What Is a Sourdough Starter?
A sourdough starter is a fermented mixture of flour and water that captures wild yeast and beneficial bacteria from the environment. These microorganisms produce carbon dioxide (which makes bread rise) and lactic acid (which gives sourdough its tangy flavour). Unlike commercial yeast, a sourdough starter is a living culture that you maintain by feeding it regularly.
Creating one from scratch takes about 7 days, and once established, a well-maintained starter can last decades — or even be passed down through generations. Some famous bakeries use starters that are over 100 years old.
What You'll Need
- A clean glass jar — at least 500ml capacity. Wide mouth is ideal.
- Whole wheat flour or rye flour — for the first few days (more nutrients attract wild yeast faster).
- All-purpose flour — for regular feeding once the starter is active.
- Filtered or bottled water — chlorinated tap water can inhibit yeast growth. If you must use tap water, let it sit uncovered overnight to off-gas chlorine.
- A kitchen scale — accuracy matters when feeding.
- A rubber band or marker — to mark the level after feeding so you can measure rise.
Day-by-Day Schedule
Day 1 — The Beginning
Combine 50g whole wheat flour and 50g warm water (about 28°C) in your jar. Stir vigorously for 30 seconds to incorporate air. Cover loosely with a lid or cloth secured by a rubber band — you want air exchange but not insects. Place in a warm spot (24–28°C is ideal). Mark the level with a rubber band.
Day 2 — Wait & Watch
You may see nothing happening, or you may see small bubbles. Both are normal. Do nothing today — just leave the jar alone. The initial bacterial colonisation needs time. If you see a dark liquid forming on top, that's called "hooch" — it's harmless alcohol produced by hungry bacteria. Just stir it back in.
Day 3 — First Feeding
Discard half the starter (about 50g) and feed with 50g whole wheat flour + 50g water. Stir well. The discard is important — it keeps the acidity in balance and gives the fresh flour room to ferment. You might see more bubbles now. The smell might be quite pungent — almost cheesy or vinegary. This is normal and temporary.
Day 4 — Bubbles Appear
Repeat: discard half, feed with 50g flour + 50g water. You can switch to all-purpose flour from today onwards, or continue with whole wheat. The starter should be showing consistent bubbles. Mark the level after feeding and check in 8–12 hours to see how much it has risen.
Day 5 — Getting Active
Same routine: discard and feed. By now, the starter should be rising noticeably — perhaps 25–50% of its volume. The smell should be transitioning from harsh and vinegary to a pleasant, mildly tangy aroma. If it's still sluggish, try placing it in a warmer spot. Temperature is the single biggest factor in starter activity.
Day 6 — Almost There
Discard and feed. Now feed twice today — once in the morning and once in the evening (12 hours apart). This accelerates the yeast population. The starter should be doubling in volume within 6–8 hours of each feeding. You'll see a domed top and lots of bubbles when you look through the glass.
Day 7 — The Float Test
Feed the starter. When it has doubled (typically 4–6 hours later), perform the float test: drop a small spoonful into a glass of water. If it floats, your starter is ready to leaven bread! If it sinks, keep feeding twice daily for another 1–2 days. Some starters take up to 14 days — patience is key.
Ongoing Maintenance
- Daily use: Keep at room temperature, feed once or twice daily with equal parts flour and water.
- Weekly use: Store in the fridge. Feed once a week (discard, add flour and water, let sit for 1 hour, then refrigerate).
- Before baking: Take the starter out 24 hours before you need it. Feed it 2–3 times to "wake it up" and get it at peak activity.
Troubleshooting
- No activity after 5 days — move to a warmer spot, try whole rye flour, or add a tiny pinch of sugar.
- Pink or orange mould — discard everything and start over. This means harmful bacteria have colonised.
- Strong alcohol/vinegar smell — the starter is hungry. Feed more frequently or with more flour.
- Rises then falls quickly — you're catching the "false rise" from leuconostoc bacteria. Keep feeding — the real yeast will take over by day 5–6.
- Very liquid consistency — reduce water slightly, or switch to bread flour which absorbs more.
Name Your Starter
It's a tradition among bakers to name their starters. Some famous ones include "Clint Yeastwood," "Bread Pitt," and "Dough Corleone." Naming your starter makes you more bonded to it — and more likely to remember to feed it. After all, you're now responsible for a living organism that will help you bake incredible bread for years to come.