You cut into a sourdough loaf and something is off. Either the crumb is dense and gummy at the bottom with a gaping hole near the top, or the bread looks flat and pale with no real oven spring at all. Both are common. Both are fixable. And both come from the same root issue: the dough was at the wrong stage of fermentation when it went into the oven.
The hard part is figuring out which problem you have. Underproofed and overproofed loaves can sometimes look surprisingly similar from the outside, but the fix for each is the opposite of the other. Get the diagnosis right and you'll save yourself a lot of bad bakes.
In sourdough, fermentation happens in two stages.
Bulk fermentation — the long rise after mixing, before shaping. This is where most of the rise and flavor development happens.
Final proof (also called second rise or "proof") — the rest after shaping, before baking. This is shorter and gentler.
When people say a loaf is "underproofed" or "overproofed," they usually mean across both stages combined. A bread can be perfectly proofed in the second rise but underbulked in the first — the result still looks underproofed in the final loaf. So the diagnosis is really about whether the total fermentation hit the sweet spot, not just one stage.
For more on the bulk stage specifically, the bulk fermentation guide covers what to watch for during the first rise.
Before the bake — what to watch for in the dough:
After the bake, an underproofed loaf typically shows:
The classic underproof signature is the contrast between the crumb top and bottom: a hollow chamber up high and dense, almost gummy bread down low. The yeast didn't have time to evenly distribute gas through the dough, so it concentrated in one weak spot during oven spring.
Before the bake — what to watch for:
After the bake, an overproofed loaf typically shows:
The signature of overproofing is a flat, dense, sad-looking loaf with overdone sourness. It's a loaf that gave up before reaching the oven.
Both extremes can produce a tight, dense crumb — which is why people misdiagnose them. Here's how to tell them apart at a glance:
| Symptom | Underproofed | Overproofed |
|---|---|---|
| Oven spring | Often dramatic, possibly uneven | Minimal or none |
| Crust color | Pale to normal | Often pale, sometimes patchy |
| Crumb structure | Dense bottom, sometimes hollow top | Tight throughout, often gummy |
| Score / ear | Big ear, dramatic crack | No ear, flat lines |
| Taste | Mild, almost yeasty | Sharply sour, sometimes harsh |
| Loaf shape | Stands tall, possibly bulging at top | Flat, spread outward |
| Smell when cut | Mild, slightly raw | Strongly tangy, sometimes acetone-like |
The single fastest tell: oven spring. An underproofed loaf wants to spring. The yeast is alive, the gluten is strong, the dough was just behind schedule — so it explodes upward in the oven, even if the spring is uneven. An overproofed loaf has nothing left to give. The yeast is exhausted, the gluten is weak, and the dough sits there.
If your loaf has dramatic, sometimes ugly oven spring with weird shapes, you're underproofed. If it sits there flat and pale, you're overproofed.
The most common reasons:
Cold dough temperature. A dough at 21°C ferments much slower than one at 26°C. If your kitchen is cold and the recipe assumed warm conditions, you'll underproof on the recipe's clock.
Weak or recently fed starter. A starter that hasn't fully built up yeast population won't drive bulk fermentation hard enough. Use starter at peak — when it has roughly doubled and is just starting to dome — for best activity.
Cutting bulk short to fit a schedule. Sometimes the dough simply needed another hour but you needed to leave the house. The clock wins, the dough loses, the bread suffers.
Reducing starter percentage. Halving the starter to "make it more sour" often just makes it underproofed. Less inoculation needs more time, not the same amount of time.
Using cold water at mixing in winter. This drops the dough temperature 2–4°C below the recipe assumption from the start.
The most common reasons:
Warm kitchen. A summer kitchen at 28°C will outpace a winter recipe by hours. Doughs in hot rooms can finish bulk in 2.5 hours when the recipe says 4.
Walking away too long. The last hour of bulk moves faster than the first. A "I'll check in 90 minutes" plan often comes back to an overproofed mess.
Long retard plus warm bulk. If you've already pushed bulk to the edge and then put the dough in the fridge for 24 hours, the cold doesn't always stop fermentation completely — it just slows it. The dough can still go past the line overnight.
Very active starter at warm temperatures. A young, hungry starter at 27°C can power a dough through fermentation faster than expected, especially with high-protein flour.
Too much starter. A 30%+ inoculation drives fermentation hard. If you've increased starter percentage to "speed things up," you also need to shorten bulk significantly.
If you catch it before the bake — say you've shaped, and now you realize the dough is barely risen — you have options:
After the bake, there's not much to do. An underproofed loaf is what it is. Slice thinner, toast aggressively, or use it for French toast — both of which mask the dense crumb.
This is harder, because overproofed dough has lost structure that you can't easily get back. Options:
The hard truth: a badly overproofed loaf usually can't be saved into a great-looking boule. Learn from it and adjust the next bake.
The path to consistently well-proofed bread isn't reading more recipes. It's repeating the same recipe in your kitchen, with your starter, at your temperatures, multiple times — and adjusting one variable at a time.
A practical experiment that works for almost everyone:
After three or four bakes, you'll have a strong sense of how long bulk takes at your house. After ten, you'll be able to look at a dough and just know.
Next time a loaf comes out wrong, ask:
Bread is a slow teacher, but a patient one. Every loaf — even the bad ones — is feedback you can use.
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