Sourdough Starter 101 — Create and Keep a Living Culture

A sourdough starter is a living culture of wild yeast and lactic-acid bacteria that leavens bread and gives it that signature tang. You can grow one from scratch with nothing but flour and water — or skip the uncertainty and revive a proven heirloom starter.

Two ways to begin

From scratch takes 5–10 days and sometimes stalls. It’s rewarding but unpredictable.

From a dehydrated starter is faster and far more reliable — a known culture wakes up in a few days of feeding. If you want bread sooner rather than later, this is the easier road, and a sourdough starter kit bundles the tools too.

Growing one from scratch

You’ll need flour (whole wheat or rye to start, then bread flour), water, and a jar.

• Day 1: Mix 50 g flour + 50 g lukewarm water in a jar. Cover loosely. Leave at room temperature.
• Days 2–4: Once a day, discard about half and feed it another 50 g flour + 50 g water. You’ll start to see bubbles.
• Days 5–7+: When the starter reliably doubles in size within 4–8 hours of feeding and smells pleasantly sour and yeasty, it’s mature and ready to bake with.

Keeping it alive

• Baking often? Keep it at room temperature and feed once a day.
• Baking occasionally? Store it in the fridge and feed once a week. Pull it out and give it a couple of feedings before you bake.
• The float test: Drop a spoonful in water. If it floats, it’s active and ready to use.

Troubleshooting

• A layer of dark liquid on top (“hooch”) means it’s hungry. Pour it off and feed.
• No activity? It may be too cold. Find a warmer spot (75–80°F is ideal).
• Smells like nail polish remover? Also hunger — feed it more often.

For the science behind why all of this works, Sandor Katz’s The Art of Fermentation is the reference worth owning. Treat your starter well and it can outlive you — bakers pass cultures down for generations.