Five sections covering starters, crumb structure, crust, fermentation timing, and advanced technique — so you know exactly what went wrong and how to correct it.
Start diagnosing →A weak or inconsistent starter is the most common reason sourdough fails. Before blaming your technique, check the source.
If there's no visible activity within 12 hours of feeding, the culture is too cold or too diluted. Move it somewhere 24–27 °C and use a 1:1:1 feeding ratio (starter : flour : water by weight) until it doubles reliably.
A grey liquid layer means the starter is hungry — it ran out of food and began producing alcohol. Discard down to 20 g and feed more frequently, or increase the flour-to-starter ratio in your feed.
Sharp acetone or nail-polish remells signal over-fermentation. A healthy starter smells pleasantly tangy — sour yogurt or mild vinegar. If it smells putrid or has pink/orange streaks, discard it entirely and start again.
The float test is unreliable — a gassy starter floats even when the yeast isn't strong enough for a full bake. Use the dome-peak timing method instead: use the starter at peak rise, just before it begins to fall.
The crumb tells you almost everything about what went wrong. Each pattern has a specific cause — here's how to read them.
Loaf feels heavy and wet inside even after full bake time. Slices compact under the knife.
Extend bulk fermentation by 30–60 min (dough should be 50–75% larger and feel airy). Ensure internal temp reaches 96–98 °C before pulling from the oven.
Some parts of the crumb have large tunnels; others are dense. Inconsistent throughout.
Uneven crumb usually means air pockets weren't properly redistributed during shaping. Practice a tighter pre-shape and allow a proper bench rest of 20–30 minutes before final shaping.
The loaf sliced like dense bread. No visible gas cells at all.
Either the dough wasn't developed enough (add 2–3 more stretch-and-fold sets) or it over-proofed in the banneton (reduce cold retard time or refrigerate sooner). A poke test — indent springs back slowly but fully — confirms correct proof.
A large air pocket sits just under the top crust, separated from the crumb below.
The skin of the loaf separated from the crumb before full spring. Over-proofing is the usual cause — the dough can't support itself as it expands. Slightly reduce bulk ferment or cold proof time.
Crust issues are mostly oven problems. Temperature, steam, and timing work together — getting any one wrong shows up immediately on the outside of the loaf.
Your oven isn't hot enough, or you're opening the lid too early. Preheat your Dutch oven for at least 45–60 minutes at 250 °C (480 °F). Keep the lid on for the full first 20 minutes to trap steam, which gelatinises the surface and enables colour.
The lid came off too early, or the oven runs hot. Drop the temperature by 10–15 °C after removing the lid and bake uncovered for a longer period at the lower temp. A leave-in thermometer confirms your oven's actual calibration.
The score was too shallow or at the wrong angle. Score at a 30–45 degree angle (not straight down), at least 1.5 cm deep, with a single decisive cut. A lame or sharp razor blade is non-negotiable — a standard knife drags and seals the dough.
Condensation from a warm loaf in a confined space re-softens the crust. Always cool on a wire rack in open air for at least 2 hours before slicing or storing. Don't bag the loaf while it's still warm.
Minor cracking is normal and desirable. Extreme post-bake cracking usually means the loaf dried out too fast — lower the oven temp slightly in the final uncovered phase, or bake in a more humid environment.
Fermentation doesn't run on a clock — it runs on temperature, starter strength, and flour type. Understanding the signals matters more than following a recipe's timing exactly.
A recipe says "4–6 hours" because it was written at a specific room temperature. Your kitchen at 20 °C will run slower than 26 °C. Watch for 50–75% volume increase, a domed surface, and jiggly, airy texture when you shake the container.
Every 5 °C change roughly halves or doubles fermentation speed. Keep a thermometer in your kitchen. If your bulk is running too fast, move the dough somewhere cooler — even 2–3 degrees makes a material difference.
Shaping and refrigerating overnight (8–16 hours at 4 °C) slows fermentation nearly to a halt and gives you baking flexibility. It also develops flavour. If your schedule shifts, the fridge buys you hours.
Whole grain flours contain more wild yeast and bacteria than white flour. If you substitute even 10–20% whole wheat into a white flour recipe, expect fermentation to move 20–30% faster. Adjust accordingly.
Press your finger about 1 cm into the shaped loaf. Under-proofed: springs back immediately and completely. Ready: springs back slowly and mostly (a small indent remains). Over-proofed: doesn't spring back at all — bake it now anyway.
A slightly under-proofed loaf is recoverable — it bakes with good oven spring and a tight crumb. An over-proofed loaf that sits even longer deflates further. When you're on the edge, bake; don't wait.
Quick answers to the questions that come up again and again.