Want to maximize your oven spring without buying a $5,000 commercial bakery steam oven? Use the Ice Cube Hack! When you transfer your scored dough into your pre-heated cast iron Dutch oven, carefully drop one or two standard ice cubes right between the parchment paper and the blistering hot iron wall (make sure the ice doesn't touch the dough directly). Instantly clamp the heavy lid shut. The ice flash-melts, creating a hyper-humid micro-environment. This keeps the exterior crust soft and pliable, allowing the bread to expand massively before the crust finally hardens and sets into a shattered shell.