UV DAMAGE ON GRAY HAIR 105 eters were measured and used to determine the extent of hair damage and assess the relative effectiveness of the two UV filters in sun protection: hair color change, tryp- tophan damage, tensile strength, wet combing force, dynamic advancing contact angle, cuticle abrasion, and fiber swelling. MATERIALS AND TEST METHODS CHEMICALS The following chemicals were used: a. Octylmethoxycinnamate (OMC), Escalol 557, ISP Van Dyk Inc., Belleville, NJ b. Cinnamidopropyltrimonium chloride (CATC), Incroquat UV-283, Croda Inc., Par- sippany, NJ c. Ammonium laureth sulfate (ALS), Standapol EA-2, Henkel Corp., Hoboken, NJ d. Sodium lauryl sulfate (SLS), Standapol WAQ-SP, Henkel Corp., Hoboken, NJ HAIR SAMPLES Virgin dark brown and 90% natural gray hairs were purchased from International Hair Importers & Products Inc., Bellerose, NY. Four tresses each (about 3 grams) of natural gray and virgin brown hair were used for the UV study. Hair samples were also collected from the heads of four graying individuals (with no known history of chemical treat- ments). These hair fibers were separated manually into pigmented (black) and non- pigmented (gray) fibers for evaluations and comparisons to each other. TREATMENT OF HAIR SAMPLES Test hair tresses were washed with 5% ALS solution (hair/solution weight ratio -- 1/10) for three minutes and rinsed thoroughly under running tap water (-20øC) for three minutes at an approximate flow rate of 75 ml/sec. The tresses were then air-dried and labeled as tresses 1-4. Tress 1 was used as a control without any UV exposure. Tresses 2, 3, and 4 were treated with 10% SLS aqueous solutions containing 2% CATC, 2% OMC, and no sunscreen active, respectively. Tresses 2, 3, and 4 were soaked in their respective formulations for five minutes at 35øC at the start, and then every 24 hours thereafter. Following each treatment, the tresses were rinsed under running tap water (-20øC) for 30 seconds at the flow rate of about 75 ml/sec and then returned to an environmentally controlled chamber for further UV irradiation. IRRADIATION OF HAIR Four UV-B lamps (F20T12, Atlantic Ultraviolet Corp., Hauppauge, NY) were installed in an environmentally controlled chamber, which was set at a constant temperature of 27øC and a constant relative humidity of 65%. The hair tresses were positioned 10 cm from the UV lamps. Irradiation energies were determined using PMA UV-B and UV-A detectors (Solar Light Co. Inc., Philadelphia). The applied wavelength range and irra- diance were 280-320 nm, 0.14 mW/cm 2 for UV-B and 320-400 nm, 0.49 mW/cm 2 for

106 JOURNAL OF COSMETIC SCIENCE UV-A, respectively. The hair tresses were rotated constantly to assure uniform exposure to the UV irradiation. On days 3, 7, 15, and 20, fifty fibers from each hair tress were collected for evaluation. HAIR COLOR Computer images of the four test hair tresses were taken after UV irradiation and used to assess changes in color by naked eyes. The color of the treated samples, tresses 2, 3, and 4, was viewed and compared to the color of tress 1, the control without UV exposure. The color of the hair tresses was also measured analytically with a LabScan XE spectrophotometer (Hunter Laboratories, Virginia). The changes in color before and after UV irradiation for each tress were expressed as the total difference in color (DE), difference in light index (DL), difference in blue-yellowing index (Db), and difference in yellowing index (DYI) using the CIEL*a*b* system. HAIR DIAMETERS AND CROSS-SECTIONAL AREA A laser-scanning micrometer (Mitutoyo, LSM-5000) was used to measure the diameters and the cross-sectional areas at the middle section of each fiber. This instrument employs a 1.0-mw 670-nm wavelength laser. The micrometer was calibrated using standard calibration wires of known cross-sectional area. Test hair fiber samples for the laser- scanning micrometer were 3.0 cm in length and prepared using a metal-tube sample mounting system supplied by Dia-Stron Limited, UK. After measuring the cross- sectional area, test samples were transferred to the autosampler attached to a miniature tensile tester (MTT-670, Dia-Stron Ltd, UK) for tensile strength measurements. TENSILE STRENGTH The breakage resistance of single fibers was measured using a Dia-Stron MTT-670 attached to an autosampler in an environmentally controlled chamber at a constant temperature of 23øC and a relative humidity of 50%. The cross-sectional area data of each tested hair fiber was imported into MTTWIN software for automatic calculation of Young's modulus of each single fiber. The original cross-sectional area of each hair fiber was also used to calculate the contracted cross-sectional area at its break extension (strain-to-break). Then the revised cross-sectional area at the strain-to-break was used to calculate the stress-to-break. The average values of these parameters were calculated for 15 fibers randomly collected from each hair tress. WET COMBING FORCE The wet combing forces (peak load and total work) of test hair tresses were determined using a Dia-Stron MTT-160 at room temperature. Each test hair tress had a length of 18 cm. MTT operational parameters were set to the following: hair sample size of 30 mm force range of 2000 gram and combing speed of 120 mm/min. Five combing trials for each tress were conducted to calculate the average value. The percent changes in wet combing forces were calculated using the control value of the same hair tress before UV irradiation.