Why Does My Sourdough Have a Large Hole Under the Crust?

An open sourdough crumb contains holes of different sizes spread throughout the loaf. The larger holes are surrounded by smaller ones, and the bread between them feels light and properly baked.

A problem cavity looks different. It forms one long tunnel or a single oversized pocket beneath the crust. Below it, the crumb may be tight, heavy, or slightly gummy.

This means the gas did not remain evenly distributed. It collected in one place while the rest of the dough failed to expand at the same rate.

One or two irregular holes in an otherwise beautiful crumb are not necessarily a defect. But when the top of the loaf is almost hollow and the bottom remains dense, the dough usually needed more fermentation before shaping.

Insufficient bulk fermentation is one of the most common reasons for a large hole under the crust.

When dough is shaped before enough fermentation has taken place, it contains fewer small gas cells than a properly fermented dough. The gluten may feel strong, but the interior is still relatively dense.

In the oven, the gases and steam expand rapidly. Because there are not enough well-developed cells throughout the loaf, the pressure finds the easiest place to collect. A large pocket can then form near the top while the lower crumb remains compressed.

Underfermented dough often feels firm and slightly heavy during shaping. It may resist stretching and quickly spring back. There may be a few bubbles on the surface, but the dough does not feel noticeably lighter or aerated inside.

Do not rely only on the number of hours in the recipe. Watch the dough. It should show a visible increase in volume, bubbles along the sides and underneath, smoother edges, and a light movement when the container is gently shaken.

Many wheat sourdoughs are ready for shaping before they double. At a moderate dough temperature, an increase of roughly 30–60 percent may be enough, depending on the flour, hydration, starter amount, and planned final proof.

A starter can double in its jar and still ferment bread dough too slowly.

A small quantity of starter is much easier to lift than an entire batch of dough containing salt and a larger amount of flour. If the starter takes a very long time to peak, falls soon after rising, or has only recently been revived, it may not yet have enough yeast activity for reliable bread fermentation.

Using the starter too early can also cause trouble. It may already contain bubbles but may not have reached its strongest point. A starter used long after its peak can have the opposite problem: much of its available food has been consumed, and its lifting power may already be declining.

For more predictable results, use a mature starter near its peak, when it has clearly risen, contains bubbles throughout, and still has a slightly rounded or level surface.

Not every large hole is caused by fermentation. Sometimes the dough was fermented well, but one large bubble became trapped during shaping.

This often happens when an already inflated section of dough is folded into the centre of the loaf. If the bubble is not noticed, it expands dramatically in the oven and becomes a tunnel.

The answer is not to press all the gas out of the dough. Good sourdough needs those small and medium gas cells. However, an obviously oversized bubble can be gently pressed out before the final shape.

The dough should be shaped deliberately enough to distribute the gas without crushing the entire crumb. Gentle handling does not mean barely touching the dough. The goal is to preserve many small bubbles while preventing one enormous pocket from being sealed inside.

Excess flour on the dough during shaping can create another problem.

If a heavily floured surface is folded into the loaf, the layers may not stick together properly. The dry flour acts as a barrier between them. As the loaf expands, the layers pull apart and create a hollow space.

Try to flour the work surface lightly. The side of the dough that will be folded inward should remain slightly tacky so the layers can join together.

The same problem can occur when oil or a large amount of water becomes trapped between folds. The outside of the dough needs enough friction to create surface tension, while the inner layers need enough contact to seal.

A properly fermented bulk can still produce an uneven crumb if the shaped loaf is baked too soon.

During final proofing, the gas cells recover from shaping and begin expanding again. If this stage is cut very short, the crust may rise quickly in the oven while the dense interior struggles to follow.

Warm dough that is ready to bake usually feels lighter and slightly puffy. A gentle indentation slowly begins to fill back rather than disappearing immediately. The poke test is less reliable on cold dough, so chilled loaves should also be judged by their total fermentation, volume, and feel before refrigeration.

A long cold proof cannot always repair dough that entered the refrigerator seriously underfermented. Cooling slows fermentation, especially after the centre of the loaf becomes cold.

The large hole alone does not provide the entire diagnosis. The crumb around it offers more useful clues.

If the lower crumb is dense, gummy, and filled with very small holes, insufficient fermentation is the most likely cause.

If the crumb is otherwise light and evenly fermented, but there is one smooth, isolated cavity, shaping probably trapped a large bubble or prevented two layers from sealing.

If the dough spread before baking and the crumb looks weak, ragged, or collapsed, fermentation may have gone too far. Overfermented gluten cannot hold individual bubbles, so they can merge into larger irregular spaces.

A very shallow score can also influence where the loaf expands, but scoring alone rarely creates a huge hollow crust. It usually makes an existing fermentation or shaping problem more noticeable.

Begin by giving the dough enough time during bulk fermentation. Keep it at a suitable temperature and look for changes in volume, texture, and aeration instead of following the clock alone.

Use a starter that rises predictably and has been fed regularly. If it doubles but takes most of the day to do so, give it several strengthening feedings before relying on it for bread.

During shaping, remove only the bubbles that are obviously much larger than the others. Use very little flour on the surfaces that will be folded inward, and make sure the layers come into direct contact.

Create enough surface tension to support the loaf, but stop if the outer skin begins to tear. Then allow the shaped dough to proof until it feels lighter and properly aerated.

Changing several things at once can make the real cause difficult to identify. If the problem repeats, adjust one stage at a time—first bulk fermentation, then starter strength, and finally shaping and proofing.

A large hole under the crust usually affects appearance and texture rather than safety.

If the crumb is completely baked and does not contain raw, wet dough, the bread can still be eaten. The hollow slices may be awkward for sandwiches, but they work well for toast, croutons, or breadcrumbs.

A gummy lower crumb may improve after the loaf has cooled completely, but bread that is genuinely raw inside should not be eaten without further baking.

A large cavity under the crust may appear during baking, but the conditions that created it developed much earlier.

The dough may have needed more fermentation, the starter may have lacked strength, or one large bubble may have been folded into the loaf. Sometimes a layer of flour simply prevented the dough from sealing during shaping.

Look at the whole loaf rather than the hole alone. When the surrounding crumb, dough temperature, fermentation, and handling are considered together, that mysterious empty space becomes much easier to explain—and much easier to prevent next time.