26. Is slashing of loaves aesthetic or functional?

Both.

Historically, French rural ovens were communal, in a sense: they were
originally owned by the lord, and maintained by a fournier, or
ovenmaster, who kept the oven hot but charged for its use.  Since the
bread of each household would be mixed with others in the oven, a
distinctive slash was one way to tell the loaves apart. After the
feudal power of other lords (and the Church, which also controlled
many ovens) was broken, the ovens were (and are, in places like
Bugey, in Eastern France) owned by the "commune", the governmental
body of the city or district. The are still used on holidays, and the
bread is still distinctively slashed.

Anyway, bread which is not baked in a pan and which is not proofed in
a 100% humidity environment will almost always burst as it is baked,
and the burst is uncontrolled and messy.  The slash controls this,
but is also decorative - it enhances the vitality of the process...
as the burst shows how well the baker matched the rising power of the
leaven to the mechanical properties of the gluten. A nice slash and
shred is a sign of proficiency in baking.

Whole grain breads that do not rise or spring as markedly do not need
to be slashed if they are proofed in a high-humidity environment.

-Dan

Additionally slashing prevents a "flying crust." Flying crust is a
term describing the lifting of the entire upper crust of a loaf
during baking to form one large bubble.

Darrell