j. Cosmet. Sci., 55, 437447 (September/October 2004) Hair color changes caused by dyeing and thermal treatments ANA CAROLINA SANTOS NOGUEIRA, CARLA SCANAVEZ, CRISTIANE CARNELOS, ALEXANDRE GASPARI, and INI•S JOEKES, Instituto de Qu/mica, Universidade Estadual de Campinas (UNICAMP), Caixa Postal 6154, 13084-971 Campinas, SP, Brazil. Accepted for publication August 26, 2004. Presented at the 22 " IFSCC Congress, Edinburgh, Scotland, September 2002. Synopsis The aim of this study was to show the effect of heat exposure, dyeing, and shampooing on hair color as measured by diffuse reflectance spectrophotometry. Successive dyeing of virgin hair with six permanent commercial formulations showed that color saturation was obtained after the first dyeing cycle. An unex- pectedly high difference in hair color saturation, measured as DE* values, was obtained for virgin hair samples that differed only in cleansing history. After six sequential washings of the dyed hair samples, no difference was observed in color durability, indicating that the adhesion strength is similar to long-lasting and tone-up dyeing formulations. Exposure to a hot plate at 172øC showed a significant darkening of the virgin hair samples after 2 min. On the other hand, virgin hair samples exposed to the gentler heat of a hand dryer (-60øC) showed partial disappearance of the hair medulla after 60 min. However, values of total color difference were near the error limit. INTRODUCTION Hair health is frequently related to its color and gloss. Hair color is attributed to the melanin granules present in the cortex (1). However, only a few papers are found in the literature involving hair color. This paper describes the color properties of hair as related to some simple cosmetic treatments. McMullen and Jachowicz (2) studied the effect of curling irons on hair color. Samples were submitted to a hot plate at 160øC for 30 min. Color analysis was done using the Hunter L*, a*, b* color coordinates. Significant color changes were observed, such as an increase in yellowness of white and Piedmont hair and yellowing and darkening of bleached hair. The most frequent gloss measurement is the specular gloss, which corresponds to the Address all correspondence to In•s Joekes. 437

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