Blonde Girl At Home Wearing Hair Rollers

The diameter of a roller varies from approximately 0.8 inches (20 mm) to 1.5 inches (38 mm). The hair is heated, and the rollers strain and break the hydrogen bonds[citation needed] of each hair's cortex, which causes the hair to curl. The hydrogen bonds reform after the hair is moistened.
A hot roller or hot curler is designed to be heated in an electric chamber before one rolls it into the hair. Alternatively, a hair dryer heats the hair after the rolls are in place. Hair spray can temporarily fix curled hair in place.
In 1966, Panasonic produced the first electrically-heated hair rollers, and released them in Japan.