QUANTITATIVE CHARACTERIZATION OF COMBING FORCE 781 mined by studying tresses placed in both swelling and nonswelling liq- uids. However, the 14% volume increase caused by water is probably not responsible for more than, at most, a small percentage of the in- creased combing force of wet hair (Table I), for the combing force of a wet tress weighing 2.75 g is found to be greater than that of a dry tress weighing nearly twice as much (Table III ). b) It is obvious, even to the casual observer, that the strands of hair in a wet tress tend to cling together, so much so that it is often somewhat difficult to separate a single strand from the others. The amount of force necessary to overcome this interaction by the comb teeth must be a part of the higher wet combing force. Other, as yet unknown, interactions are also probably involved. The effects of quaternary ammonium compounds containing one or two long alkyl chains that are discussed in this report have long been known and these materials have been widely used to soften textile fibers and fabrics dur- ing processing and washing and to condition hair after shampooing (11-13). A great deal is known about the rate and mechanism of sorption of these ma- terials onto hair and textiles (14). Much has also been learned about the sur- face structure of keratin fibers and the effect of this structure upon their prop- erties (1, 2). Nevertheless, at present, there is no complete picture of the mechanism of the conditioning process and of how these materials so dramati- cally affect the "feel" and combing properties of hair. In 1971, Finkelstein and Laden described an investigation of the effect of various hair conditioners on the ease of combing (evaluated subjectively) when used both above and below the critical micelle concentration (15). They studied the effect of chain length of cationic used and interpreted their results in terms of surface adsorption of the conditioner and the formation of two-dimensional "hemi-micelles" on the hair surface. To the best of our knowl- edge, no further investigations developing upon these results have been re- ported. It is hoped that future studies, using the procedure described in this report and/or the many techniques now available for studying fiber friction and sur- face properties (including scanning electron microscopy), will elucidate the nature of the conditioning process. (Received December 22, 1972) REFERENCES (1) Makinson, K. R., Some observations on the effects of mild shrinkproofing treatments in wool fibers, Text. Res. J., 38, 831-42 (1968). (2) Hepworth, A., et al., The surface topography of chemically treated wool fibers, J. Text. Inst., 60, 513-46 (1969). (3) Wolfram, L. J., and Lindemann, M. K. O., Some observations on the hair cuticle, J. Soc. Cosmet. Chem., 22, 839-50 (1971). (4) Schwartz, A.M., and Knowles, Jr., D.C., Frictional effects in human hair, Ibid., 14, 455-63 (1963.)

782 (5) (6) •7) (9/ (10) (11) (1•,) (13) (14) (15) JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Nagai, T., Sukuma, K., and Tanknori, S., Hair shampoo evaluation, Soap Chem. Spec., 39-42, 95 (April, 1966). Waggoner, W. G., and Scott, G. V., Instrumental method for the determination of hair raspiness, J. Soc. Cosmet. Chem., 17, 171-9 (1966). Collins, J. D., and Chaikin, M., The stress-strain behavior of dimensionally and strut- rurally non-uniform wool fibers in water, Text. Res. J., 35 777-87 (1965). Breuer, M. M., The binding of small molecules to hair. I. The hydration of hair and the effect of water on the mechanical properties of hair, J. Soc. Cosmet. Chem., 23, 447-70 (1972). Alexander, P., Hudson, R. F., and Earland, C., Wool, Its Chemistry and Physics, 2nd Ed., Franklin Publishing Co., Inc., N.J., 1963. Chamberlain, N.H., and Speakman, J. B., Uber hysteresisersheinungen in der wasser- aufnahme des menchenhaares, Z. Electrochem., 37, 374-5 (1931). Evans, W. P., Cationic fabric softeners, Chem. Ind. (London), 27, '893-903 (1969). Cohen, S., in Patterson, E. Scott, Fatty Acids and Their Industrial Applications, Mar- cel Dekker, Inc., New York City, 1968, pp. 250-7. Kluge, A., Properties of quaternary ammonium salts-their use in cosmetic and hair treatment preparations, Amer. Per[urn. Cosmet., 81, 35-40 (March, 1966). Scott, C. V., Robbins, C. R., .and Barnhurst, J. D., Sorption of quaternary ammonium surfactants by human hair, J. Soc. Cosmet. Chem., 20, 135-52 (1969). Finkelste•n, P., and Laden, K., The mechanism of conditioning of hair with alkyl quat- ernary ammonium compounds, Proc. IV Int. Wool Text. Res. Con[. Part I, John Wiley and Sons, New York, 1971, pp. 673-80.