Steam

Steam at the start of the Baking the loaf is Water as a crust tool. King Arthur Baking: early steam keeps the outside of the loaf moist and flexible so a Crust does not set before Oven spring is finished; the loaf can expand, and surface starches gelatinize into a glossy, shatter-y finish ¹. Calvel's technical baking treats steam as part of the oven sequence for French bread, not as a garnish ².

Steam can be used on pan loaves; it matters most for Hearth bread, where more crust is exposed and the style is lofty and crisp ¹. Professional ovens inject steam, then vent. Most home ovens, especially gas, are built to dump moisture, so the baker has to trap it or add it.

Start wet, finish dry #

Once the loaf has sprung and the crust has started to color, the chamber should go dry so the crust can firm. King Arthur: uncover a Dutch oven or cloche, or pull a steam pan, after about twenty minutes. A spray bottle usually has nothing left by halfway; you do not vent it ¹.

Trap the loaf's own steam — Dutch oven, cloche, covered dish, or a dome over a stone — if the dough is wet enough to throw vapor. Add steam — boiling water in a preheated pan, lava rock, wet towels, or a spray — when you need a freeform shape the pot will not fit. Convection at load dries the oven; they turn it off then, and may use it later to crisp.

Failure #

No steam: tight crust too soon, less height, dull skin. Steam the whole bake: a soft, pale crust that never dries. Opening the door to spray trades heat for a brief cloud. Scoring still has to give the spring a path; steam will not rescue a loaf that was not ready to load.