What permanent wave is made of
Curls that last for months: in 1905 Karl Nessler heated hair wound on rods with electricity; since the late 1930s perms have been set chemically, without heat.
- Heating element — uses. Nessler's first machines heated the wound strands with electric heaters.
- Hair rollers — uses. The strands are wound on perm rods, which are essentially hair rollers.