To get blisters, two things are required: 1. Build tension in the dough by "stitching the dough" in the banneton after you have shaped it and let it relax for a few minutes. Pull the dough from each side of the loaf and overlap them. (See the video. This is difficult to describe) 2. Spray the crust thoroughly with refrigerator-cold water. Then, bake inside a pre-heated Dutch oven with the lid on at high heat