456 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Fluid Waxy Relation Between Quantitative and Qualitative Parameters. I 0 I I I o o ODD DO D DO0 OD DO \ o o D D D DD I I I I 0.5 1.0 1.5 2.0 Weight of sebum per head ,g Figure 20. Subjective perception of oiliness as a function of two quantities: the amount of lipid on the hair and •36, a quantity characteristic of the sebum fluidity (Reproduced with permission from refo 29). Distribution of Positional Isomers Dry Sebum ' C14 I i C•5 I C•6 . IIi I I I I C17 C18 Oily Sebum _I..L i ,1 , Ill ,IJ ,1 i i i I I 46 68 468 6810 ,I, Figure 21. Example of distribution of positional isomers of sebum acids for two characteristic subjects. (a) Subject with dry hair (b) subject with oily hair (Reproduced with permission from ref. 30).

CLEANING OF HAIR 457 determining the consistency of sebum and, through it, the perception of cleanliness of hair. V. CONCLUSIONS Although the essential features of detergency play an important role in the cleansing of hair, the processes that are important in determining the achievement of clean hair under practical conditions are very different from those that play a dominant role in the laundering of fabrics. A number of important gaps still exist in our knowledge about the mechanisms of cleaning of hair. Among these are the physico-chemical processes of sebum aging and its effects on the rheological properties of the soil the effect that particulate soil from the environment has on the fluidity of sebum the kinetics of removal of semi-solid soils from hair surfaces the relative importance of hair surface energy and of surface roughness in the resoiling of hair the contributions of various visual and tactile perceptions on the assessment of hair cleanliness and the psychophysical relationships between the magnitudes of perceived attributes on the one hand, and the physical properties of sebum and of the hair surface on the other. Answers to some of these questions, no doubt, will help the development of better hair cleaning procedures and products. REFERENCES (1) R. D. B. Fraser, T. P. McRae and G. E. Rogers, Keratins, their composition structure and biosynthesis (Charles C. Thomas, Springfield, Ill., 1972). (2) A.M. Kligman and W. D. Shelley, An investigation of the biology of the human sebaceous gland, J. Invest. Dermatol. 30, 99 (1958). (3) W. J. Cunliffe, W. D. Perera, P. Thackeray, M. Williams, R. A. Foster and S. M. Williams, Pilo-sebaceous duct physiology, Brit. J. Dermatol. 95, 153 (1975). (4) W. L. Cunliffe and S. Shuster, The rate of sebum excretion in man, Brit. J. Dermatol. 81,697 (1969). (5) M. Gloor, Determination and analysis of skin and hair, in Cosmetic Science, Vol. 1, M. Breuer, Ed., (Academic Press, New York, 1978) p. 218. (6) J. Solan (unpublished results). (7) M. Gloor, J. Rietkotter and H. C. Friederich, The deoiling and reoiling of the scalp and of hair after washing with different surfactants, Fette Seifen Anstreichmittel, 75, 200 (1973). M. Gloor, A. Schemel and H. C. Friedrich, The effect of hair dryers and hairsprays on the reoiling of hair after hairwashing, Kosmetologie, 3, 193 (1975). M. Leduc, D. Maes, J. M. Nadvornik, J. A. Reinstein, B. A. Turek and V. Vieu, Proc. loth I.F.S.C.C. Cong. (Melbourne, Australia, 1978) p. 693. H. T. Behrman, The Scalp in Health and Disease (C. V. Mosby Co., St. Louis, 1952) p. 32. E. M. Cottington, R. H. Kissinger and W. S. Tolgyesi, Observations on female scalp hair population distributions and diameters,J. Soc. Cosmet. Chem. 28, 219 (1977). W. L. Cunliffe, W. D. H. Perera, D. Thackeray, M. Williams, R. A. Foster and S. M. Williams, Pilo-sebaceous duct physiology, Brit. J. Dermatol. 95, 153 (1976). M. Gloor, J. Weidemann and H. C. Friederich, The influence of hair length on the excretion of the sebaceous gland in the scalp, Dermatologische Monatschrift, 160, 730 (1974). K. V. Curry and S. Golding, Hair lipids. I. Extraction of fatty materials from hair clippings, J. Soc. Cosmet. Chem., 22, 681 (1971). V. Valkovic, Trace Elements in Human Hair (Garland STPM Press, New York, 1977). M. Gloor, H.Joseph and H. C. Friederich, The paraffin content of skin surface lipids, Arch. Dermatol. Res., 250, 277 (1974). P. McMahon, J. Solan and M. Breuer (unpublished results). (8) (9) (10) (11) (12) (13) (14) (15) (16) (17)