j. Soc. Cosmet. Chem., 28, 139-150 (March 1977) The effect of fiber diameter on the cosmetic aspects of hair NALING E. YIN, ROY H. KISSINGER, WILLIAM S. TOLGYESI, and ELLYN M. COTTINGTON, Gillette Research Institute, 1413 Research Boulevard, Rockville, MD 20850. Received July 20, 1976. Presented 9th IFSCC Congress, June 1976, Boston, MA. Synopsis Most COSMETIC ASPECTS of a head of HAIR depend on the physical characteristics of the HAIR MASS. In turn, the hair mass characteristics are determined (directly or indirectly) by the properties of its individual FIBER COMPONENTS. Among fiber properties, diameter is of great significance. It influences hair body, tangling, combing, and resistance to damage. Both human hair and a model system using synthetic fibers were used to study the fiber diameter contribution. When these systems were assessed using combing, body, and abrasion test methods, it was found that the fiber diameter was directly related to hair body, combing ease, and abrasion resistance when all other hair or synthetic fiber properties were equal. INTRODUCTION Many of the important, consumer appreciated hair characteristics are based on the mechanical behavior of the fiber mass. The mechanical behavior, in turn, is determined by fiber properties and fiber-fiber interactions. Some of the most important fiber properties which influence the mass behavior are toodull, frictional characteristics, cross-sectional shape, longitudinal configuration and, last but not least, diameter. The present paper is concerned with the influence of fiber diameter on some cosmetic at- tributes of hair. Cross-sectional size of terminal scalp hair is subject to significant variations among dif- ferent population groups (1). For individuals, the mean diameter ranges from under 50 to about 90 •m, even in a relatively small sample of Caucasian adult population (2, 3). •39