Hair Breakage 282 The device consists of a hollow rotating drumlike assembly, where four outer crossbars contain holders for mounting combs or brushes. These outer arms are detachable and allow for use of different combs or brushes. The brushes/combs are mounted at 90-degree angles, allowing one complete drum revolution to brush (or comb) a tress four times. This entire arrangement is duplicated three times in the horizontal direction allowing four tresses to be combed simultaneously. Collection plates are located under each tress to save broken fiber fragments, while spacer plates on the rotating drum prevent cross-contamination. By adopting learning from the single fiber fatigue work, it becomes possible to recognize how a number of variables can influence the outcome of these experiments. For example, a combination of the size and shape of hair tresses, the tooth-spacing of the brush or comb, and the condition of the hair will all dictate the magnitude of the grooming stresses and consequently influence the amount of breakage. In addition, the need for performing experiments under controlled humidity conditions is apparent. A more comprehensive discussion involving the contribution of these variables has been given previously.12 Results: Figure 22 shows a Box & Whisker plot for the number of broken fibers arising from repeated grooming of virgin Caucasian hair treated with a commercially available conditioner product relative to an unconditioned state. Results convincingly illustrate the benefit provided by such products, in that the extent of breakage in this particular instance has been reduced by approximately 60%. However, with some slight modification to the method, it becomes possible to perform Weibull analyses and model the tendency for breakage throughout the experiment. Grouped Weibull analysis: Table 10 shows how repeated grooming experiments can be setup in a manner that allows for performing a grouped Weibull analysis.6 It is seen that the number of broken fibers is evaluated at regular intervals throughout the experiment. Column 2 shows the total number of broken fibers (from eight replicate hair tresses) after grooming in 1,000 cycle