If your sourdough starter has stopped rising — or never started — it's almost certainly one of seven things, ranked here by likelihood. UK kitchen temperatures, British flour swaps, hard-water rescue, hooch handling, complete 48-hour rescue protocol, and how to tell the difference between mould, kahm yeast and fruit-fly contamination.
It's almost certainly not dead. It's almost certainly cold. UK kitchens in winter sit at 16–18°C, and a starter that needs 22–24°C to rise won't show much activity at that temperature even with perfect feeds. Move it somewhere warmer for 24 hours, feed it once more, and check.
This is the most common message we get from anyone with a starter, particularly between October and March: my starter has stopped rising. Or it never started rising. Or it bubbles a bit but never doubles. The good news: the diagnosis is almost always one of seven things, and six of them are fixable in 24–48 hours.
This guide walks through them in priority order — the most likely cause first. Try Fix 1 before Fix 2; try Fix 2 before Fix 3. Most starters resolve at Fix 1 or Fix 2.
Probably not. Real starter death is rare. Real signs of an actually-dead starter include:
Anything else — sluggish, hooch on top, smells like nail varnish, hasn't risen for two days — is fixable. Read on.
Before you do anything, run this:
If two of three are fine, your starter is fundamentally OK and just needs better conditions. If all three are alarming, work through the fixes below.
Before working through the seven fixes, run this 60-second check:
That covers ~80% of UK starter problems. If the answers are no, no, decent flour, and decent water — work through the rest of the fixes.
The number one cause of UK starter problems is that the kitchen is too cold. The wild yeasts that drive rise have a strong temperature preference: optimal around 24–28°C, sluggish below 20°C, near-dormant below 16°C.
UK kitchens sit at 16–18°C through autumn and winter for most households. That's enough for some bubbling but not for a proper rise. We've worked with home bakers who'd written off their starters as dead until we suggested moving them to the airing cupboard — and seen those exact starters rise within 12 hours.
Where to put it:
Avoid radiators (too hot, can dry out the surface) and direct sunlight (UV can damage yeast).
A 1:1:1 feeding ratio (1 part starter : 1 part flour : 1 part water) works well for an established mature starter, but a sluggish one often needs more food relative to its existing population.
Try a higher feeding ratio for 3–5 days:
Twice-a-day feeds also help, particularly in a cool kitchen. Morning and evening, same routine. After 3–5 days of bigger or more frequent feeds, most sluggish starters wake up.
A small feed (1:1:1) on a hungry starter just gets consumed in a couple of hours. The starter eats it, doesn't have time to multiply, and is hungry again before you can see results. A bigger feed (1:5:5) gives the existing yeast and bacteria the resources to actually reproduce — to grow the population, not just feed it.
If you've been feeding pure white refined flour, your starter is essentially on a low-microbe diet. Wholegrain flours have far more wild yeasts and bacteria on the bran.
For UK readers, the rescue feed is:
Once the starter is rising consistently again, you can return to your normal flour blend.
Rye flour has the highest enzyme activity of any common bread flour, the highest level of pentosan (a sugar that feeds bacteria), and the most active wild yeast population on its bran. It's why traditional Eastern European bakeries used rye starters even when baking wheat bread.
UK tap water is chlorinated, and the chlorine kills the wild yeasts you're trying to grow. The hardness of the water also matters — South-East England is some of the hardest in Europe (Kent, London, East Anglia at 250+ ppm).
Three options, in order of cost:
If your starter has been on tap water and isn't rising, switch to bottled or filtered for a week and observe.
| Region | Hardness | Action |
|---|---|---|
| Scotland, Wales, Cornwall, Devon | Soft (under 100 ppm) | Tap water usually fine |
| North-West, North-East, Yorkshire | Moderate (100–250 ppm) | Leave overnight or filter |
| South-East, East Anglia, Midlands | Hard (250+ ppm) | Use bottled or filtered for starter |
Hooch is the dark grey or amber liquid that forms on top of a hungry starter. It's a low-alcohol byproduct of fermentation, and it's a sign your starter wants to be fed sooner. It's not a sign of death.
Don't bin a starter with hooch. Either:
Then feed more often. If hooch reforms within 24 hours of a feed, your starter is very active and either needs cooler storage (move to the fridge) or a bigger feed ratio.
If your starter has been fed irregularly — feeds at all hours, missed days, sudden temperature swings — try a strict 5-day reset:
Predictable conditions let the microbial community stabilise. After 5 days of routine, most starters are firing on schedule. The microbial population needs predictability — every change is a stress event for them.
If you've been keeping a tight-lid Kilner jar, your starter may be CO₂-starved. Wild yeasts are aerobic; they need oxygen exchange. Either:
If you've tried the priority fixes and your starter still won't rise, follow this concrete 48-hour rescue plan.
Take 25g of your existing starter. Add 50g of organic wholemeal or rye flour and 50g of de-chlorinated water. Stir vigorously. Mark the level. Place in your warmest spot (24–26°C ideal).
Check rise. If doubled, jump ahead to Hour 24 routine. If not, observe — bubbles? Smell change? Some movement? Note it.
Feed again, same ratio (1:2:2). If you saw no movement at all in the first 12 hours, switch flour to dark rye for this feed.
You should now see clear activity — at minimum bubbles forming, ideally rise. Mark the level.
Final feed of the protocol. By now the starter should be doubling in 6–8 hours at room temperature. If not, repeat the 48-hour cycle once more. If two cycles in, still no rise: it may be time to start a fresh starter (see our UK starter recipe).
Three things often confused for one another — and only one means binning the starter.
Pink, orange, fluorescent green, or fuzzy growth — usually visible on the surface or jar walls. Mycelium spreads invisibly through the starter before visible growth. Bin the whole jar, sterilise with hot soapy water, start fresh.
A thin, pale, slightly creamy film on the surface. Smells slightly off but not putrid. Not harmful but produces off-flavours. Skim off the layer with a spoon, refresh with a 1:5:5 feed, and the kahm yeast usually loses out to the wild yeast within a few days.
Fruit flies in the kitchen, especially in summer, will lay eggs in your starter if the lid is too loose. The result: tiny larvae, eventually visible. Bin the affected starter. To prevent: cover with a tight-weave muslin cloth secured with a rubber band, or move the jar somewhere fruit flies don't roam (a closed cupboard).
Real reasons to bin and start fresh:
Hooch, vinegar smell, slow rise, no rise yet — these are not bin-worthy. Persist.
Once it's working again, set yourself up to keep it that way:
Yeast cells start dying around 50°C. UK kitchens never get that warm — the death-by-cold concern is more relevant in domestic settings.
Almost certainly the kitchen temperature. Move it to a warmer spot (airing cupboard, on the boiler, oven with light on) and observe for 24 hours.
Yes — hooch is a sign your starter is hungry, not dying. Stir it back in or pour off, then feed.
A faint vinegar note at peak is fine. Sharp, eye-watering vinegar suggests the starter is past peak or under-fed. Feed earlier or use a bigger ratio.
On the counter, 2–3 days before it gets very unhappy. In the fridge, 2–3 weeks comfortably; longer with a strong starter, but it'll need a couple of room-temperature feeds to wake.
Either it's not yet mature, the kitchen's too cool, the feed ratio is too small, or it's on the wrong flour. Work through Fixes 1–3 above.
Yes — Tesco/Sainsbury's own-label still mineral water is fine. Avoid distilled.
Probably temperature. Move warmer for 24 hours and observe.
Mild cheese-like smell at peak is fine. Sharp aged cheddar smell or strongly putrid = time for a 1:5:5 reset feed.
Loose. Wild yeasts need oxygen exchange. A tight clip-top will eventually pop from CO₂ pressure.
Clara Ashworth is the founder of The Sourdough Hub. She's troubleshot more failed starters than she can count and runs a small workshop in Frome, Somerset.
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