Chapter 5 163 The helical coil method can be used to study the effects of treatments on set or for fundamental studies of factors affecting the settability of hair. Ciavarella7 collected gray and pigmented hairs from 11 individuals with “salt and pepper” hair and measured these hairs’ ability to take a temporary set using the helical coil method. Six gray and six pigmented hairs from each individual were tested using this methodology. Bending set was measured at 1 min and 22 h after removal from the setting rods. Results are shown in Figure 5. Gray hair was less settable and held set less well compared to pigmented hair. Interestingly, there was no difference in set for some individuals, but for some others gray hair was dramatically less settable. This supports the contention of some consumers that their gray hair is “unmanageable.” Permanent Waving of Hair Waving chemistry: Temporary set relies entirely on physical changes in the hair and is quickly lost in water, not to mention being notoriously sensitive to relative humidity. The production of permanent set that is resistant to water and humidity requires chemical modification. The modern cold waving process was invented in the early 1940s as the “thiol cold wave”15 and was quickly developed into product forms that remain quite recognizable today.16 Figure 5 Bending set at 1 min and 22 h post release for gray and pigmented hairs from the same individuals. Pigmented hair held set significantly better.