Why Is There a Big Hole Under My Bread Crust

You slice a loaf that looked perfect from the outside and find a long empty pocket right below the top crust, with a dense band of crumb underneath. Bakers call this a flying crust or tunneling. The crust lifted away from the crumb because gas gathered in one place instead of spreading evenly through the dough.

The pocket is a clue, not a mystery. Its shape and position tell you whether the dough went into the oven too early, whether air got trapped during shaping, or whether the top of the loaf hardened before the dough finished expanding. Work through the causes below in order; the first two account for most cases.

Read the hole before you change anything

A single wide gap that follows the curve of the top crust, with tight crumb below it, almost always means the loaf was underproofed or the crust set too soon. The dough still had plenty of gas left to give when it hit the heat, and the expanding interior pushed the soft top layer up like a lid.

A spiral gap or a tunnel that runs the length of the loaf, sometimes with a floury line along it, is a shaping problem. The layers you rolled never fused, so they separated as the bread rose. In swirl breads, a gap next to the filling is the same issue made worse by sugar and butter between the layers.

• Gap follows the crust, dense crumb below: proofing or crust setting
• Spiral or lengthwise tunnel: loose shaping or excess dusting flour
• Gap beside a cinnamon or chocolate filling: layers did not bond around the filling

Underproofing and how to judge the final rise

Dough that goes into the oven before its final rise is finished has a lot of yeast activity still ahead of it. In the first minutes of baking that activity speeds up, the gas expands quickly, and the weakest spot gives way. In a loaf pan that weak spot is usually just beneath the top surface.

Clock times in recipes assume a certain kitchen temperature. In a cool room a sandwich loaf can take twice as long as the recipe says. Use the dough rather than the timer: a pan loaf is usually ready when the dome rises about 2.5 cm (1 in) above the rim for a standard 23 x 13 cm (9 x 5 in) pan, and a gentle press with a floured finger leaves a dent that springs back slowly and not completely. If the dent springs back at once, give it more time.

Shaping that leaves trapped air or open seams

Before shaping, press the dough firmly to push out large bubbles. Big pockets left in the dough at this stage do not disappear; they grow. When you roll a sandwich loaf, roll it tightly and press each turn into the one before with your thumbs, then pinch the final seam hard and set the loaf in the pan seam side down.

Use as little flour as possible on the counter during shaping. A dusty surface keeps the layers from sticking to each other, and that floury film becomes the line where the loaf splits. If the dough is tacky, a light film of oil or a damp hand works better than more flour. For swirl breads, leave a 2 cm (¾ in) border bare of filling on the far edge so the seam can seal, and keep the filling to a thin, even layer.

When the crust sets too early

If the surface of the dough dries out during the final rise, it forms a leathery skin that cannot stretch. Cover the loaf with a lightly oiled sheet of plastic, a clean shower cap or an upturned bowl. The same thing happens in the oven when there is no moisture in the air: the top hardens in the first few minutes while the interior is still expanding.

Steam during the first 10 to 15 minutes keeps a free-form loaf supple, and a few confident slashes give the dough a planned place to open. For pan loaves, a very hot top element or a rack placed too high can brown and firm the crown too fast. Bake on the middle rack and tent loosely with foil only if the top darkens before the loaf is done.

Other contributors worth checking

Very strong flour with low hydration makes a tight, elastic dough that resists expanding evenly, so the gas collects where it can. A dough that is a little softer usually rises more uniformly. An oven that runs hotter than its dial can also cause a burst of spring followed by an early-setting crust, so an inexpensive oven thermometer is worth having.

Finally, check doneness. A loaf pulled while the center is still soft can sink slightly under the crust as it cools, which widens a small gap into a visible one. Most lean sandwich loaves are done at about 88 to 93°C (190 to 200°F) in the center, and enriched loaves at about 85 to 88°C (185 to 190°F).

• Slightly higher hydration for very stiff doughs
• An oven thermometer to confirm the real temperature
• Bake to the internal temperature, not just crust color

Common questions

Can I still eat bread with a hole under the crust?

Yes. The bread is fully baked and safe to eat; only the texture is uneven. Slices with a big gap tear easily, so use them for toast, croutons or bread pudding, and adjust proofing or shaping on the next bake.

Why does only my cinnamon swirl bread get gaps?

Sugar, butter and cinnamon act as a barrier between the dough layers, and the filling releases moisture that turns to steam. Spread the filling thinly, skip melted butter in favor of a light brush of egg or milk, roll tightly and proof fully before baking.

Is the poke test reliable for pan loaves?

It is a good guide when combined with height. Dough that has crested about 2.5 cm (1 in) above the rim and springs back slowly from a gentle press is usually ready. Very soft enriched doughs spring back less, so lean more on height for those.