Six likely causes of dense sourdough — under-proofing, weak starter, low hydration, poor shaping, oven temp, scoring — with crumb-photo diagnostics, UK fan-oven temperatures, British flour-specific hydration tables, and a 24-hour rescue plan if you've already mixed.
Dense sourdough almost always comes down to one of three things: a starter that wasn't strong enough, a bulk fermentation that ended too early, or a hydration that didn't suit your flour. UK fan-oven inaccuracy and hard water are common contributing factors. Diagnose from the crumb, then work through the six fixes below in order.
If you've just sliced a loaf and the centre looks like a yoga mat — same. Dense sourdough is the most reported problem from new home bakers, and almost every case is one of six causes. The good news: the crumb itself tells you which.
Start here. The pattern of the dense bit narrows the cause.
A solid line of dense, slightly damp dough running across the bottom of the loaf, often 1–2cm thick. Cause: under-proofed dough OR oven not hot enough at the base. Check Reasons 2, 5, and 7 below.
Small, regular, evenly distributed bubbles throughout — looks more like a bagel than a sourdough. Cause: under-fermented bulk OR weak starter. Reasons 1 and 2.
The loaf has spread sideways rather than risen up; crumb is uniform and unaerated. Cause: over-fermented bulk (gluten has collapsed) or shaping too loose. Reasons 3 and 5.
One side aerated, the other tight. Cause: uneven mixing, sloppy shaping, or cold spots in your oven. Reason 5 + check oven calibration.
The opposite of the gummy-base pattern. The top of the loaf has fewer bubbles. Cause: shaping too loose at the top, oven too hot at the start (the top set before it could expand), or scoring too shallow.
The single most common cause for new sourdough bakers. A young starter that hasn't been doubling consistently for at least two weeks may bake one decent loaf and then stall.
Test before bake day:
If your starter is failing any of these, see Sourdough Starter Not Rising for the seven-fix protocol.
Move the starter somewhere warmer (24°C). Switch to a 1:2:2 feed for 3 days. Switch the flour to organic wholemeal or rye for the duration. By day 4 you should see consistent doubling. By day 5 it's bake-worthy.
Bulk fermentation is the long first rise after mixing. Most dense loaves were pulled from bulk too early — the dough hadn't yet developed enough internal structure or gas.
| Kitchen temp | Bulk time at 75% hydration | Notes |
|---|---|---|
| 16°C (UK winter) | 10–14 hours | Move dough to a warmer spot. |
| 18°C | 8–10 hours | Slow but workable. |
| 21°C | 5–7 hours | Default assumption in most recipes. |
| 24°C | 4–5 hours | Watch closely past hour 3. |
Bulk is done when:
Most online recipes tell you "bulk for 4 hours" or "bulk until doubled." The first ignores temperature; the second is the wrong target (sourdough at 50% growth is ready, but most people wait for double, by which time it's over-fermented). Reading the dough rather than the clock is the most important habit you can develop.
Less common with beginners, more common with anyone who's read "longer ferment = more flavour" and run with it. Signs: the dough has become very slack, deflated, and feels almost soupy. Loaves spread flat in the oven.
Telltale signs in the crumb: very large, ragged tunnels with thin walls; dense flat shape overall; slightly gummy texture even when cool.
If you suspect over-fermentation has set in, you can cold-retard the dough immediately to slow further activity. Pre-shape gently, place in a banneton seam-up, refrigerate. Bake within 12 hours.
UK flours absorb water at different rates. A 75% hydration with Doves Farm wholemeal feels like 80% with Marriages Strong White.
| Flour | Recommended starting hydration |
|---|---|
| Marriages Strong White | 72–75% |
| Shipton Mill Strong White | 72–76% |
| Doves Farm Stoneground Wholemeal | 78–82% |
| Wessex Mill Cotswold Crunch | 74–78% |
| Shipton Mill Dark Rye | 85%+ (rye is its own beast) |
Use our hydration calculator to dial in the right figures for your flour mix.
Gluten development is what holds the gas in. Skip stretch-and-folds, skip kneading, or shape too loosely and the structure collapses.
To check gluten development: take a small piece of dough between thumbs and fingers. Stretch it gently. If you can pull it thin enough to see light through without it tearing, the gluten is well-developed.
If you're in Kent, London, East Anglia, or much of the South-East, your tap water sits at 250+ ppm. The chlorine in it inhibits wild yeast; the calcium can over-strengthen gluten and slow fermentation.
Fix: leave tap water out overnight, or use bottled still mineral water for both starter feeds and dough mixing.
This is one of those problems that's blamed on the recipe when it's actually water. UK home bakers in hard-water regions often fight an uphill battle for months before realising.
UK domestic ovens are notoriously inaccurate. A buy-once oven thermometer (£8 from Lakeland) often shows your dial at 220°C is actually rendering 195°C.
Buy an oven thermometer. Put it in. Pre-heat to 220°C. Check actual temp after 20 minutes. If it's reading 200°C, dial in 240°C from now on.
If your loaf is dense, ask yourself:
Mid-process saves:
Almost always under-proofing or starter weakness. Check the cross-section: a gummy band at the base is the classic under-proof signature.
Mid-bulk, yes — extend the ferment somewhere warmer. Mid-bake or post-bake, no, but it'll still toast well.
210°C fan for the first 20 minutes (with steam or Dutch-oven lid on), 200°C fan for the next 20–25 minutes uncovered, until the crust is deeply golden.
Yes — but lightly. Wet finger, dent the dough about 1cm. Springs back ¾ = ready. Springs back fully = under-proofed. Doesn't spring back at all = over-proofed.
5–7 hours at 21°C is the typical range for a 75% hydration dough with a healthy starter. Cooler kitchens take longer. Watch the dough, not the clock.
Most likely it doubled and then collapsed before you noticed. Catch it earlier next bake — or you're seeing a tight uniform crumb because the starter isn't yet strong enough.
Cold dough straight from the fridge can cause dense bottoms because the centre takes longer to warm and the dough doesn't fully oven-spring. Let cold-retarded dough warm 30 minutes before baking.
At least 1 hour, preferably 2. Slicing hot sourdough makes the crumb gummy because the starches haven't finished setting.
Either the surface tension was too tight in shaping (creating a barrier) or the dough was too cold when scored. Score deeper, shape with appropriate tension, allow dough to come closer to room temp before scoring.
Clara Ashworth is the founder of The Sourdough Hub. She's diagnosed dense loaves for hundreds of UK home bakers and packs every starter kit by hand from her workshop in Frome, Somerset.
The 1/3/3 rule is a sourdough starter feeding ratio: 1 part starter, 3 parts flour, 3 parts water by weight. A 20 g spoonful...
A sourdough starter is a living culture of wild yeast and lactobacillus bacteria, kept alive in a jar with nothing more than flour and...
A sourdough starter that's not bubbling almost always traces back to one of three things: temperature, feed schedule, or flour. The good news —...