A loaf can look beautiful when it first comes out of the oven. The crust is golden, the bread has risen well, and everything seems successful. Then, while it is cooling, the top begins to sink. Sometimes only the center dips slightly. In other cases, the whole loaf loses height and looks as though the air has slowly escaped from it.

When sourdough bread collapses after baking, the problem usually began before the loaf left the oven. The crust may have looked finished, but the structure inside was not strong enough to support the bread as it cooled.

One of the most common reasons is simple: the bread was removed from the oven too early.

A dark or golden crust does not always mean the center is fully baked. This is especially true with large loaves, high-hydration dough, enriched dough, or bread baked at a very high temperature. The outside colors quickly while the center remains moist and weak.

Inside the oven, hot gases and steam keep the loaf expanded. Once the bread is removed, the temperature drops and the steam begins to condense. If the crumb has not set firmly enough, it cannot hold its shape and begins to sink.

A collapsed loaf may feel unusually heavy for its size. When cut, the crumb can be damp, gummy, compressed near the bottom, or slightly shiny around the larger holes.

For a typical wheat sourdough loaf, the internal temperature is usually around 96–99°C (205–210°F) when fully baked. Temperature is useful, but it should not be the only guide. A large or very wet loaf may still need several extra minutes to dry and strengthen the crumb.

An overproofed loaf may still rise in the oven, but its structure is already close to breaking down.

During fermentation, yeast and bacteria produce gas while gluten holds that gas inside the dough. If fermentation continues for too long, the gluten becomes increasingly stretched and weakened. Eventually, the dough no longer has enough strength to support itself.

The loaf may look impressively inflated before baking, but that volume can be deceptive. Instead of containing a strong network of small, elastic gas cells, the dough may be held up by thin, fragile walls.

In the oven, those walls expand one last time. After baking, they contract and may collapse.

An overproofed loaf often has several signs:

Cold dough can still overproof in the refrigerator. The refrigerator slows fermentation, but it does not stop it immediately. A warm dough placed into a refrigerator may continue fermenting actively for several hours before the center becomes cold.

A loaf needs more than gas to rise. It also needs a strong framework capable of holding that gas after baking.

Weak gluten can result from flour with insufficient protein, inadequate dough development, excessive fermentation, or too much mechanical damage during shaping.

Sometimes the dough rises well in the bowl because the container supports it. Once shaped and baked, however, the weakness becomes obvious. The loaf expands but cannot maintain its height.

This is particularly common with very wet dough. Adding more water can create a lighter, more open crumb, but only when the flour and gluten development can support it. If hydration is pushed beyond what the dough can handle, the loaf may look large in the oven and then settle as it cools.

The answer is not always to add more flour. Often it is better to reduce the water slightly, strengthen the dough during bulk fermentation, and shape with enough surface tension to create a supportive outer skin.

A loaf with one or two enormous holes may collapse even when the rest of the crumb is baked.

Large tunnels leave less internal structure to support the crust. As the hot air inside those cavities cools, the pressure drops. If the surrounding crumb walls are thin, the top of the loaf can sink into the empty space.

These large cavities may develop when shaping traps pockets of air, when bulk fermentation is uneven, or when the dough is underproofed before baking. An underproofed loaf can produce dramatic oven spring, but the expansion may be irregular rather than evenly distributed through the crumb.

This is why a loaf can be both underproofed and partially collapsed. The bread rises sharply in the oven, forms a few oversized cavities, and then loses some of that height while cooling.

Fresh bread continues changing after it leaves the oven. Steam moves from the center toward the crust, and the crumb gradually becomes stable.

If the hot loaf is placed on a solid surface, covered immediately, or left inside a pan for too long, moisture can become trapped. The bottom and sides soften, and the crumb may remain wetter than expected.

This usually causes less dramatic collapse than underbaking or overproofing, but it can make an already weak loaf sink further.

Let the bread cool on a wire rack with air circulating around it. Avoid cutting it while it is still hot. A wheat sourdough loaf generally needs at least two hours, and a large or very moist loaf may need longer.

Cutting too early does not usually make the entire loaf collapse, but it releases steam before the crumb has finished setting and can leave the inside gummy and compressed.

Not every small change in shape is a failure.

Bread naturally contracts slightly as it cools. Steam escapes, gases shrink, and the crust softens a little. A small reduction in height is normal, especially with soft sandwich loaves and highly hydrated bread.

A genuine collapse is more noticeable. The top develops a deep hollow, the sides pull inward, or the crumb becomes compressed beneath the crust.

The timing also provides a clue. If the loaf sinks immediately after leaving the oven, underbaking or weak structure is likely. If it looked flat before baking or deflated during scoring, overproofing is more likely. If the collapse is concentrated above one huge hole, the issue probably began during fermentation or shaping.

The best correction depends on what the crumb reveals.

A wet, gummy crumb needs more baking time. A very open loaf with thin, fragile walls may need slightly less fermentation or lower hydration. A loaf with one enormous cavity needs more even fermentation and gentler, more controlled shaping.

Do not change everything at once. Choose the most likely cause and adjust one part of the process in the next bake.

Bake the loaf a little longer. End proofing earlier. Reduce the water by a small amount. Strengthen the dough more during bulk fermentation. Then compare the result.

Sourdough rarely collapses for no reason. The finished loaf is showing you where its structure became too weak. Once you learn to read those signs, the next bake becomes much easier to correct.