CLEANING HAIR 319 Cycle Cycles lOO ß 60 o E • 40 20 o c 14 c 16 c 18:21 c 18 P.W. CHOL. EST. 8ebum Component Figure 5. Removal of sebum components by ALS for one and ten soil/wash cycles. detergency theory (10). Since these results are for a pure surfactant, more data are necessary to draw any conclusions for extrapolating to shampoos, since other ingredients that alter surfactant properties are used in shampoo formulations. For one soil/wash cycle, Thompson et al. conclude that the polar materials are more easily cleaned from hair than the non-polar, and that the degree to which the latter are removed is dependent on the surfactant. Our present data are in general agreement with these conclusions however, our data show that squalene does not build up after ten soil/wash cycles. We also concur that the paraffin waxes are the most difficult materials to remove (along with the spermaceti esters) and that SLES-2 is superior to ALS for cleaning lipid soils. The Thompson paper indicates the cholesterol fraction to be difficult to remove for one and 20 cycles. For ten cycles there is a dramatic increase from 65% to 85% removal, a value more consistent with our results showing that cholesterol is easily cleaned from hair. Squalene is present in the sebum used to soil the hair and appears in calibration chro- matograms of the sebum. However, after the extraction procedure it is not found in either control or washed tress extracts. The drying and extraction procedures are those reported (7), so it is not clear why no squalene is detected in practically any chromato- gram under either of our soil/wash conditions. Preliminary data does indicate some loss of squalene during the low-level heating to provide a uniform moisture content throughout the sample set. This heating may be enough to remove any squalene not cleaned off by the wash surfactant and thus may explain the absence of squalene in

320 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS extract chromatograms. One would expect, though, that if squalene is building up, this effect would be evident in our ten-cycle data even if much is vaporized after one cycle. However, there is no evidence of this, and we are at a loss to explain this anomaly between these and the Thompson data for the squalene component. In summary, our data show that for one soil/wash cycle, surfactants do selectively clean sebum components from hair at low concentrations. But, as a first approximation, the amount of sebum removed is a function of the detergency of the surfactant, and thus the difference between SLES-2 and ALS is primarily a function of the superior detergency of the former [as predicted by surfactant theory (10) SLES-2 has the lower cmc] rather than differences in selective cleaning. The non-polar sebaceous components (paraffin waxes, esters) are more difficult to remove than the more polar ones, but we contend that the overall surfactant detergency is the determining factor. For ten soil/wash cycles, we find that SLES-2 is superior, and a build-up is found on hair washed with ALS under both (a) the model conditions using 0.01% surfactant and bulk washing and (b) realistic conditions using 10% surfactant and handwashing. This we attribute to hard water/fatty acid interactions. We believe that the data of this paper provide suffi- cient evidence to warrant extended use testing of potential surfactant systems for oily soil detergency in the manner described. REFERENCES (1) M. Gloor, Determination and analysis of sebum on skin and hairs, Cosmet. Sci., 1, 217 (1978). (2) J. Koch, K. Aitzetmuller, G. B. Horf, and J Waibel, Hair lipids and their contribution to the perception of hair oiliness: Parts I and II, J. Soc. Cosmet. Chem., 33, 317- 343 (1982). (3) K. V. Curry and S. Golding, Hair lipids. I. The extraction of fatty materials from hair clippings, J. Soc. Cosmet. Chem., 22, 681 (1971). (4) A. W. Weitkamp, A.M. Smiljanic, and S. Rothman, The free fatty acids of human hair fat,J. Am. Oil Chem. Soc., 69, 1936 (1947). (5) D. A. Shaw, Hair lipid and surfactants. Extraction of lipid by surfactants and lack of effect of sham- pooing on rate of re-farting of hair, Int. J. Cosmet. Chem., 1, 291-302 (1979). (6) M. M. Breuer, Cleaning of hair, J. Soc. Cosmet. Chem., 32, 437-458 (1981). (7) D. Thompson, C. Lemaster, R. Allen, and J. Whittam, Evaluation of relative shampoo detergency, J. Soc. Cosmet. Chem., 36, 271-286 (1985). (8) W. G. Spangler, H. D. Cross, and B. R. Schaafsma, A laboratory method for testing laundry products for detergency, J. Amer. Oil Chem. Soc., 42, 723-727 (1965). (9) J. Clarke, Unpublished data. (10) Milton J. Rosen, Surfactants and Interfacial Phenomena, 2nd ed. (Wiley-Interscience, 1989), pp. 363-392.