Crumbwise

Guides

Big holes under the crust (tunnels) in sourdough

A big cavern right under the top crust is a classic sign of underproofing — sometimes called 'fool's crumb'.

Why it happens

The dough didn't have enough gas structure when it went into the oven, so the heat blew one big pocket at the top.

Fix

Lengthen bulk fermentation until the dough is 50–75% bigger and bubbly on the sides, or proof a little longer before baking.

Also check shaping

Trapped flour or a loose seam can create a gap. Shape tighter and use less flour on the counter.

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