Bubble Under Crust
Here are some helpful solutions for the common causes:
No slash or vent in loaf
This recipe may require a slash or vent for the gas bubbles to escape while the dough is baking. Make an angled cut on the top of the loaf with a sharp knife before baking.
Oven temperature too hot
When the oven is too hot, the crust forms before all the steam has escaped from the loaf. This causes bubbles to build up under crust. The oven temperature may not be correct. To insure the correct temperature each time you bake, always use an oven thermometer. Place it in the center of the oven. Adjust oven dial up or down to correct the oven temperature.