Preface In 2006, the International Conference on Applied Hair Science was two years old and was still in its infancy. Like any two-year-old, it was learning and developing its own personality and strength. In terms of attendance as well as papers presented, the second conference was as good, or even a little better, than the first one. I want to thank all the participants and the presenters for contributing their time and talent to the conference as well as to the common good of the cosmetic industry as a whole. As was the case with the first conference, the papers of the 2006 conference were selected purely on the basis of their scientific content. However, it is difficult to make this judgment based on a relatively short abstract. Therefore, I would suggest that going forward we base the selection process on a two-page extended abstract of the presenta- tion. Although I have mentioned it in my opening and closing statements at the conference, I would like to reiterate that we should try to concentrate on the science of developing and testing the efficacy of new materials and commercial hair care products. I recognize that this process may be difficult and complicated in the case of plant-based actives, but it is important to make an attempt to establish the chemical nature of the true active rather than the "extract." Because of the limited number of papers, we could not divide them into specific sections. The order this time is somewhat broad, the first half dealing with physical methods and the second half dealing with raw materials and products and related chemistry. At future conferences, we may make an attempt to invite papers in specific areas of hair cosmetics. I thank all the participants for making this conference a success. I hope that the interest shown by the industry by way of sending their representatives and lending their spon- sorships to this conference will endure, and that the conference will expand its activities in the future to serve the industry in return. I thank the Society of Cosmetic Chemists for its support and for agreeing to publish these papers in the Journal of Cosmetic Science. We appreciate the help of volunteers from TRI/Princeton and especially thank Eleanor Lehman and Dina Walker for organizing this conference and making it a success. Vll YASH K. KAMATH Conference Chair TRI/Princeton

]. Cosmet. Sci.J 58, 269-282 Quly/August 2007) Patterns of light interference produced by damaged cuticle cells in human hair MANUEL GAMEZ-GARCIA and YUAN LU, Ciba Specialty Chemicals, Polymer Effect Research, 540 White Plains Road, Tarrytown, NY 10591-9005. Synopsis Colorful patterns of light interference have been observed to occur in human hair cuticle cells. The light interference phenomenon has been analyzed by optical microscopy. The strong patterns of light interference appeared only in cuticle cells that had been damaged either mechanically or by thermal stresses. Cuticle cells that were not damaged did not produce this phenomenon. The zones of light interference on the hair surface were seen to extend to cuticle sheath areas whose damage was not apparent when analyzed under the Scanning Electron Microscope. The presence of oils and other hydrophobic materials in the hair had a strong effect in the appearance or disappearance of the interference patterns. Furthermore, the gradual absorption and desorption of water by the cuticle cells altered the nominal area of the colorful patterns. This paper will attempt to explain the light interference phenomenon in the cuticle cells by means of the two following mechanisms: 1) Variation in the index of refraction of cuticle cell layers due to the appearance and coalescence of micro-voids which eventually lead to the partial or total separation of cuticle cells and 2) The interaction of white light with the micro-voids and de-cemented cuticle cells either by thin film interference or diffraction. INTRODUCTION The role of the cuticle sheath on the hair optical properties is paramount to its cosmetic appearance (1). For instance, shine in hair is related to the ratio of specular to diffuse light reflected from the epicuticle surface (2,4). The weak iridescence in hair contributes, on the other hand, to its natural and healthy appearance and is produced by weak colored patterns of light interference reflected by the thin film structure of virgin cuticle cells. Incidentally, it is worth mentioning that the bright color possessed by various insects and birds arises not from organic pigments but rather by a similar mechanism involving iridescence (5-8). Many beetles, butterflies, and also the feathers of various birds owe their bright colors to the phenomenon of iridescence. This phenomenon is produced by various coherent light scattering mechanisms involving light interference and diffraction as white light interacts with the ordered micro-structure present in the cell membranes of feathers and also in the skin of insects. Color in hair is not due to a phenomenon of iridescence but rather to the interaction of white light with melanin (1). Melanin acts as a pigment and as it will be discussed later the strong iridescence patterns appearing on damaged cuticle cells may be rather del- 269