PROFILOMETRY OF HAIR 37 180 360 540 720 900 1080 1260 1440 1620 1800 time in sec a) 0 90 180 270 360 450 540 630 720 810 900 b) time in sec Figure 12. Change of roughness parameters, Rq, during drying at ambient condition (above) and using a fan (below). scans of the same hair segment was performed at constant time intervals while the samples were dried with and without the use of a hair drier. The two figures demonstrate the change in surface roughness as the hair becomes dry Rq is reduced by approximately 10% in both treatments. All these results are in agree- ment with the increased combing resistance for wet hair (8). Figure 13 shows that a treatment of hair with shampoo (in vitro assay, 30øC, 1% solu- tion of shampoo, 90 min of treatment) decreases the roughness parameters but keeps Pc constant (Figure 14). The reason could be the removal of debris or loosely adhering cellular material. Figure 15 demonstrates the influence of two shampoos used every other day for three weeks by 20 volunteers. Shampoo B, which reduced the total profile length signifi- cantly, was characterized as not contributing to "body" and "resilience." Apparently loss of profile length decreases the number of contact points and the adhesion between different hair fibers.

38 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS w w ! w z Rz Figure 13. Mean values of roughness parameters of 20 hair fibers before and after shampoo treatment scanned at different distances from the root (scan length 0.40 mm). TRANSVERSE MEASUREMENTS Several difficulties had to be overcome before reliable data could be obtained: a) stretching and bending of the hair fiber during stylus contact can be recognized by systematically skewed signals this could be avoided by using the instrument illus- trated in Figure 3 Po Figure 14. Mean values of actual profile length and peak count of 20 hair fibers before and after shampoo treatment scanned at different distances from the root (scan length 0.40 mm).