Collection of pictures showing sourdough bread with different problems and the possible reasons for the problems.
I have sourced the pictures and the reason suggestions from a sourdough facebook group, I am a member of.
Space between crumb and top crust.
Sourdough starter is too weak.
The bread is raw in the middle.
Maybe the starter was not strong enough.
Maybe not enough bulk fermentation.
More examples :
Tunneling is a symptom of under proofing
Dense spots around the middle.
Maybe baked to short time.
Maybe baked with too low a temperature.
The bread have had no oven spring and is flat
Maybe the dough have been proofing too long time typically second proofing on the counter instead of in the fridge.
Maybe too little Stretch & Fold so that the gluten have not been developed.
Steam & gas created inside the bread creates an unwanted blowout then trying to escape.
Maybe no scoring or scoring not deep enough.
Maybe the crust hardened too fast for the inside steam to escape through the scoring, which can happen if there is no steam in the oven to delay crust hardening, eg. if not baking in a DO.
Uneven or under ferment
A few big holes typically at the bottom of the bread and otherwise only small holes.
Maybe uneven distributed yeast.
Maybe underdeveloped or overdeveloped leaven.