Why a gas oven makes it difficult to steam bread

Baking bread with steam is essential for obtaining large loaves with an open crumb and a golden, crispy crust. In a dry oven, the crust hardens quickly, preventing the dough from fully expanding, and the crumb becomes denser. If steam is present from the start, the crust remains flexible, the bread can stretch before setting, and the crumb is lighter and more open.

In addition, the steam helps to gelatinize the surface starches, which promotes browning and a particularly crispy and shiny finish.

There are several ways to steam bread, all aimed at introducing moisture during the initial part of baking. The most common method involves placing a large cast-iron skillet under the baking stone or hob while the oven preheats. After placing the bread inside, a cup of warm water is immediately poured into the preheated skillet, and the oven door is quickly closed to prevent the steam from escaping.

This method works well with one exception: it's not effective in a gas oven. By design, these ovens expel exhaust gases, so the steam quickly dissipates from the chamber. All the water evaporates in a short time, leaving insufficient moisture to improve the crust.

There's an alternative: baking the bread in a preheated lidded pot, such as a cast iron pot. Instead of adding water, the lid traps the steam released by the bread itself during baking, and because it's sealed, the gas oven doesn't expel it. A cast iron pot works for round loaves; for oblong loaves shaped like bâtards, a steel loaf pan with a lid, such as the one from Brod & Taylor, which also comes in a round version, is ideal.

To generate even more steam with the lid on, you can place a few ice cubes between the baking paper and the tray when you put the dough in. Make sure the paper is underneath the dough; otherwise, the melting ice could cause the bread to stick to the tray.