SURFACTANT INTERACTIONS 277 Table X Deposition From Shampoo Cleaning of Commercial Conditioner: Radiotracer Measurements • Treatment 2 SAC per gram wool (mg) TEALS per gram wool (mg) Total deposit 3 Conditioner A 3.17 (0.19) -- 3.17 (0.19) Shampoo B 4 1.37 (0.10) 1.37 (0.10) Cond. A/Shampoo B 1.66 (0.25) 3.09 (0.52) 3.28 (0.59) • Numbers in parentheses are standard deviations. 2 0.15 ml of each treatment was applied. 3 Total deposit for the conditioner/shampoo treatment was calculated by summing the SAC and TEALS and subtracting the TEALS deposits on clean wool. 4 This is a TEALS-containing commercial shampoo. was observed with repeated treatment, indicating that, unlike ALS, SDES-3 does not build up on conditioner-treated swatches. Table X shows the results of experiments in which shampoo B, a TEALS-containing commercial shampoo, was used to wash conditioner A-treated swatches. As was the case with SAC and TEALS alone, the shampoo exhibited increased deposition in the presence of conditioner as a result of SAC/TEALS complex formation. Because of this increased deposition, no net cleaning was observed: the total deposits before and after shampooing were comparable. This indicates that for fully formulated commercial products as well as for the active ingredients, formation of insoluble complexes between cationic condi- tioners and anionic detergents can occur on hair. CONCLUSIONS In this paper, light-scattering measurements, supplemented by radiotracer techniques, were used to demonstrate the formation on hair surfaces of dulling, insoluble complexes between common conditioner actives and the lauryl and laureth sulfate detergents used in virtually all commercial shampoos. Washing deposited conditioner active with the above C12 detergents was shown to result in little net cleaning as a result of buildup of both conditioner and detergent on the hair surface. Detergents with hydrophobic chain lengths less than 12 were shown to be superior to laureth sulfates in cleaning conditioner because of the absence of complex formation and also because of their ability to solubilize any previously formed complex. In the case of commercial conditioners, buildup was observed only from C 12 detergents, rather than from detergent and conditioner. This led to less dulling however, enough increased deposition from detergent was observed to occur, to again lead to little net cleaning by commercial shampoos. The above-documented buildup from conditioning, shampoo cycles could be a contrib- uting factor to the common consumer belief that the cleaning effectiveness of any particular shampoo decreases over time. A better understanding of the possible causes for decreases in cleaning with repeated use, such as the interactions documented in the present work, could result in products that would command more consumer loyalty.

278 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS ACKNOWLEDGMENTS We wish to thank Mr. Andrew Charig, who synthesized most of the radiolabeled materials used in this work. We wish also to thank Ms. Donna Hartnett, who synthe- sized [35SISDES-3. The bulk of the tress studies were performed by Ms. Donna Hartnett and Ms. Judy McKendrick. Ms. Hartnett and Ms. Lois Castrovince performed most of the radiotracer measurements. We are grateful to Mr. Frank Schebece for valuable discussions. REFERENCES (1) C. Reich and C. R. Robbins, Light-scattering and shine measurements of human hair: A sensitive probe of the hair surface, J. Sac. Cosmet. Chem., 44, 221-234 (1993). (2) C. Robbins, C. Reich, and J. Clarke, Dyestaining and the removal of cationics from keratin: The structure and the influence of the washing anion, J. Sac. Cosmet. Chem., 40, 205-214 (1989). (3) R. F. Stamm, M. L. Garcia, and J. J. Fuchs, The optical properties of human hair. I. Fundamental considerations and goniophotometer curves, J. Sac. Cosmet. Chem., 28, 571-599 (1977). (4) B. J. Tighe, "Subjective and Objective Assessment of Surfaces," in Polymer Surfaces, D. T. Clark and W. J. Feast, Eds. (John Wiley & Sons, Chichester, 1978), pp. 269-286. (5) D. B. Judd and G. Wyszecki, Color in Business, Science, and Industry, 2nd ed. (John Wiley & Sons, New York, 1963), p. 381. (6) C. Reich and R. Heck, unpublished results.