438 JOURNAL OF COSMETIC SCIENCE light specular reflection of a sample as compared with a standard (3,4). The decrease in surface roughness has direct influence on gloss. Sauremann et al. (5) observed that the hair roughness set by the cuticles can be increased with their deterioration or reduced by shampooing. Studies using transmission electron microscopy showed that consecutive shampooing cycles extract small amounts of proteins from the endocuticle, leaving empty spaces (holes) (6,7,9). Shampoos can also dissolve structural lipids and proteinaceous material from the cell membrane complex (8). Other treatments such as brushing, combing, and towel drying also damage the cuticles, and can generate holes in the endocuticle, rupturing and detaching the external cuticles, until the ends split. We have shown that these types of damage promote changes in human hair lightness (9). MATERIALS AND METHODS HAIR SAMPLES Tresses of virgin dark-brown hair, each weighing 2.0 g and approximately 15 cm in length, were used throughout. The hair samples were aligned from root to tip end and tied near the root end. Some of them were cleansed by 8-h extraction with ethyl ether in a Soxhlet, dried at room temperature, combed, and stored in a black desiccator prior to the treatments. DIFFUSE REFLECTANCE SPECTROPHOTOMETRY The diffuse reflectance measurements were performed using a Macbeth © Color-Eye © 2020 diffuse reflectance spectrophotometer. The instrument operation conditions were: (a) configuration CRIIS (C: white ceramic calibration, R: reflectance, I: ultraviolet waves included, I: specular component included, S: short viewing aperture) (b) D65 illumi- nant and (c) internal reference. The operation and the measurement conditions for human hair were established in a previous work (10). Spectra provided values of coor- dinates L* (color lightness), a* (redness if positive, or greenness if negative), and b* (yellowness if positive, or blueness if negative) from the CIELAB system of equations. From these, the color difference parameters, DL* (lightness difference), Da* (red-green difference), Db* (yellow-blue difference), and DE* (total color difference) were calcu- lated. Measurement error in total color difference was about DE* = 0.1, and hair sample variability dispersion was about DE* = 1.0. Measurements were done, keeping the same sample region and turning the hair sample in the instrument sample holder. The internal reference is one chosen measurement of this set that is closest to the average values for the set. Ten diffuse reflectance measurements were done in each tress, and the values of the color parameters shown in the tables are arithmetic averages and estimated standard deviations of these sets. LIGHT MICROSCOPY Ten hair fibers 6-cm long were positioned side by side in glass slides. Root and tip regions were observed under white light in a bright field using a Leica MZ 12.5 stereo

EFFECT OF DYEING AND HEAT ON HAIR COLOR 439 microscope. Observations were registered in TMAX ISO 100 Kodak film, rendering a set of 80 photomicrographs. PERMANENT DYEING Six commercial permanent dyeing formulations from L'Oreal Paris were used, three long-lasting formulations (Imedia Excellance Cr6me, containing ammonia and hydrogen peroxide) and three tone-up formulations (Casting, ammonia free, and low hydrogen peroxide). For each long-lasting formulation, a similar color of tone-up formulation was chosen. The formulations were of black, blond, and red colors. Each dye was applied to two tresses, following the enclosed instructions. All procedures were done using gloves and after wetting the hair. The long-lasting formulation was left acting for 40 min, and the tone-up formulation was left acting for 20 min. After this time, the tresses were washed in warm water and dried at room temperature. The virgin hair tresses were dyed three successive times to attain color saturation DRS measurements were taken after each dyeing cycle. After the three dyeing cycles, each tress was submitted to six se- quential shampooing washes. A commercial L'Oreal shampoo formulation particularly indicated for dyed hair was used. To each wetted tress, 1 ml of shampoo was applied with gloves and rubbed in for 5 min the tress was washed out in tap water and dried at room temperature. DRS measurements were taken after each shampooing cycle. EFFECT OF EXPOSURE TO A HOT PLATE A Taiff • professional hot plate was used. The working temperature was 172øC, as measured by a thermocouple. Two virgin hair tresses were used. The hot plate was applied as follows: each hair tress was exposed to the plate for 15 s and then cooled for 10 s, four times. This gives a 1-min exposure time. The tresses were then washed with distilled water for 20 s and dried with a hand dryer for approximately 7 min. This treatment was repeated up to a 10-min exposure to the hot plate. DRS measurements were done after each 1-min exposure. The silicone treatment was done in two tresses previously washed with distilled water. To each tress, 2 ml of product was applied, being manually distributed from the root to the tip end of the tress. These tresses, dried at room temperature, were submitted to the same hot-plate exposure treatment of the untreated hair tresses. The silicone used was Dow Corning 1501 fluid, a cosmetic ingredient recommended for renewing hair split ends. The product data sheet specifies that it contains cyclopentasiloxane and dimethiconol. EXPOSURE TO DRYER HEAT A Brittania 1300W dryer was used. The average working temperature was 62øC, as measured by a thermocouple. A virgin hair tress was attached to a wood holder using cotton yarns. The dryer was positioned in front of the tress, at middle height, keeping a distance of 6 cm between the tress and the dryer. The tress was exposed for 10 min in five cycles, at 20-min intervals. After 12 h at room temperature, the same hair tress was continuously exposed to the dryer for 60 min and DRS measurements were taken. Fibers were collected from the virgin hair tress before (control) and after the heat treatments for light microscopy observations.