J. Cosmet. Sci., 66, 379–409 (November/December 2015) 379 Quantifying hair shape and hair damage induced during reshaping of hair ROGER L. MCMULLEN, GUOJIN ZHANG, and TIMOTHY GILLECE, Ashland, Inc., Bridgewater, NJ 08807. Accepted for publication September 14, 2015. Synopsis The manipulation of hair shape, either to straighten or curl hair, is carried out on a grand scale in the hair care consumer market. Often, such changes are brought about through chemical or physical treatment, resulting in changes to hair chemistry. In this article, we review existing and present new data on methods to assess the effi cacy of such treatments, mostly concentrating on imaging technologies used in conjunction with image analysis. In addition, we introduce spectroscopic imaging techniques and fl uorescence spectrophotometry as tools to assess the biochemical state of the hair fi ber as a result of hair shape modifi cation regimens. Finally, we demonstrate how the structural integrity of the fi ber is monitored with dynamic scanning calorimetry and traditional mechanical testing of the tensile properties of hair. INTRODUCTION As an outward expression of beauty, individuals often manipulate the shape of their hair to make themselves more attractive. Often, this involves subjecting hair to chemical and physical treatments that are carried out to change the shape of hair, such as permanent waving, relaxing, and hair straightening treatments (e.g., hot fl at iron, Brazilian hair treatments, and Japanese straightening). Although permanent waving may be more of a niche market, relaxers are used almost universally by individuals with African hair, espe- cially in the United States (1). In recent years, the use of hot straight irons and Brazilian hair treatments (e.g., Brazilian Blowout) has exploded (2). In order to gain a better grasp of the effi cacy of products and treatments, it is desirable to have established techniques to quantify such changes in the three-dimensional geometry of the hair fi ber assembly. One of the most suitable avenues for carrying out such analyses involves photographic imag- ing in combination with image analysis techniques (3). In most circumstances, these modifi cations to hair are accompanied by irreversible damage to the fi ber’s chemical and morphological structure. For example, thermal treatments carried out with hot irons can result in a loss of free and bound H2O, tryptophan degradation, color changes, increases in mechanical combing forces, cuticle cracking (axial and radial), cuticle fusion and Address all correspondence to Roger McMullen at rmcmullen@ashland.com.