Oven spring

Oven spring is the burst of rise a loaf goes through in roughly the first ten to fifteen minutes of baking, before the crust sets and the structure firms up. It happens because the sudden heat causes trapped carbon dioxide and water vapor inside the dough to expand quickly, and because yeast activity briefly spikes before the internal temperature climbs high enough to kill it.

Steam plays a major role in a strong oven spring because it keeps the dough's surface soft and stretchy for longer, delaying crust formation so the loaf has more time to expand before it is locked in place. This is the main reason baking in a covered pot or with an added steam source consistently produces taller, more open loaves than baking on an open tray in a dry oven.

A vessel that holds in steam, along with a very hot starting oven temperature, gives dough the best environment to spring well. A common mistake is under-proofing dough hoping for more oven spring, which can work a little but often leads to tearing and dense pockets instead of a clean rise. Just as often, weak scoring or a cool oven is the real cause of flat oven spring, not the dough itself.