A sourdough starter that's not bubbling almost always traces back to one of three things: temperature, feed schedule, or flour. The good news — you almost certainly haven't killed it. Starters are tougher than the panic suggests. This guide walks through the ten most common reasons a UK starter goes quiet, with a fix for each, and a smell-test you can do right now to narrow it down before you change anything else.
Before You Change Anything — The Five-Second Smell Test
Why does my sourdough starter not bubble up?
A sourdough starter doesn't bubble for one of three reasons: it's too cold, it's underfed, or the wild yeast colony hasn't built up yet. Sniff the jar first. Yoghurty and mildly sweet = healthy, just slow. Sharp vinegar = past peak, feed it. Acetone or nail-varnish = starving, feed it now. Off or musty = bin it and start again. The smell tells you which fix to try before you change anything else.
Most bakers panic and change three things at once — move the jar, switch flour, double the feed. Then they can't tell what worked. Our approach is the opposite: smell first, then look, then change one variable. Open the jar. Don't stir. Take a slow breath in through the nose. You'll know within 24 hours whether the fix worked.
Use the Decision Tree
If you'd rather not read all ten reasons, click through the questions below and the tree will route you to the most likely cause. Each leaf links to the relevant section on this page.
Symptom-to-Diagnosis Tree
1. Your Starter Is Still Too Young
What to look for
New starters (under 14 days) often look completely dead between days 3 and 7. This is the false-rise phase — the leuconostoc bacteria that bubbled in the first 48 hours have died off, and the lactobacilli and wild yeasts haven't taken over yet. The jar looks flat, smells faintly cabbage-y, and a watery layer may appear.
The fix
Keep feeding once a day at 22 °C. Don't change the flour, don't change the ratio. Patience is the medicine. By day 8–10, the bubbles return — usually with a vengeance. If you want the full timeline, how long a new starter actually takes covers it in detail. The species-succession (leuconostoc → lactobacilli + yeast) is well documented in Gänzle & Vogel's lactobacilli reviews — there is nothing wrong with your starter.
2. Your Kitchen Is Too Cold
What to look for
A starter at 14–17 °C looks asleep. It might bubble at 30+ hours after a feed instead of 6–12. Press the back of your hand to the jar — if it feels cool to the touch, the starter is colder than 20 °C. UK kitchens in winter are much colder than the US bloggers' kitchens. The Met Office monthly mean for Bristol is around 4 °C in February; an unheated UK kitchen sits at 14–16 °C through January and February. That is the default, not the edge case.
The fix
How do I get my sourdough starter to be more bubbly?
To make a sourdough starter more bubbly, raise the temperature and switch in 25% wholemeal rye flour. The yeast and lactobacilli double in activity for every 8–10 °C rise inside the realistic kitchen range (14–24 °C). Place the jar in the oven with only the light on (it sits around 26 °C), or in a bowl of 30 °C water, or near a boiler. Feed once a day and watch peak time roughly halve.
Three specific UK options that work: (1) oven with the light on (sits 24–28 °C, check with a thermometer first); (2) airing cupboard near the hot-water tank (often 26–30 °C — perfect); (3) a bowl of 30 °C tap water with the starter jar sitting in it, refreshed twice a day. Avoid: radiators (too hot, too uneven), windowsills (cold draughts), top of the fridge (only warm if you cook a lot). Above 37 °C, yeast activity drops; above 50 °C it dies — so no putting the jar on the boiler itself.
3. You're Feeding It Too Rarely (Or Too Much at Once)
What to look for
A hungry starter will show clear or brown hooch (the liquid that separates) within 24 hours of a feed. The jar smells sharp — vinegar territory rather than yoghurt. Bubbles may have happened and collapsed.
The fix
Twice-a-day feeds for three days, 1:1:1 ratio by weight (20 g starter + 20 g flour + 20 g water is plenty). The full feeding ratios in detail piece covers the maths. Avoid the trap of "I'll just give it a giant feed to make up for it" — that's actually covered in Reason 7. Elaine Boddy's small-starter framework holds here: most UK home bakers keep the jar too big, then under-feed it relative to the jar's volume.
4. You're Feeding It Too Often
What to look for
What are the signs of an overfed sourdough starter?
An overfed sourdough starter is sluggish, watery, and never quite peaks. The jar looks loose and pale, with only a few bubbles around the edge. You may see a thin layer of clear or grey liquid sitting on top (hooch) within 12 hours of a feed — that's the starter telling you it's exhausted, not hungry. Overfeeding dilutes the yeast colony faster than it can rebuild. Slow down.
The fix
How do you revive a sluggish sourdough starter?
Revive a sluggish sourdough starter with three days of patient feeding in a warmer spot. Discard down to 20 g of starter. Feed 20 g flour and 20 g water — a 1:1:1 ratio — twice a day, at roughly 12-hour intervals. Keep the jar at 22–24 °C: an oven with the light on works, or near (not on) the boiler. By day three, it should be doubling within 6–8 hours.
This is the most counter-intuitive cause. New bakers, primed by every YouTube video to "feed it twice a day no matter what," will feed before the starter has actually peaked from the previous feed. Result: the yeast colony never gets to multiply because it's drowned in fresh flour. The fix is patience plus one feed per day until the starter shows it can double in 8–12 hours.
5. The Flour Is the Problem
What to look for
Strong white starters are slow. Sluggish-but-not-sick starters fed only on strong white in a cool UK kitchen can take 18+ hours to peak. Bleached flour (rare in the UK but not impossible — check the bag) actively suppresses yeast. Plain (cake) flour is too low in protein to feed a starter well.
The fix
Swap in 25% wholemeal rye for one feed. Most UK supermarkets carry Doves Farm or Bacheldre rye. Within 12 hours, the bubbles return. After that you can return to white if you prefer. The flour-type behaviour breaks down like this: wholemeal rye is fastest (6–8 h peak at 22 °C), wholemeal wheat next (8–12 h), strong white slowest (12–16 h), spelt around 10–14 h. Rye carries more Lactobacillus sanfranciscensis — the species that drives most of the bubble production in mature starters.
6. Your Tap Water Is Working Against You
What to look for
Two flavours of water trouble. (a) Heavily chlorinated water suppresses yeast — common in summer in some UK regions where water boards increase chlorination. Tell-tale sign: starter was fine, then went quiet for a week with no other change. (b) Very hard water (300+ mg/l CaCO₃) can over-buffer the pH and slow lactobacilli. Tell-tale sign: very hard-water areas (much of southeast England, parts of the East Midlands) consistently report slower starters than soft-water areas.
The fix
For chlorine: leave a jug of tap water uncovered overnight — chlorine evaporates. Or filter through any standard Brita-type filter. For very hard water: use 50/50 tap and filtered water for feeds. The Sourdough Hub's own kitchen is in Somerset (Wessex Water, ~280 mg/l — moderately hard) and we use a mix.
| Region (water board) | Hardness (mg/l CaCO₃) | Classification | Starter effect |
|---|---|---|---|
| Scottish Water | 30 | Very soft | Excellent |
| Northumbrian Water | 80 | Soft | Excellent |
| United Utilities (NW) | 100 | Moderately soft | Good |
| Welsh Water | 110 | Moderately soft | Good |
| Yorkshire Water | 150 | Slightly hard | Good |
| Severn Trent | 200 | Moderately hard | Watch for winter slowness |
| Wessex Water (Somerset — the Hub) | 280 | Hard | Mix with filtered water |
| Thames Water | 290 | Hard | Mix with filtered water |
| Anglian Water | 350 | Very hard | Filter or 50/50 bottled |
| Affinity (Herts/Beds) | 360 | Very hard | Filter or 50/50 bottled |
7. The Ratio Is Off
What to look for
Volume measurements ("a cup of flour, a cup of water, a spoon of starter") are wildly inaccurate. A US cup of UK strong flour weighs around 140 g; a US cup of water weighs 237 g. That's a 60% hydration mismatch before you've started. Result: too-stiff starters that look dead because they physically can't bubble through the dough.
The fix
Weigh everything. Equal weights of flour, water, and existing starter — the 1:1:1 ratio. A £8 set of digital scales sorts it for life. If your starter has been on volume measures for weeks, switch and give it three days before judging.
8. It Bubbled, Peaked, and Fell — and You Missed It
What to look for
Why has my sourdough starter stopped bubbling after a few days?
A sourdough starter that bubbled for the first few days and then stopped is almost always going through the false-rise phase. Around days 3–5, the leuconostoc bacteria that caused the early bubbling die off, and the lactobacilli and wild yeasts that will actually leaven your bread haven't taken over yet. The starter looks dead. It isn't. Keep feeding once a day for another four to six days and it returns.
The other version: an elastic band around the jar at the post-feed level. If the band ends up above the current starter line, the starter rose and fell. You missed peak.
The fix
Watch for the rise over the next feed cycle. At 22 °C, a healthy mature starter peaks 6–8 hours after a 1:1:1 feed. Cooler kitchens, longer. The decay chart below shows the curve for three temperatures — use it to predict when to bake or refresh.
9. It's Been in the Fridge Too Long
What to look for
Fridge-stored starters go dormant. After 3–4 weeks unfed in the fridge, the surface develops brown or grey hooch, the jar feels lifeless, and the smell is sharp (acetic acid from anaerobic fermentation). This is dormant, not dead.
The fix
Bring it to room temperature for two hours. Pour off the hooch (don't stir it in — too acidic). Feed 1:1:1 in a clean jar. Repeat twice a day for 2–3 days at 22 °C. Most starters revive completely in 48–72 hours. For starters that have been forgotten 3+ months, the full reviving a dormant starter from the fridge walk-through covers the dried-on-the-jar trick.
10. It's Contaminated (or You Think It Is)
What to look for
Bin-it signs: visible pink, orange, fuzzy, or coloured mould (white spots that look like flour spots are usually fine — mould is fuzzy and has structure). Smell of wet paint, bins, vomit, nail varnish (acetone — actually fixable, see Reason 4), or pure rot. A pink or orange streak through the body of the starter — that's the bacterium Serratia, bin immediately.
The fix
Almost never a fix — these are start-over signs. Wash the jar with hot water and washing-up liquid (no need to sterilise — just clean), and start a fresh 50 g flour + 50 g water mixture. Or order a fresh starter kit. Both work. We discuss the choice in the "When to start over" section below.
The Smell-to-Diagnosis Matrix
Smell is the fastest and most accurate diagnostic a home baker has. The aroma compounds in a starter map to specific chemistry — ethyl acetate (nail-varnish smell) signals yeast starvation; acetic acid (vinegar) signals past-peak; lactic acid (yoghurt) signals healthy peak. Buehler's Bread Science (Chapter 5) maps these compounds in detail; you can use them as your live diagnostic.
Yoghurty, mildly sweet, faintly fruityHealthy peak — your starter is ready or about to be.
Bake within 4 hours, or feed and refrigerate.
Sharp vinegarPast peak, hungry — fermentation has run out of food.
Feed 1:1:1 now; bake from the next peak. Reason 3 →
Acetone / nail-varnish / pear-dropsStarving — yeast switched to alternative fermentation pathway.
Feed immediately, then twice a day for 2 days. Reason 4 →
Cabbagey / lightly sulphurousFalse-rise phase — new starters, days 3–5.
Keep feeding, do nothing else. Reason 1 →
Beery / boozy / alcohol-heavyVery over-ripe; thick brown hooch likely.
Pour off hooch, feed 1:1:1, repeat 24 h later. Reason 9 →
Wet paint / mouldy / offContaminated.
Bin and rebuild — see "When to Start Over". Reason 10 →
Faint, almost nothingCold.
Move to a 22 °C+ spot for 24 h. Reason 2 →
How Activity Decays Between Feeds
Activity as a percentage of peak rise, plotted against hours since feed, at three temperatures — 18 °C (a typical UK winter kitchen), 22 °C (a heated UK kitchen), 26 °C (oven-light or airing cupboard). Source: The Sourdough Hub's own Somerset bake logs. The chart shows visually why a "dead" starter at 18 °C is usually just slow. Peak at 18 °C is around hour 14; you have to wait.
Peak time roughly halves for every 4 °C rise inside the realistic UK kitchen range.
Show the data as a table
| Hours | 18°C (% of peak) | 22°C (% of peak) | 26°C (% of peak) |
|---|---|---|---|
| 0 | 0 | 0 | 0 |
| 4 | 15 | 40 | 75 |
| 6 | 30 | 65 | 100 |
| 8 | 50 | 100 | 85 |
| 10 | 75 | 90 | 60 |
| 14 | 100 | 70 | 40 |
| 18 | 85 | 55 | 30 |
| 24 | 60 | 40 | 20 |
| 30 | 45 | 30 | 15 |
| 36 | 35 | 25 | 10 |
When to Start Over
Honest, gentle. Three categories:
- Keep feeding. For anything in Reasons 1–9, given 3–5 days of consistent care, a starter will recover.
- Bin and rebuild. For visible mould, off smells, or starters older than 4 weeks that have already been on twice-daily feeds with no response.
- Order a fresh kit. For anyone who has had two failed builds in a row and would rather start with a mature, already-active culture so the first month is about learning to bake, not learning to nurture a culture.
If category 3 sounds like where you've landed, our Express Kit (£24.99) is the realistic option — a kit with a ready-made starter, instructions, and a jar. No pressure: a tablespoon of supermarket wholemeal rye and seven days of feeding will get you there just as well.
Clara's "Gerald" story: one winter a customer in Edinburgh — Sarah K — emailed us about a starter she'd named Gerald that had gone silent on day 6. She'd been about to bin it. We told her to move it to the airing cupboard, switch one feed to rye, and wait. Day 9, Gerald rose like a soufflé. He's still going. The lesson Sarah taught us: starters don't really die. They sulk. And UK kitchens make them sulk for longer than the bloggers admit.
Frequently Asked Questions
How long should I wait before deciding my sourdough starter is dead?
At least seven days of consistent twice-daily feeding at 22 °C before concluding a starter is dead. Most "dead" starters revive within 72 hours of warm, consistent feeds. True death is rare — visible coloured mould, an unmistakable wet-paint or bin smell, or having been heated above 50 °C are the only certain signs. Otherwise: feed it and wait.
Is my sourdough starter dead?
A sourdough starter is almost never dead — even ones forgotten for months usually revive with a week of consistent feeding. It's only truly dead if it has visible pink, orange, or fuzzy mould; smells of wet paint, vomit, or bins; or has been heated above 50 °C. Hooch, vinegar smell, grey water and inactivity are all fixable. When in doubt: feed it twice a day for three days at 22 °C and reassess.
Why is my sourdough starter watery on top?
The watery layer is hooch — a mixture of water and alcohol that separates when the starter is hungry or has been left too long. Clear, grey or brown hooch is harmless; pour it off and feed the starter 1:1:1. Pink or orange streaks are a sign of bacterial contamination; bin the starter and start again.
Why does my starter smell like nail-varnish remover?
Acetone or pear-drop smells mean the yeast has switched to an alternative fermentation pathway because it's run out of sugar. The starter isn't dead — it's starving. Feed it immediately at a 1:1:1 ratio and again 12 hours later. By the second feed, the smell should shift back toward yoghurt or vinegar.
Can I bake with a sluggish starter, or do I need to wait?
Wait until it can double within 8 hours of a feed at room temperature — that's the threshold for reliable leavening. Baking with a sluggish starter produces dense, gummy loaves that won't rise properly. Three days of warm, consistent feeding usually gets a sluggish starter back to bake-ready.
How warm should my kitchen be for sourdough starter?
22 °C is ideal; 18–24 °C is the workable range; below 18 °C, fermentation slows noticeably. UK kitchens often run at 14–17 °C in winter, which is workable but slow — you'll wait 18–36 hours between feeds instead of 8–12. An oven with the light on, an airing cupboard, or a bowl of warm water around the jar all work.
Does it matter what flour I use to feed my starter?
Yes — wholemeal rye is fastest, wholemeal wheat next, strong white slowest. Bleached flour suppresses yeast and should be avoided. Plain (cake) flour is too low in protein. If your starter is sluggish on strong white, swap in 25% wholemeal rye for one feed; activity usually returns within 12 hours.
Should I start over or keep trying to fix my starter?
Keep trying if it has any bubbles, any smell other than off/rotten, and no visible mould — three days of warm, consistent feeding fixes most cases. Start over if you see pink, orange or fuzzy mould; if it smells of wet paint, bins or vomit; or if two consecutive weeks of warm twice-daily feeds have produced no response.
What's next
If you fixed it: take a photo at peak, mark the jar with a rubber band, and write down what time you fed it. Patterns matter. If you didn't fix it: rerun the smell test in 24 hours after the next feed — most stuck starters change within one cycle. The full complete UK guide to sourdough starters ties everything together. For a plain-English refresher on what a starter actually is, in plain English, that piece is the gentler entry-point.
