ALIGNMENT CONTROL AND SOFTNESS CREATION IN HAIR 23 of their hair, was estimated. Several small unruly tresses, consisting of 150 hair fi bers each, collected from the virgin curly tress of a Japanese female, were attached to a force meter and the maximum loads achieved during fi nger combing and bunching of the tresses were measured these loads corresponded to the points where the tresses were just straightened and aligned. The maximum loads achieved were then converted to approxi- mate values of load per fi ber. STRESS RELAXATION MEASUREMENTS Stress relaxation measurements were carried out on a KES-G1-SH tensile tester (Kato Tech Co. Ltd., Kyoto, Japan) in the stress relaxation mode. Damaged curly hair samples of 60 mm in length were taken from the tip part and set individually in the removable clips of the instrument to give a test length of 50 mm. The test apparatus consisted of a 1000-ml glass beaker lined with two overlapping 150-mm-diameter fi lter papers (Whatman International Ltd., Maidstone, England). These papers were thoroughly wetted with deionized water dispensed from a squeezy bottle 30 min before the ex- periment was started. Deionized water (200 ml) was then maintained in the beaker at all times to ensure that the fi lter papers remained damp and to maintain a relative hu- midity of above 95% within the beaker. A two-piece lid was fabricated from thin plas- tic sheet so as to form a tight fi t around the arms of the tensile tester when in place. The beaker was raised around the sample area and the lid was carefully placed so as to form a tight fi t around the arms of the tensile tester, but without touching the moving sample arm. This arrangement kept the mounted fi ber centered in the beaker. The relative humidity conditions within the beaker apparatus were monitored with a Testo 635 handheld digital temperature and humidity probe (Testo AG, Lenzkirch, Germany). After an equilibration time of 5 min, a slight strain (typically 5% of the fi nal extended load) was applied to remove the crimp and straighten the sample. This equilibration time was also observed after the fi bers were treated with the relevant solutions. A strain of 0.5% was then applied to the sample at a rate of 0.01 mm s−1, and the stress relaxation was measured over a 20-min period. Data were collected via a personal computer and exported as a comma separated values (.csv) fi le that could be opened by any common spreadsheet and graphing software. Due to the small extensions used in these experiments, it was possible to test each sample before and after treatment, thereby lowering uncertainty and minimizing the sample numbers. It also negated the need to measure the fi ber diameters because the same fi ber could be followed throughout. It was assumed that the swelling of the fi ber due to the treatment was negligible. ASSESSMENT OF INITIAL MODULUS To obtain the initial modulus of hair in the low strain regions, stress versus strain mea- surements were carried out on a KES-G1-SH tensile tester (Kato Tech. Ltd., Kyoto, Japan) in the stress–strain mode. Measurements were performed on 50-mm-long hair under 20% relative humidity conditions, using a strain of 0.25% and a strain rate of 0.01 mm s−1.

JOURNAL OF COSMETIC SCIENCE 24 The same fi bers were tested before and after treatment for consistency. Data were exported in the .csv format for analysis in spreadsheet and graphing software. NANOINDENTATION AND FORCE MAPPING BY AFM Untreated virgin root, untreated damaged curly, control treatment–treated damaged curly, and GG treatment–treated damaged curly hair were set in parallel, at approxi- mately 1-mm spacing from each other, in a mold and embedded in Epon 812 resin. Five samples of each type were embedded. After curing, the blocks were removed from the mold, trimmed, and cut with a diamond knife to reveal mirror-fi nish cross sections of the hair. The parameters used for these measurements are given in Table II. The instruments used were Nanoscope V and Dimension 3100 (both Veeco Instruments Ltd., Santa Barbara, CA). Areas exhibiting components of the hair fi ber of interest [exocuticle, endocuticle, bulk cortex, and cortex cell membrane complex (CMC)] were selected, and measurements were performed on 4× 4 μm regions (at 64 × 64 pixels). The number of fi ber samples tested was between three and fi ve and, typically, around 20 force curves were obtained for each fi ber component ( 300 in the case of the bulk cortex). Values of the reduced Young’s modulus were then calculated using a simulation (10) adapted from the Hertz Model. All AFM measurements were performed under approximately constant conditions of 24°C and 50% RH. RESULTS AND DISCUSSION EFFECT OF DAMAGE ON ALIGNMENT AND SOFTNESS PERCEPTION The generation of unruly and irregular hair samples through common hair treatments is shown in Figure 1 an otherwise healthy tress (Figure 1A) subjected to the model damage process, consisting of a single perm treatment and bleached fi ve times (with 15 shampoo- ing and conditioning cycles after each step), becomes unruly, while individual hair fi bers adopt an irregular form that causes visual misalignment of the bundle (Figure 1B). Al- though misalignment from such damage may, in some cases, be attributed to the altered surface properties of the hair (11), the fact that individual fi bers adopt such irregular shapes must be related to some, as yet undetermined, internal changes. To elucidate how such irregular fi bers and misaligned hair bundles can affect the perception of softness, Table II AFM Experimental Parameters Parameter Setting Cantilever (TESP type), Spring constant, k 24.3 N m-1 Z-scan rate 1 Hz (600 nm s-1) Ramp size 300 nm Trigger defl ection 10–15 nm