How to Make a Sourdough Starter from Scratch
A sourdough starter is a live culture of wild yeast and lactic acid bacteria that leavens your bread and creates its distinctive tangy flavour. Making one from scratch takes 7–14 days of once-daily feeding — no special equipment, no commercial yeast, and no prior baking experience required. All you need is flour, water, and a jar.
- A starter is just flour and water. Wild yeast and bacteria naturally present on the flour and in your kitchen colonise the mixture over 7–14 days of consistent feeding.
- Room temperature is the most important variable. Starters ferment much faster at 24°C (75°F) than at 18°C (65°F). A cold kitchen will slow progress significantly.
- Your starter is ready to bake with when it reliably doubles in size within 4–8 hours of feeding and has a domed, bubbly surface at its peak.
- Discard is not waste. Unfed starter makes excellent pancakes, crackers, waffles, and flatbreads. Never throw it away once your culture is active.
- A healthy starter smells pleasantly sour — like yoghurt, beer, or vinegar. Pink, orange, or fuzzy growth means contamination; start over with a clean jar.
What You Need
- Flour: unbleached all-purpose or bread flour to start. Wholemeal or rye flour ferments faster (more wild yeast on the bran) and can be mixed in at 10–20% to speed early establishment. Avoid bleached flour — bleaching agents inhibit fermentation.
- Water: filtered water, or tap water left to sit uncovered for an hour to off-gas chlorine. Heavily chlorinated water inhibits yeast growth.
- A wide-mouth jar: at least 500ml capacity. Use a rubber band or tape mark to track the rise level after each feeding.
- Kitchen scales: measuring by weight is far more accurate than volume. A cheap postal scale works perfectly.
- A loose-fitting cover: the culture needs air circulation. A cloth secured with a rubber band, or a jar lid set on top without sealing, both work.
Day-by-Day Feeding Schedule
Day 1
Combine 50g flour and 50g water in your jar. Stir vigorously for 1–2 minutes to incorporate air. Cover loosely. Leave at room temperature, ideally 21–24°C (70–75°F).
Days 2–3
You may see small bubbles forming and detect a slightly sour or funky smell. The mixture may also smell unpleasant at this stage — that is completely normal. Early fermentation is dominated by less desirable bacteria before the yeast and lactobacillus populations establish.
Feed: discard all but 50g of the starter. Add 50g fresh flour and 50g water. Stir well, cover, leave.
Days 4–7
Activity should increase noticeably. The starter should begin rising and falling in a predictable cycle — domed at its peak, collapsed and bubbly when it falls. The smell should become more pleasant: tangy, yeasty, like beer or yoghurt.
Continue feeding daily at the same time. Same ratio each time: keep 50g, add 50g flour, 50g water.
Days 8–14
A healthy starter will double or more in size within 4–8 hours of feeding, then fall back before the next feed. Once this happens consistently for 3–4 days in a row, the starter is ready to bake with.
How to Tell When It's Ready
The float test: drop a small spoonful of starter into a glass of water at its peak rise. If it floats, the culture has produced enough gas to leaven bread. If it sinks, it needs more time.
The doubling test: mark the level immediately after feeding. If the starter doubles (or more) and has a domed, bubbly surface within 4–8 hours, it is active and ready.
Always use the starter at or near its peak — when it has doubled and the surface is domed. Using collapsed, over-fermented starter produces flat, sour bread.
Troubleshooting
Hooch (grey or dark liquid on top): watery liquid that separates when the starter is hungry and over-fermented. Not harmful — stir it back in or pour it off, then feed. Feed more frequently if this keeps happening.
No activity after a week: check your temperature (cold rooms dramatically slow fermentation), try substituting 10–20g of rye or wholemeal flour in one feeding, and ensure your water is not heavily chlorinated.
Pink, orange, or fuzzy growth: contamination by unwanted mould or bacteria. Discard everything, wash the jar thoroughly with hot water (avoid soap — residue inhibits fermentation), and start over. This is uncommon but it happens.
Very sour but not rising: the bacterial population is established but the yeast hasn't caught up. Keep feeding consistently at room temperature. It usually resolves within a few more days.
What to Do with Discard
Every feeding produces 'discard' — the portion you remove before adding fresh flour and water. This unfed starter is useful, not waste. It works excellently in:
- Pancakes and waffles: sourdough discard pancakes are tangier and lighter than regular ones. No extra rise time required.
- Crackers: mix discard with olive oil, salt, and herbs, roll thin, and bake. Ready in 20 minutes.
- Flatbreads: quick stovetop flatbreads that need no yeast and no rising time.
- Quick breads and muffins: add to any quick bread recipe for tang and to extend shelf life.
Keep a separate discard jar in the fridge and add to it after each feeding. Use within a week.
Keeping Your Starter Long-Term
Once established, a refrigerated starter needs feeding only once a week. Remove it the night before baking, feed it, let it peak at room temperature, use what you need, then refrigerate the rest.
For longer-term storage: spread starter thinly on parchment paper, dry completely at room temperature, crumble into flakes, and store in an airtight container. Rehydrate with equal parts flour and water to revive.
Sourdough baking has one of the most satisfying feedback loops in food hobbies: the starter is alive, it responds to how you treat it, and a well-maintained culture can be kept for decades. Some professional bakeries use starters that are over a century old.
Official Resources
- King Arthur Baking — detailed guides for starter maintenance and first loaves from one of the most trusted baking resources.
- The Sourdough School — in-depth fermentation science and troubleshooting from a specialist sourdough educator.
- Full Proof Baking (YouTube) — methodical, science-focused sourdough instruction with excellent visual demonstrations.
Common questions
- How long does it take to make a sourdough starter?
- Most starters become reliably active within 7–14 days of daily feeding. Cold kitchens (below 18°C / 65°F) slow the process significantly and may take 2–3 weeks. Warmer kitchens (24°C+ / 75°F+) often produce an active starter in 5–7 days.
- Can I use plain flour (all-purpose) or do I need bread flour?
- Both work. All-purpose flour produces a starter that works well for most recipes. Bread flour (higher protein) produces a slightly more active starter and better gluten development. Wholemeal or rye flour ferments faster due to higher wild yeast content on the bran and is useful to add in small amounts during establishment.
- My starter smells like nail polish remover or acetone. Is it ruined?
- No — acetone or alcohol smells indicate an over-fermented or hungry starter. This is the yeast producing ethanol when the available sugars are exhausted. Feed it (discard most of it first), let it recover at room temperature, and feed again in 12 hours. The smell should improve within 1–2 feeding cycles.
- How much starter do I need to keep?
- Most bakers maintain 100–200g of starter. Keeping less (50g) reduces flour waste during maintenance. You can always scale it up before a bake by feeding a larger portion the night before. There's no benefit to maintaining a large quantity if you bake once a week.
- Can I use my starter the same day I feed it?
- Yes — use it at its peak, which is when it has doubled in size and has a domed, bubbly surface. The timing depends on temperature: in a warm kitchen (24°C / 75°F), peak activity arrives in 4–6 hours. In a cooler kitchen (18°C / 65°F), it may take 8–12 hours. Using starter past its peak (when it has collapsed) produces denser, more sour bread.
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