The Library / When it goes wrong

Big holes, dense everywhere else

A few huge caverns in an otherwise tight, gummy crumb is under-fermentation, however open it looks at first glance.

Why

When a dough hasn't fermented enough, there are too few gas bubbles spread through it. In the oven, what gas there is rushes into a handful of weak spots and blows them up into tunnels, while the dough around them stays dense. Bakers call it fool's crumb, because it looks like the open crumb it isn't.

Further down

A different fault looks similar: one long gap just under the top crust. That is usually an overproofed loaf whose top set while the inside sank away from it, or a pocket of air or flour folded in at shaping. Under-fermented tunnels are scattered through the loaf; the flying crust is a single gap at the top.

Words used here Starter Peak Crumb

Updated 7 October 2026