A 7–14 day UK-first guide to building a sourdough starter from scratch — British flour brands ranked, UK water hardness map, kitchen-temperature reality, day-by-day schedule with photos, troubleshooting decision tree, four-sign readiness checklist, and what to do with discard.
Mix 50g organic wholemeal or rye flour with 50g room-temperature filtered water in a jam jar. Cover loosely. Repeat once a day for 7–14 days, discarding half each time. When it doubles in 4–8 hours and smells like ripe yogurt, it's ready. UK kitchens in winter sit at 16–18°C — that's the single biggest reason starters stall here. Move it somewhere warmer.
This is the recipe I'd hand a friend who'd just been given a kilo of flour and an empty jam jar. It's the recipe I wish someone had handed me in 2010, when I started my own and killed three before getting one to live. The internet treats sourdough starters like a clergy initiation. They're not. They're a wild fermentation, and once you understand the four things that make one work — flour, water, temperature, and time — they more or less make themselves.
The version below assumes you live in the UK. That matters more than the American guides admit. Our flour brands are different (and largely better). Our kitchens are colder for half the year. Our tap water varies wildly by region. The advice that works in San Francisco doesn't always translate to Frome. So: written from a Somerset kitchen, tested in over a hundred British home kitchens, and not afraid to name brands.
You want the smallest possible kit, not the biggest. You'll use four things: flour, water, a jar, and a kitchen scale. That's it.
The biggest decision you'll make in week one is which flour to feed your starter. The science: you want flour with the most live microflora on it (so wild yeasts and lactobacilli can colonise quickly) and a decent amount of bran or germ (which feeds those microbes). That points firmly at organic stoneground wholemeal or rye for the first 5–7 days, then switching to a lighter mix once the culture is established.
| Flour | Best for | Protein | ~£/1.5kg |
|---|---|---|---|
| Shipton Mill Organic Dark Rye | Days 1–5 (kickstart) | ~12% | £3.20 |
| Marriages Organic Wholemeal | Days 1–7 | ~13% | £2.40 |
| Doves Farm Organic Stoneground Wholemeal | Days 1–7 (widely available) | ~12.5% | £2.10 |
| Wessex Mill Cotswold Crunch | Days 7+ (maintenance) | ~12% | £2.95 |
| Marriages Strong White Bread Flour | Days 7+ (maintenance) | ~13% | £1.95 |
If you can only get one bag, get organic wholemeal — it's available in any UK supermarket and it works. Skip plain flour for starter purposes; you want bread flour or wholemeal. Don't use self-raising; it has chemical leaveners that will mess things up. Don't use bleached flour either — many UK supermarket whites are unbleached, but check the label.
Gluten-free starters work but behave very differently. Brown rice flour, buckwheat, or sorghum will ferment but produce less rise. We don't recommend a gluten-free start for a first-time baker — the feedback signals are subtler.
UK tap water is chlorinated and the levels vary. Chlorine inhibits the wild yeasts you're trying to grow. So:
Don't use distilled or RO water — it's too pure and lacks the trace minerals starters need. Filtered (Brita-style) is the safest middle option.
Three days into your starter build, if you've seen no activity at all and you're in a hard-water region, switch to bottled. Most starter problems blamed on flour are actually water problems. Costs about £1 to test the theory.
You need a 500ml glass jar with a wide mouth (a Le Parfait or Kilner clip-top is ideal — easy to clean, easy to read the rise) and a kitchen scale that measures to 1g. That's it. You do not need:
One thing worth buying: a rubber band, to mark the level of the starter on the side of the jar after each feed. That's the single best progress-tracker we've found.
The honest truth: there's a wide range of "normal" here. Some UK starters are bake-ready by Day 5; others take 14 days. The variable is mostly temperature.
In your jar, mix 50g organic wholemeal or rye flour with 50g room-temperature water. Stir vigorously for 30 seconds — really get air into it. Scrape down the sides. Cover loosely (lid resting on, not screwed shut — it needs to breathe). Mark the level with a rubber band. Leave it somewhere warm.
Where's warm in a UK house? The airing cupboard. On top of the fridge or boiler. In the oven with just the light on (most UK ovens hold around 24°C with the light on alone — perfect). Inside an Instant Pot on the yogurt setting. On a seedling heat mat (£15 from any garden centre, indispensable for winter starters). Avoid radiators (too hot, dries out the surface) and direct sunlight (UV can damage yeast).
Day 2 is dull. That's normal. Welcome to baking. You may see a few small bubbles, you may see nothing. Either is fine.
Discard half (about 50g — bin it; do not tip down the sink, it'll set in your pipes). Add another 50g of flour and 50g of water to what's left. Stir, scrape, cover, mark the new level with the rubber band.
Why bin the discard early on? The microbial community in days 1–4 is dominated by the wrong organisms — bacteria like Leuconostoc that are useful for getting things started but produce off-flavours. From Day 5 onwards, when the wild yeasts and Lactobacillus have established themselves, the discard becomes worth saving.
By Day 3 or 4 you should see real bubbles forming throughout the jar — not just on top. The smell will shift from "wet flour" to something more interesting: a bit cheesy, a bit sour, sometimes faintly like nail-varnish remover. That last one is acetone, a byproduct of early fermentation. It's a sign things are working, not a sign of failure.
Repeat the discard-and-feed routine, same time each day if you can manage it.
Cold kitchen rescue: if by Day 4 you've seen literally no activity, your kitchen is too cold. Move it. The Instant Pot trick is reliable; an electric heating mat sold for seedlings works too. We've had readers raise starters on top of their Sky box.
You should now be seeing the starter roughly double between feeds. The smell will mellow into something pleasant — like ripe yogurt or a glass of cider gone over.
This is when many people switch from wholemeal to a lighter flour. We don't recommend this yet — keep feeding wholemeal or a wholemeal/white blend until Day 7 at minimum. The microbial community is still establishing.
If by Day 6 the starter is bubbling but not rising, the most likely causes are: kitchen too cold, feed ratio too small, or chlorinated water. Switch to a 1:2:2 feed (10g starter + 20g flour + 20g water), move to a warmer spot, and try bottled water for a week.
By Day 7, your starter should pass three of the following four checks. If it does, congratulations — you have a sourdough starter.
The float test (drop a teaspoon of starter into water — if it floats, it's ready) is fine but unreliable. Use these four signs instead.
For the deeper version of this checklist — and why the float test lies — see our guide to when your sourdough starter is actually ready.
Once your starter is established, you have two choices: keep it on the counter and feed it daily, or stash it in the fridge and feed it weekly. The fridge is the answer for most home bakers.
Up to 2 weeks away, fridge it after a feed. It'll be fine. Past 2 weeks, either ask a neighbour to feed it once a week, or freeze a portion as backup (more on that in the FAQ below).
You'll generate ~50g of starter discard a day during the build phase. That's around 350g of flour-and-water by Day 7. Don't bin all of it after Day 5 — the British discard recipes that work even with a young, weak starter:
Our full collection of UK discard recipes covers 25+ ideas.
Most starter problems are one of: too cold, underfed, wrong flour, or chlorinated water. Our deep-dive guide on fixing a sourdough starter that won't rise walks through the seven most common UK problems in priority order.
| Symptom | Most likely cause | Fix |
|---|---|---|
| Bubbles but no rise | Kitchen too cold | Move somewhere warmer (24°C) |
| No bubbles, no smell change | Chlorinated water | Switch to bottled or filtered |
| Smells of nail varnish | Hungry | Feed more often (twice daily) |
| Pink/orange/fuzzy growth | Mould (contamination) | Bin and start over |
| Brown liquid on top | Hooch (hungry) | Stir in or pour off, feed |
Yes. Doves Farm organic wholemeal from any UK supermarket works. Avoid the very cheapest non-organic flour — the bran has often been over-stripped, leaving fewer microbes for fermentation.
That's acetone — a sign your starter is hungry. Feed it more often, or use a higher feeding ratio (1:2:2 or 1:5:5 instead of 1:1:1). It'll mellow out within a day.
Typically 7–14 days. Warmer kitchens (22–26°C) get there in 5–7 days; cooler kitchens (16–18°C, common in UK winter) take 10–14. Move the jar somewhere warmer to speed it up.
Strongly recommended for the first 7 days. Organic stoneground flour has more live microbes on the bran than industrially milled white. After Day 7, you can switch to non-organic strong white if you prefer.
Paul's method uses a 50/50 wholemeal-white mix from Day 1 and a slightly higher hydration. Both methods work. The pure wholemeal start (above) is slightly more forgiving for first-time UK bakers because the bran feeds the microbes harder.
Check the temperature. UK kitchens at 18°C produce bubbles but slow rise. Move it somewhere warmer (24°C) and feed once more — most likely it'll double within 6 hours.
Glass or food-grade plastic only. Metal can react with the acid in the starter and inhibit growth.
For a 500g loaf, you'll typically need 100g of active starter. That means keeping at least 50g going between bakes is plenty.
Yes — you can dry it (spread thin on baking parchment, dehydrate at 30°C for 12 hours, store in a sealed jar) or freeze a small portion in a labelled bag. To revive: rehydrate with equal water and feed daily for 3–5 days.
Pink, orange, or fuzzy growth = mould. Bin it, sterilise the jar, start over. This usually means contamination from a dirty utensil or a really cold spot where wild yeasts couldn't outcompete the mould. Don't try to rescue it.
Yes — that's normal. Cover loosely so air can move; full seal will let pressure build.
Around 50°C. UK kitchens never get that warm — only relevant if you've put it on a radiator.
Clara Ashworth is the founder of The Sourdough Hub. She's been baking sourdough since 2010 and packs every starter kit by hand from her workshop in Frome, Somerset. Her own starter, fed on Marriages organic wholemeal and Frome tap water, has been alive since 2014.
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