and the hot air. If steam is present, it provides
an initial blast of heat by condensing onto the
cold dough surface. Heat then moves from the
surface through the dough by two means: slow
conduction through the viscous gluten-starch
matrix, and much more rapid steam
movement through the network of gas
bubbles. The better leavened the dough, the
faster steam can move through it, and so the
faster the loaf cooks.
As the dough heats up, it becomes more
fluid, its gas cells expand, and the dough rises.
The main cause of this oven spring is the
vaporization of alcohol and water into gases
that fill the gas cells, and that expand the
dough by as much as half its initial volume.
Oven spring is usually over after 6–8 minutes
of baking.
Mid-Baking: From Foam to Sponge Oven
spring stops when the crust becomes firm and
stiff enough to resist it, and when the interior