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?

284 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS 6O 5O 4O • 3o 2o 10 o FFA PW SQ CHOL SPW TG AVG RESIDUE FRACTION • 1 CYCLE • 10 CYCLES • 20 CYCLES Figure 8. 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% AOS. 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. The question we decided to address was: Is there a difference in the amount of total sebum or sebum fraction left on the hair between the 1st and the nth soil/shampoo cycle? In an attempt to analyze sebum removal as well as to determine if there may be a change or a build-up of one sebum fraction in comparison to another, we repeatedly soiled and washed hair tresses. Single-surfactant systems only were tested. This was done in an effort to isolate the effects of the actual active ingredient and to prevent coformulated ingredients from masking the desired observations. Data was collected for 1, 10, and 20 soiling and washing cycles for the 2% soiling samples and 1 and 10 cycles for the 10% soiled samples. This could represent a period of one or two months of regular shampooing for an individual, depending upon washing intervals. Figures 5-8 represent the data obtained in this portion of the study. It is striking to note that there appears to be data supporting the notion that "shampoo fatigue" takes place in as few as 10 cycles. Of particular interest is the accumulation of the paraffinic compounds on the hair substrate. In almost every case the paraffinic and squalene residues were higher after 20 washing cycles than those observed after a single cycle. There did not appear to be an accumulation of the triglyceride, cholesterol, or fatty acid fractions after 20 cycles.