350 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table II Shampoo and Conditioner Formulations Shampoo Conditioner Ingredient % Ingredient % ALS 12.0 Cetyl alcohol 3.5 CDEA 4.0 Germ II 0.5 Germ II 0.5 CTAC 0.5 NaH2PO 4 0.3 DI H20 q.s. DI H20 q.s. (Conditioner base 358-2A) (Shampoo base 358-1A) Ten cycles of the assigned grooming sequence were applied to each hair swatch as shown in Table II. The order of swatches was randomly assigned and changed for each groom- ing cycle. The initial wetting of swatches was done in 100 ml beakers, and the samples were segregated by type so that shampoo or conditioner residues did not contact "combed only" samples. The comb was rinsed thoroughly between uses. Hair swatches were dried in air and evaluated using various techniques that will be described. EVALUATION METHODS The changes caused by bleaching, perming, and grooming were evaluated in terms of both surface and structural properties. Surface properties were evaluated by microfluo- rometry and SEM, and surface wettability by the Wilhelmy balance method. The structural or bulk properties evaluated were dye diffusion, amino acid composition (especially cysteic acid content), mechanical properties, and fatigue behavior. Surface evaluations Microfiuorometry. Bleached hair samples were treated for ten minutes at room tempera- ture in a 0.005% aqueous Rhodamine B solution brought to pH 3.3 with acetic acid, then rinsed for three seconds in distilled water. For the grooming studies, a treatment time of 90 seconds was used. Cross-sectional and longitudinal microfluorometric studies were carried out using a Leitz MPV 1.1 microspectrophotometer with a PLOEMOPAK attachment. The PLOEMO- PAK attachment contains filter blocks dedicated to various narrow and wide band ranges specific for excitation of molecules fluorescing at various wavelengths. Scanning electron microscopy. A JSM-2 instrument (JOEL Company) was used for the determination of surface features. The samples were gold-coated to a thickness of ap- proximately 80-100 it. Wettability. The Wilhelmy balance technique (8) was used to determine single-fiber wettability. A Cahn D200 microbalance was used, with water as the wetting liquid. The wettability scans were made in the with-scale direction, and 3 mm of the fiber surface were scanned at a speed of 3 Ixm/sec. Fiber perimeters were determined by measuring wetting behavior in hexadecane.

EVALUATION OF HAIR DAMAGE 351 Evaluation of fiber structure Dye diffusion studies. The diffusion behavior of a fluorescent dye into hair fiber cross sections was measured using microfluorometry. The samples were treated for 3-5.5 hours at 50øC in 0.1% uranin solution, rinsed, dried, embedded and cured, microtomed to 10 •m thickness, and scanned cross-sectionally at a wavelength of 540 nm, using an excitation wavelength range of 450-495 nm. Amino acid analysis. The amino acid analysis was performed by Wella, AG, Darmstadt, on the untreated and bleached samples prepared at TRI/Princeton. Hair samples were hydrolyzed with 6 N HCI at 110øC for 24 hours. After multiple evaporations to dryness until the solution became neutral, a 5 •1 aliquot was withdrawn for derivatization. A pre-column derivatization method reported by Bidlingmeyer et al. (9) was used. A 5 aliquot was finally injected into the chromatograph. A programmed elution procedure with variable mixtures was used for optimum separation. Mechanicalproperties. Wet mechanical properties of single fibers were determined with an Instron tensile tester at a rate of extension of 40% per minute. Cross-sectional areas were assessed by use of an electronic vibroscope. Fatigue behavior. Constant load fatiguing was carried out on an apparatus that accom- modates 40 fibers in an impact-loading mode of fatiguing. The fatigue apparatus was described by Kamath et al. (10). Each 3 cm long fiber is mounted on a hook that is adjustable for fiber creep during the fatiguing procedure. A weight of 40 g is attached to the lower end of the fiber. The lower platform oscillates at approximately one cycle per second, and the fibers were fatigued for 100,000 cycles at 65% RH and 2 IøC. The weights mounted on the fibers clear the lower platform at its lowest position, thereby impact-loading the fibers. Each of the 40 positions has a microswitch counter that stops when the fiber fails. The conditions were the same for the bleached, permed, and groomed hair studies. A sample size of 60 replicates was used in each case. This type of fatiguing is known as constant load fatiguing rather than constant strain fatiguing. Strain levels in these measurements were well within the Hookean range. RESULTS AND DISCUSSION PRIMARY DAMAGE IN BLEACHED AND PERMED HAIR Surface changes Fiber surfaces of bleached hair were studied by microfluorometry and SEM. Wettability measurements were made on bleached hair and also on permed samples. Microfluorometry. Previous work with the fluorescent tracer Rhodamine B (CI Basic Violet 10) suggested that this compound would be suitable for exploring aspects of oxidative damage of the fiber surface and the cuticular region. Rhodamine B is a cationic dye that would be expected to show interactions with the sulfonic acid groups produced by oxidative treatments of hair the dye structure is shown in Figure 1. Longitudinal views of characteristic filaments of the four bleach treatments with Rhodamine B are shown in Figure 2. Rhodamine B deposited at the scale edges of unbleached hair (Figure 2a), with the possibility of some slight penetration into either the endocuticle or the intercuticular cell membrane. Oxidation for one hour (Figure 2b)