CONDITIONERS AND HAIR FIBER HARDNESS 585 0.5 1.0 1,5 0.500 pM/div 500.000 0,5 1,0 1.5 X 0.500 pM/div • 500.000 riM/Sir b Figure 3. "Real-time" 3-D height images of nano-indents on the "scale faces" of the same hair fiber (a) before and (b) after conditioner-treatment. (3-D height images: scan size = 2 t•m scan rate = 1.001 Hz number of samples = 256 data scale = 500 nm.)

586 JOURNAL OF COSMETIC SCIENCE • nM Suroeace distance Hori= distance Ueet distance •ngle Su•oeace distance Hoeiz distance Uevt distance Angle 191,35 nM 179. $9 nM 49 397 nM 4• ...... 15.371 de9 307.47 nM Z9S. 88 n• 47. 744 n'n •- 9.13S aeg Figure 4. a: Profile scan with the corresponding "real-time" height images of nano-indents on the "scale faces" of the untreated hair fiber. b (facing page): Profile scan with the corresponding "real-time" height images of nano-indents on the "scale faces" of the conditioner-treated hair fiber. 4.2 x 10 -9, which indicates that these are two independent measurement rows at 99.99% probability. CONCLUSIONS These investigations show that AFM measurements with the nano-indentation tech- nique are capable of distinguishing between the hardness of the scale faces of untreated and conditioner-treated hair fibers. This technique is useful in establishing conditioner- induced modifications in micromechanical properties (hardening or softening) of the hair fiber surface. Multiple indentations were made on the surface cuticle cells of a larger number of the same hair fibers before and aj%r multiple applications of the conditioner. Making measurements on the same hair fibers before and after multiple conditioner treatments