Hair Care Product Claims 508 possessing the same charge, which subsequently results in an unruly flyaway appearance. The lifetime of this surface charge is dependent on the ease by which it can be conducted away, which itself relates to the moisture content of hair. Therefore, as described in Chapter 10, a low humidity environment dictates diminished moisture content and reduced tendency for charge dissipation. Consequently, static electricity buildup during grooming becomes an issue under these conditions (see Figure 8). Approaches to mitigate this issue involve reducing the amount of charge generated and/or increasing its mobility. A seminal paper on measuring static buildup in hair involves the work of Lunn and Evans,3 who addressed both of these areas. One experimental procedure utilized a Faraday cage to measure the amount of charge generated during repeated combing of hair, while a second involved an ability to impart a charge on the hair followed by monitoring of the decay rate. Figure 9 shows the custom-built device used at TRI-Princeton for evaluating static charge buildup. Hair tresses are brushed in a reproducible manner by a rotating arm, while a specifically positioned sensor measures the resulting charge. The apparatus is small enough to be encased in a bench-top Figure 8. Buildup of static charge upon grooming hair in different relative humidity conditions