How to Make and Maintain a Sourdough Starter

Your Living Culture

A sourdough starter is a mixture of flour and water that has been colonised by wild yeast and bacteria. Once established, it can be maintained for years — even decades — with regular feeding. Some bakeries work with starters that are over a century old.

It's the engine of every real sourdough loaf: the wild yeasts leaven the bread, while the Lactobacillus bacteria produce the acids that give sourdough its flavour and keeping quality. Build one well and it will outlast every packet of commercial yeast you'd otherwise buy. For the bigger picture on why sourdough is worth it, see Sourdough: The Ancient Art of Real Bread.

How to Create a Starter from Scratch

Picture this: a glass jar on a kitchen counter, bubbling away like a tiny science experiment. That's all a starter is — and it's about to become the most demanding pet you've ever owned. (It eats daily, smells questionable, and will guilt-trip you if you neglect it.)

You'll need:

• Unbleached flour (wholemeal or rye works best for starting, as they contain more wild microorganisms)
• Water (filtered or left to stand if your tap water is heavily chlorinated — chlorine can inhibit bacterial growth)
• A clean glass jar
• Patience (about 5–7 days)

Day 1: Mix 50g flour and 50g lukewarm water in your jar. Stir well, cover loosely (a cloth or loose lid — it needs to breathe), and leave at room temperature (ideally 20–25°C).

Day 2: You may see a few bubbles. Discard half the mixture, then add 50g flour and 50g water. Stir, cover, and leave.

Days 3–4: Activity should increase — more bubbles, a slightly tangy smell. Continue the daily routine: discard half, feed with 50g flour and 50g water.

Days 5–7: Your starter should be reliably doubling in size within 4–8 hours of feeding, with a pleasant sour smell and lots of bubbles throughout. It's ready to bake with.

If nothing happens after 7 days: Try switching to rye flour (more microbial activity), moving it to a warmer spot, or using filtered water. Don't give up — some starters are slow to establish. They're like sourdough teenagers: unresponsive at first, but they get there.

Maintaining Your Starter

Once established, a starter is remarkably resilient:

• If baking regularly (weekly or more): Keep it at room temperature and feed it daily — discard half, add equal parts flour and water.
• If baking less often: Store it in the fridge. Feed it once a week. Take it out and feed it 1–2 times the day before you want to bake.
• Going on holiday? Feed your starter, then put it straight in the fridge. It can survive 2–3 weeks without feeding. Some bakers have revived starters after months.
• Backup: Spread a thin layer of active starter on baking paper and let it dry completely. Crumble it up and store it in an airtight container. This dried starter can be reactivated months or even years later by mixing it with flour and water and resuming daily feeds.

Troubleshooting Your Starter

• Nothing's happening. Slow starts are normal, especially in a cool kitchen. Switch to rye flour, find a warmer spot (an oven with just the light on works well), and make sure your water isn't heavily chlorinated.
• Is it ready? Use the float test: drop a teaspoon of starter into water. If it floats, it's aerated enough to bake with.
• A dark liquid on top ("hooch") is normal — it's just alcohol from fermentation, and a sign your starter is hungry. Stir it back in or pour it off, then feed.
• Pink, orange, or black patches, or a putrid (rather than sour) smell mean something has gone wrong. Discard it and start again.
• Hygiene matters. Use clean jars and utensils. A healthy, acidic starter is largely self-protecting, but dirty equipment can introduce unwanted organisms before the culture is established.

Once your starter is bubbly and reliably doubling, you're ready for the main event: How to Bake a Sourdough Loaf.