Ultrafire Crack Repair KitUltrafire Brick Oven Crack Repair Kit by Authentic Pizza Ovens Even though you cure your oven, it will still crack. Realistically, all wood fired brick or clay ovens will crack at varying degrees. These cracks are usually very thin. While patching cracks isn't necessary as it does not affect the oven's function, we do recommend a "patch" kit to cover any cosmetic fixes that arise. Check out the video below to see how it works!