452 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS 200 160 120 80 • .... # Right side: D.H. Left side: V.G.H. o o ! J I I I 60 80 100 Time after shampoo (h) Figure 14. Reoiling rate of hair in vivo after shampooing with different shampoos. Ordinate represents length of hair coated with sebum abcissa time since last shampooing. DH--shampoo for dry hair VGH--Shampoo for very oily hair. (Reproduced with permission from ref. 9). criteria judging oiliness of hair appear to be lack of luster and the clumping together (rat-tailing) of hair fibers (5). The duller the appearance of the hair and the more the fibers are clumped into bundles, the oilier and dirtier is hair judged. To demonstrate this, Leduc, et al. (9) measured the average spacing between hair fibers as a function of time after shampooing and found considerable decline in the values of interfibrillar spacings (Figure 15). The magnitude of the effect depended on the nature of the shampoo used and correlated with subjective assessment of the state of oiliness. Our own investigation led to similar results (27). We treated hair tresses with two types of oil repellent, cationic compounds of differing concentrations and then with a 0.5% hexane solution of sebum. All tresses displayed some stringy appearance characteristic for oily hair (Figure 16), however when tresses were ranked visually by a panel of judges according to cleanliness (Figure 17), those with less stringy appearance were perceived as cleaner. The clinging together of fibers is an important criterion for measuring hair cleanliness. Although no similar measurements correlating light reflectance (luster) and hair

CLEANING OF HAIR 453 2OO 4*, ...... 4•, Right side: D.H. Left side: V.G.H. o •o •o •o 80 •6o Time after shampoo (h) Figure 15. Interfibrillar hair spacing as a function of time elapsed after shampooing. DH--hair washed with shampoo for dry hair VGH--hair washed with shampoo for very oily hair. (Reproduced with permission from ref. 9)- Figure 16. Photograph of clean hair tresses and of tresses soiled with artificial sebum (10% in hexane).