hen the permanent wave debuted in 1906, the hair treatment took six to 12 hours to complete using a combination of chemicals and an electrical heating device. However, only upper-middle-class women could afford the hefty price tag equivalent to roughly $23,000 today. But by the mid-1920s, the permanent wave’s price had been buzz cut for the masses, and the treatment began appearing at expos such as this beauty-care products show in Los Angeles. While early versions worked only on Rapunzel-length locks, a new method pictured here was invented in 1924 for bobbed tresses.