256 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS aging as the hair grows away from the scalp over time, and the degree of UV exposure. Deterioration in hair's physical properties occurs more from aging during growth of the shaft and UV exposure than from chronological aging of the test subject. In our tests, changes in tensile strength, low stress extensibility, and the ability to hold water at low humidity paralleled each other. While changes in tensile strength should reflect disul- fide bond deterioration and cortex properties, changes in water retention and low force extension should reflect cuticle properties. Hair from swatches treated singly in vitro or in vivo from subjects using a lipid- containing shampoo and conditioner over a four-week period responded favorably. Ap- plication of a biological lipid complex that mimics the lipids found in healthy hair cuticles resulted in improvements in all three parameters tested. Evaluation of hair body Y. K. KAMATH and H.-D. WEIGMANN, TRI/Princeton, P.O. Box 625, Princeton, NJ 08542. INTRODUCTION Hair body is a psychophysical attribute associated with the bulk and springiness of a hair mass, represented, respectively, by the visual and tactile properties of the hair assembly. Tolgyesi and co-workers (1) defined body as "... the ability of a hair mass to resist and recover from external deformation." Obviously, this definition is related to the tactile characteristics of a fiber assembly such as hair. The physical properties that enable a fiber assembly to resist both deformation and recovery from deformation are fiber modulus and interfiber adhesion, respectively. The typical action used by people in evaluating the springiness of a fiber assembly is one of either pressing or squeezing the assembly with the hand and observing the response, especially on releasing. It has often been conjectured whether these psychophysical characteristics can be pre- dicted from objective measurements in the laboratory. Such measurements will be useful in product developments as well in claim substantiation. With this in view, a radial compressibility method was developed at TRI for the interpretation of the tactile response of a fiber assembly. Mechanistically, it stimulated the squeezing of a hair tress by hand and observing the response. Since recovery from deformation depends on interfiber adhesion, a fiber pull-out method for determining this property was also developed. Following the method of multiple linear regression used by Kawabata (2) in the evaluation of "hand" of textile fabrics, an attempt has been made to predict hair body from the objective measurements described above. In parallel fashion, Garcia and Wolfram (3) have developed a ring compressibility

PREPRINTS OF THE 1996 ANNUAL SCIENTIFIC MEETING 257 method that also accomplishes radial compression in principle during the traversal of a hair tress through a ring of a given diameter. EXPERIMENTAL Ten tresses of European dark brown hair, each weighing 13 g (--9000 fibers) were prepared and cleaned by washing with a solution of 10% sodium lauryl sulfate, dried, and conditioned at 65% RH and 21øC. After the radial compressibility measurements on the untreated tresses, they were given different treatments to impart different levels of body. The tresses were numbered 1-10 in the order of increasing body. After measurement of radial compressibility, the tip end of the tresses were packed in a cylinder and cut to make fiber adhesion measurements by the pull-out method. RADIAL COMPRESSIBILITY The radial compressibility apparatus is shown in Figure 1. The top view of the split rings used in tress compression are shown in Figure 2. Even though the method is referred to as radial compressibility, it should be realized that the tress is compressed to an elliptical rather than a circular cross-section. In a typical experiment the tress was combed and fluffed and mounted in the compressibility apparatus. Energy for compres- sion (E•) between fixed initial and final tress dimensions was measured. After releasing, a second measurement of compression energy (E2) was made without disturbing the tress. From these data the following quantities were calculated: AE 2 = 100 (E2,• - E2,untr)/E2,untr and FAI = 100 (El,tr -- E2,tr)/El,tr It should be mentioned that FAI is related to interfiber adhesion. High interfiber adhesion will lead to lower compression energies in the second compression, as compared to that of the first, because the tress does not recover fully to its original dimension (E 2 El). _ • Horseshoe INSTR• CROSSHEAD Figure 1. Radial compressibility apparatus.