Diagnosing Your Bread by the Crumb

The crumb is your bake report card. Different problems leave different signatures. Here's how to read them.

The healthy crumb

Even, irregular holes throughout. Holes ½ to 1 inch in size. Glossy walls between holes. No undercooked patches. Cuts cleanly without compressing.

Tight, dense crumb

What it looks like — small, uniform holes throughout. Heavy, packed structure. Bread feels weighty.

Most common cause — under-fermented bulk. The dough didn't have enough time for yeast to produce gas.

Less common causes — weak starter, low hydration, cold environment.

Fix — extend bulk fermentation. Let it rise 50–70%. Use a stronger starter.

Tunneling under the crust

What it looks like — one giant air pocket under the top crust. Crumb below is denser.

Cause — improper shaping. The dough wasn't sealed underneath; gas accumulated at the top during the final proof.

Fix — better shaping technique. Build surface tension on top by dragging the dough across the counter. Pinch the bottom seam closed.

Wide irregular holes throughout

What it looks like — large holes (1+ inches) of varying sizes throughout the loaf. Wild, open structure.

Cause — high hydration combined with proper fermentation. This is typically Tartine-style intentional, not a problem.

Fix — none, if this is what you wanted. If not, lower hydration.

All small holes, but loaf is risen

What it looks like — uniform tiny holes, but the loaf has good height.

Cause — over-mixed dough or under-fermented despite the rise.

Fix — less mixing. More fermentation time. Allow gluten to develop through folding rather than kneading.

Gummy patches

What it looks like — sections of the loaf are wet, sticky, almost custardy.

Cause — under-baked. The starches didn't fully set.

Fix — bake longer. Verify internal temperature is 207–210°F. Use a thermometer, not just visual cues.

Pale, dense bottom

What it looks like — the bottom of the loaf is light-colored and denser than the rest.

Cause — bottom heat insufficient. Often happens when baking on a regular sheet pan instead of a stone or in a Dutch oven.

Fix — preheat a baking stone or steel. Use a Dutch oven. Place rack lower in the oven.

Sour pockets and uneven color

What it looks like — some sections darker, some lighter. Smell varies across the loaf.

Cause — uneven mixing. The starter wasn't fully distributed.

Fix — better initial mixing. Make sure starter and water are fully combined before adding flour. Mix until completely uniform.

Collapsed top, dense interior

What it looks like — the loaf rose then sank, leaving a flat or sunken top with dense crumb.

Cause — over-proofed. The dough exhausted its gas-trapping capability before the bake.

Fix — shorter final proof. Bake when the dough is springy but not at maximum puff.

Crumb separating from crust

What it looks like — visible gap between the interior bread and the crust.

Cause — over-proofed, or the dough was over-floured before scoring.

Fix — shorter proof. Less surface flour. Score deeply enough to control expansion.

Spongy, evenly fluffy crumb

What it looks like — uniform, soft, sandwich-bread-like crumb.

Cause — high commercial yeast content (if added), or very long, slow fermentation in a soft dough.

Fix — none, if intentional. This is great for sandwich bread.

Closed crumb in the bottom third

What it looks like — open crumb on top, dense crumb on the bottom.

Cause — gas migrated upward during a long final proof. The bottom got squished.

Fix — shorter final proof. Bake straight from cold-proof.

Diagnostic checklist

When evaluating crumb:

1. Is it uniform or uneven?
2. Are the holes irregular (good) or perfectly uniform (over-mixed)?
3. Is the texture springy or compressed?
4. Are there any wet patches?
5. Does it cut cleanly?
6. Is the bottom the same as the top?

Each answer points to a step in the process to adjust.

A learning exercise

Slice your bread carefully. Take a photo. Note your conditions: hydration, bulk time, proof time, bake temperature.

Build a library of your own crumb shots over 20 bakes. Patterns emerge fast — you'll see exactly which adjustments produced which results.

Your crumb is a story written in dough. Reading it well is one of the slowest, most rewarding parts of becoming a baker.