282 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS 60 50- 40- 30- 20- 10- FFA PW SC I CHOL SPW RESIDUE FRACTION CYCLE • 10 CYCLES • 20 CYCLES I AVG Figure 6. Effects of multiple soiling/shampooing treatments on average (by chemical fraction) sebum residues on hair. Hair soiled with 2% sebum solution and shampooed with 10% ALS. Soiling/shampooing carried through one, ten, and twenty cycles. FFA = average ofpalmitic, stearic, and oleic acid components PW = average of paraffin components SQ = squalene component CHOL = cholesterol component SPW = average of synthetic spermaceti wax components TG = average of triglyceride components AVG = average of all of the above fractions. These observations are explained by the fact that at the highly soiled tress levels, the bulk removal of sebum is most likely a rollback mechanism (5) in which surfactant solution comes in contact mainly with the sebum matrix. In this type ofsebum removal, principal effects are most likely liquid-liquid (detergent--sebum) in nature, with the actual surface effects of the hair playing only a minor role. As the soiling level decreases during the cleaning process, more of the hair surface is available for surfactant-sebum- substrate interactions. This results in a relatively constan't amount of fraction residue on the substrate. COMPARISON OF THE VARIOUS SURFACTANT SYSTEMS As previously mentioned, certain sebum fractions were more effectively removed from the hair tress than others. Component removal is manifested by two key observations for the single-cycle treatments: 1. The polar sebum fractions were more easily removed from the substrate than the nonpolar fractions. 2. The degree of non-polar fraction removed is determined by the surfactant. For every surfactant system studied, the most difficult fraction to remove appears to

EVALUATION OF SHAMPOO DETERGENCY 283 60 5O 4.0- ,50- 20- 10- FFA PW SQ CHOL RESIDUE FRACTION 17'7] 1 CYCLE • 10 CYCLES • 20 CYCLES SPW AVG Figure 7. Effects of multiple soiling/shampooing treatments on average (by chemical fraction) sebum residues on hair. Hair soiled with 2% sebum solution and shampooed with 10% AES. Soiling/shampooing carried through one, ten, and twenty cycles. FFA = average ofpalmitic, stearic, and oleic acid components PW = average of paraffin components SQ = squalene component CHOL = cholesterol component SPW = average of synthetic spermaceti wax components TG = average of triglyceride components AVG = average of all of the above fractions. be the paraffinic wax compounds illustrated in Figure 3. The easiest fraction to remove from the hair is the fatty acid components. All of the single-component surfactant systems investigated removed essentially the same amount of the free fatty acids from the sebum as seen in Figure 4. The actual residue level is normally below 5% relative to the amount originally applied. This same observation generally held true for the triglycerides with greater than 90% removal. Distinctions between surfactant systems became more apparent with the comparison of the removal of the cholesterol, paraffins, squalene, and spermaceti fractions. In every case AES removed more of each particular sebum fraction than ALS or AOS. The greatest difference is found for the paraffin fraction. AES had an average residue of 10% and the other two surfactants had average residues of 45 %. The difference between ALS and AOS was primarily manifested in the removal of the cholesterol fraction. The AOS removed 85% of this fraction, while the ALS removed only 65%. SHAMPOOING CYCLES One of the most interesting sets of questions posed by consumers is: 1. Does my shampoo become "tired" with regular use? 2. Do I need to regularly change shampoos to keep my hair clean?