.

To begin the revival process, you can either stir the dark liquid back into the mixture or pour it off. Pouring it off is generally preferred if the culture has been neglected for more than six months, as it helps reduce the overall acidity of the remaining paste. Measure out a tiny portion of the sludge — about 15 grams is more than enough — and transfer it into a clean, dry glass jar. “It smells like paint thinner,” my neighbor once told me when reviving hers, but this is simply a natural byproduct of prolonged starvation rather than a sign of permanent spoilage.

The first feeding

Provide this small portion with 30 grams of unbleached flour and 30 grams of lukewarm water, aiming for a temperature around 70 degrees Fahrenheit. When choosing your flour, keep in mind how different grains affect the fermentation rate and how flour protein content dictates how well the mixture holds onto the gas bubbles produced by the reviving microbes. Stir the mixture vigorously with a clean spoon or spatula to incorporate plenty of oxygen, which encourages the yeast cells to reproduce after their long period of inactivity. Scrape down the sides of the jar so you can clearly see any future rise.

Set the jar in a warm spot, ideally between 72 and 78 degrees Fahrenheit. If your kitchen is cool, placing the jar on top of a refrigerator or inside an unlit oven with the light turned on can provide a gentle source of heat. Do not expect to see immediate activity or a rapid rise in the jar. The first 24 hours are primarily about hydration and waking up the sluggish cells. You might only see a few tiny bubbles on the surface by the end of the day, but this is progress… we just need to be patient and let the biology work.

Establishing the routine

After the initial 24 hours, discard all but 15 grams of the mixture and repeat the feeding with another 30 grams of flour and 30 grams of water. By the third day of this consistent routine, you should notice a sweeter, more yeasty aroma replacing the harsh acidic smell. The mixture should begin to show visible signs of life, with bubbles scattered throughout and a slight increase in volume. This daily cycle of discarding and feeding helps lower the acidity of the environment, making it hospitable for the yeast to thrive once again. You will know you are successful when the mixture starts to rise predictably after every single feeding.

Once the mixture consistently doubles in volume within four to six hours after a feeding, it is fully active and ready to be used in your baking. Keeping your culture healthy does not require daily attention unless you bake every day. A weekly feeding followed by storage in the refrigerator is enough to keep it in prime condition. Having a robust culture ready in your kitchen means you can easily adapt to different recipes, whether you are managing the complexities of reducing yeast at altitude or preparing a standard loaf for Dutch oven baking on a quiet Sunday morning.