To make a sourdough starter from scratch, mix 50 g wholemeal flour with 50 ml lukewarm water in a clean jar, leave it loosely covered at room temperature (ideally 20–22°C), and feed it the same way once a day. In around 7 to 14 days it will be bubbly, smell like ripe yoghurt and double in size within four to twelve hours of a feed. That's a bake-ready starter. Here's exactly how we'll get there, day by day.
What You'll Need (And What You Don't)
Before we mix anything, let's lay everything out. A sourdough starter needs four things — flour, water, a jar, and a warm-ish corner of the kitchen. Everything else is optional. No banneton, no fancy proofing box, no specialist sourdough kit (we sell them, but you don't need one for this). Five minutes of setup, then a daily two-minute habit for a week or two.
The flour — why wholemeal or rye to start
The wild yeasts and lactobacilli you need are most abundant on the bran of the grain — the outer husk that gets sifted out of white flour. Wholemeal and rye carry far more bran than strong white, which is why a wholemeal start is almost always faster than a white-only one.
For a UK home kitchen, the brands that work well in our hands and in our customers' jars are Doves Farm Organic Wholemeal Bread Flour, Shipton Mill Light Wholemeal, Marriage's Strong Wholemeal and Bacheldre Stoneground Rye. Our best-start combination is 50/50 wholemeal + rye for the first three days, then a switch to wholemeal alone (or wholemeal taper into strong white) once the starter is moving. Allinson's Strong White will also work all by itself — expect it to add 3 to 5 days. There's a longer comparison if you want it in our rye, white, or wholemeal — which to choose article.
The water — tap is fine, with one caveat
UK tap water is fine almost everywhere. The one caveat: hard-water areas (most of southern and eastern England — check your water board) carry enough dissolved minerals to slow fermentation a touch. Either filter your water, or leave it in an uncovered jug overnight to let any chlorine off-gas. Use it lukewarm — about body temperature, 25–30°C — not hot. Boiling water kills wild yeast. Cold water lets the population stall.
The jar — and why a tall one matters
A clean 500–700 ml glass jar with a loose-fitting lid. A tall narrow jar is better than a short wide one — you'll see the rise more clearly, and you'll have headroom for the inevitable Day 4 double-over-the-top. Mark the starting level with a rubber band, a strip of masking tape or a marker pen on the outside. No screw-tight metal lids; the starter needs to breathe. A square of muslin held with a band, or the lid sitting on top without screwing, is enough.
The kitchen — finding 20°C in a UK home
Most UK homes sit at 16–19°C between October and April unless the heating is on, and 19–23°C from May to September. The Met Office's regional temperature data confirms it — and our own bake logs confirm the kitchen effect of it. Find the warmest stable spot you've got: top of the fridge is often 22°C from the heat exhaust; inside a microwave (off!) with the door closed and a mug of just-boiled water alongside it holds 22–24°C for hours; an airing cupboard, a sunny windowsill in summer. Avoid radiators — over 40°C the yeast dies.
Day 1 — The First Mix
This is the moment. Five minutes of work, then nothing to do for 24 hours. Resist the urge to fuss.
Ratios in grams
Weigh 50 g wholemeal flour (or 25 g wholemeal + 25 g rye) into your jar. Add 50 ml lukewarm water. Stir with a clean fork or spoon until it looks like thick porridge or pancake batter — a few small lumps are fine. Scrape down the sides of the jar so nothing dries to a crust above the line. Mark the level with your rubber band. Cover loosely (muslin held by a rubber band, or the lid balanced on top without screwing). Park it in the warmest stable spot you have.
What a healthy first mix looks like
Beige-brown, dense, smooth-ish. No bubbles yet. It smells like flour porridge — slightly sweet, neutral, faintly nutty if you've used rye. That's it. Nothing else will happen visibly today, and that is exactly correct. Take a photo if you'd like — it makes the journey easier to track later. Set a phone reminder for the same time tomorrow.
Day 2 — Probably Nothing. Don't Panic.
This is the day a lot of people give up. Don't.
The "is it broken?" feeling — read this first
Walk to the jar. Look. There may be a few tiny bubbles on the surface, or none. The mixture looks more or less like yesterday. The smell may be slightly cidery, or still porridgey. This feels wrong. It isn't.
Underneath that lid, billions of lactic acid bacteria are multiplying — they bloom first, before the wild yeasts catch up. You can't see them yet; bacteria don't release the kind of CO₂ gas that yeasts do. The visible rise comes in Days 4 through 7. This is the bacterial-bloom-first, yeast-bloom-second sequence Gänzle & Vogel describe in their lactobacilli review — the bacteria set the pH, the yeast then thrives in the acidic environment, and only then do you see bubbles. Day 2 is when patience is the entire job.
The one thing to do anyway
Add another 50 g wholemeal flour + 50 ml lukewarm water. Stir well. Re-mark the level. Cover. Walk away. Don't discard yet — at this stage we're feeding the population up, not maintaining a steady one. Discarding begins on Day 4 once there's something to maintain.
Day 3 — The First Sign of Life
Somewhere between hour 48 and hour 72, the jar starts to change.
The bubbles you're looking for
What's the first sign a sourdough starter is working?
The first sign a sourdough starter is working is usually a scattering of small bubbles on the surface or down the side of the jar, typically on Day 2 or Day 3. The smell shifts from plain porridge to something slightly cidery or yoghurty. The mixture won't have risen much yet — the visible rise comes later, around Days 4 to 7. Small bubbles, changing smell: that's the heartbeat.
Lift the jar and look at the sides as well as the top. You're looking for pinprick-sized bubbles, scattered, not a uniform foam. They may run up the inside of the glass like champagne. The mixture may have risen a centimetre and then slumped back — that's normal; that's the first ferment-and-fall cycle. Add another 50 g flour + 50 ml water. Stir. Re-mark.
The smell test — yoghurt good, vinegar fine, drains worrying
The smell on Day 3 should be cidery, faintly yoghurty, a touch sweet. Vinegary is also OK — it means the lactic acid bacteria are working hard, which often happens in cool kitchens. What you do not want is rotten, drains, or sulphurous rotten-egg. That suggests contamination or a serious starve — bin it, sterilise the jar with boiling water, start again. Today's feed is the same as yesterday — 50 g flour + 50 ml water. Don't discard yet. Re-mark the level.
Days 4 to 5 — Two Feeds a Day, and the False Peak
This is where the starter really wakes up — and where it might trick you.
Why your starter rises then collapses (and why that's good)
Around Day 4 or 5, you'll likely see the first dramatic rise: the starter doubles, even triples, with a domed top full of holes. Then a few hours later you walk past and… it's collapsed. Flat. Looks dead. This is the false peak. And it's a great sign.
What's happening, in plain terms: the lactic acid bacteria bloomed first and made the jar acidic; the wild yeasts have now caught up and are eating sugars fast, releasing CO₂; once the available food runs out, the gas escapes and the starter's airy structure collapses. The handover from bacterial dominance to yeast dominance. Emily Buehler describes the same arc in Bread Science — pH dropping from about 6.5 down toward 3.5 across the first ten days as the colony settles into its mature ratio of roughly 100 bacteria to 1 yeast cell. From here on, the cycles get more predictable.
Switching to a 1:1:1 feed
Now we start discarding. Twice a day, every 12 hours. Each feed: keep 20 g of the starter (a clean jar each time helps), then add 20 g flour + 20 ml lukewarm water. Stir, re-mark, cover, walk away. Morning and evening works for most people.
Why discard? To keep the food-to-bacteria ratio favourable. Otherwise the population grows beyond what fresh flour can support, the starter goes sour and lethargic, and the rhythm collapses. Don't bin the discard — save it in a jar in the fridge for later. We'll come back to it (it makes pancakes, crackers, crumpets, and a passable pizza dough — there's a whole cluster of discard recipes coming).
Days 6 to 7 — Doubling, Domes, and Champagne
By now, the rhythm is set. Watch what happens after each feed.
The float test (and why we don't quite trust it)
The float test: drop a teaspoon of mature starter into a glass of cool water. If it floats, it's bubbly enough to bake with. Caveat: plenty of perfectly bake-ready starters sink (especially stiffer ones), and plenty of over-fermented starters float (gas trapped from earlier). It's a useful test, not a definitive one. The better signal is predictable doubling in 4 to 8 hours, for two feeds in a row.
What "doubled in volume" actually looks like
Mark the level after each feed. The starter should rise to the top of the jar (or near it) and stay there for an hour or two before slowly subsiding. The three things to look for, together: a domed top with visible bubbles breaking through, bubbles all through the body of the starter (look at the side of the jar, not just the top), and a yoghurty-sweet smell at peak. If you're getting all three, two feeds in a row, you're ready.
Signs Your Starter Is Ready to Bake With
Four signs together. Don't bake on three.
The four-signs checklist
How do I know my sourdough starter is ready to bake with?
A sourdough starter is ready to bake with when it doubles in size within 4 to 8 hours of a feed, smells pleasantly yoghurty (not vinegary, not flat), shows a domed top with visible bubbles through the side of the jar, and a small spoonful floats in a glass of cool water. All four signs together — for two feeds in a row — and you can start your first loaf with confidence.
- Doubles in 4–8 hours after a feed.
- Smells pleasantly yoghurty — sweet-tangy, not vinegary, not flat.
- Domed top, visible bubbles through the side of the jar.
- A teaspoon floats in cool water (with the float-test caveat above).
The peak-time stopwatch
Time the peak. Feed at 8 am, watch when the starter tops out. If it peaks at 12 pm and starts collapsing by 2 pm — that's a 4-hour peak, the strongest signal. If it takes 8 hours to peak, that's still bake-ready. If it takes 12 or more hours, keep feeding for another day or two before deciding it's ready. The peak-time stopwatch is the single most useful diagnostic you'll keep using for years.
Expected daily rise — warm vs cool UK kitchen
How big the rise should be after each feed, by day, in two typical UK kitchens. The dip at Day 4–5 on the warm-kitchen line is the false peak.
Indicative — drawn from The Sourdough Hub's own bake logs and Vanessa Kimbell's published timing tables (S001, S008).
Show the data as a table
| Day | Warm 22°C (rise ×) | Cool 16°C (rise ×) |
|---|---|---|
| 1 | 0 | 0 |
| 2 | 0.1 | 0.0 |
| 3 | 0.3 | 0.1 |
| 4 | 2.5 | 0.5 |
| 5 | 1.5 | 0.8 |
| 6 | 2.0 | 1.0 |
| 7 | 2.5 | 1.2 |
| 8 | 2.7 | 1.5 |
| 9 | 2.8 | 1.7 |
| 10 | 2.8 | 1.9 |
| 11 | 2.8 | 2.1 |
| 12 | 2.8 | 2.3 |
| 13 | 2.8 | 2.5 |
| 14 | 2.8 | 2.6 |
First-Time Pitfalls (And the Gentle Fix)
Almost every UK starter hits one of these. None of them mean failure.
Day 3 panic — when nothing's happening
Why isn't my sourdough starter doing anything on day 3?
A sourdough starter that looks dead on Day 3 is almost always alive and slow, not dead. Three causes cover nearly every case: a cold kitchen (under 18°C), a white-flour-only start instead of wholemeal, or a feed schedule that's drifted. Move the jar somewhere warmer — on top of the fridge, near a radiator (not on it) — and add 10 g of rye to the next feed. Wait 48 hours.
Warmest spot in the house, 10 g rye to the next feed, 48 hours. Almost always fixes it.
The "smelly socks" stage
Around Days 3 to 5 some starters smell genuinely unpleasant — gym socks, mild cheese, a touch of sulphur. This is usually a transient bacterial dominance that passes within 24 to 48 hours as the population rebalances. Keep feeding. If it lasts more than 3 days, or if the smell tips into rotten (not unpleasant — rotten), start again with a clean jar.
A grey or pink layer on top
Grey liquid (hooch) on top — harmless, just hungry; stir it back in or pour it off and feed. Pink, orange, red, or fuzzy growth — that's contamination. Bin the starter, sterilise the jar with boiling water, start again. This is rare in healthy starters because the acidity normally outpaces mould — but it happens, particularly in summer or in jars with food residue.
A 14°C February kitchen — what to do differently
Below 18°C, everything slows. Options, in order of effort: find a warmer spot (top of fridge, oven with the light on but the oven off, a proofing drawer if you have one, the airing cupboard); switch to a higher percentage of rye (rye ferments faster); use slightly warmer feed water (around 30°C); and finally, accept the 12 to 14 day timeline as normal. Don't put the jar on a radiator or in direct summer sun — over 40°C kills the yeast outright.
Smell-and-bubble diagnostic
Pick what your starter smells like and what its bubble pattern looks like. We'll give you a one-line verdict and a next move.
Pick a smell and a bubble pattern above and we'll diagnose.
Your Starter's First Week After "Ready"
You've got a starter. What now?
Bake-keep-or-fridge decision tree
Three options:
- Bake immediately — use the peak starter in a first loaf today. We've written the whole hand-off in the complete UK sourdough starter guide.
- Keep on the counter — daily feeds, bake within a couple of days. Suits people who bake twice a week or more.
- Move to the fridge — feed once a week, take out and warm up for 12 to 24 hours before baking. Suits everyone else, including most of us most of the year.
Most home bakers settle on the fridge rhythm after a week or two. There's a full daily feeding schedule once you're settled.
Linking through to your first loaf
Once the starter is reliably doubling, the next article is the first loaf — we walk through dough timing in UK kitchen temperatures, Dutch oven workarounds, and the gentle, forgiving recipe we use for first bakes. The pillar — the complete UK sourdough starter guide — has the whole map.
Your Day-by-Day Checklist
Tick off each day as you go. Session checklist — refreshing the page resets it.
7-Day Starter Checklist
- Day 1 Done. Onto tomorrow.
- Day 2 If it looks like nothing — that's normal. Read the Day 2 section.
- Day 3 If no — that's still normal. Read the Day 3 section.
- Day 4 Twice a day from here. Don't bin the discard — save it.
- Day 5 Big rise then collapse? That's the bacterial-yeast handover.
- Day 6 Time the peak. That's the signal.
- Day 7 Four signs together for two feeds and you're ready to bake.
0 of 7 days done.
A Note From Clara
Clara always says: "Sourdough is patient on purpose. My first starter took 12 days, not 7 — I'd kept it in a draughty Somerset kitchen and the heating was off. It was fine. It became the mother of every loaf I've baked since."
If your starter is taking longer than this article suggests, it's almost never broken. It's almost always cold. Warm it up, give it another 48 hours, and trust it. We've made hundreds of these. They want to live.
A note on what counts as "true" sourdough. The Real Bread Campaign's Sourdough Loaf Mark defines a genuine sourdough as one leavened solely by a live starter, with no commercial yeast assistance. The starter you're building here is doing all the lifting. That's what you're making. The real thing.
Frequently Asked Questions
How long does a sourdough starter take to make from scratch?
7 to 14 days, with 10 days a fair UK average. Warm kitchens (22°C+) and wholemeal/rye starts land closer to 7; cool British winter kitchens (15–17°C) closer to 12–14. Both are fine.
What's the best flour for starting a UK sourdough starter?
Wholemeal, or a 50/50 mix of wholemeal and rye. Doves Farm Organic Wholemeal, Shipton Mill Light Wholemeal, Marriage's Strong Wholemeal, or Bacheldre Stoneground Rye all work well. Strong white alone works but takes 3–5 days longer.
Can I use UK tap water?
Yes, in most regions. In hard-water areas (most of southern and eastern England — check your water board), either filter or leave the water uncovered overnight to off-gas the chlorine. Use lukewarm — about body temperature.
Why isn't my starter doing anything on Day 3?
Almost always because the kitchen is too cold (under 18°C) or you've used white flour only. Move to a warmer spot (top of fridge, microwave with the door closed and a mug of warm water), add 10 g rye to the next feed, wait 48 hours.
What does a healthy sourdough starter smell like?
Yoghurty and faintly sweet-tangy at peak. Cidery, slightly vinegary, or fruity is also normal. What you don't want is rotten, drains, or strongly sulphurous — that suggests contamination and is rare.
What is the false peak around Day 4 or 5?
A dramatic rise followed by a collapse, caused by the handover between the bacterial bloom (first 3 days) and the wild yeast bloom (Day 4 onward). The yeasts run through the food fast, then the gas escapes. It's a strong sign your starter is alive and developing.
What do I do once my starter is ready to bake with?
Three options: bake immediately, keep on the counter with daily feeds, or move to the fridge with weekly feeds. Most home bakers settle on the fridge rhythm. Take it out and warm it up for 12–24 hours before baking with it.
What's Next
Five companion articles in this cluster, each one a step deeper:
- The full guide — pillar, the long-form version of everything here
- The no-frills recipe-card version — same method, half the words
- How to feed your starter from here — daily and weekly schedules
- Why your starter might still not be bubbling — the long-form troubleshooter
- Rye, white, or wholemeal — which to choose
If you'd rather skip the wait and start baking this weekend, our starter kits ship a mature, named culture from Clara's own jar — already bubbling, already named.
