CLEANING HAIR 341 21øC Least removed Most removed EST P.W. C 16 C 14 CHOL C 18 C 18:21 43øC Least removed Most removed EST P.W. CHOL C 14 C 18:21 C 16 C 18 As previously observed (1), the ester and paraffin wax fractions are the most difficult to remove. The order of the other components varies with temperature. At the 95 % level, removal of the C14, C16, C18, and C18:21 acids and cholesterol is different from the waxes and esters (at 43øC), with marginal overlap at the lower temperature where the C16 and C14 components are also more difficult to remove than the other fractions. At 2 IøC, however, there are two statistical groupings, and this increases to three at 43øC, indi- cating slightly greater selectivity as temperature increases. SLES-2-WASHED HAIR Figure 3 illustrates the SLES-2 sebum removal data for 2 iøC and 43øC. Analogous to the ALS observations, the sebum component removal at 2 IøC is significantly different • SLES-2/21C • SLES-2/43C 100 80 ß 60 o E • 40 20 0 C 14 C 16 C 18:21 C 18 CHOL P.W. EST $ebum Component Figure 3. Removal of sebum components by SLES-2: Ten soil/wash cycles, 2 IøC and 43øC.

342 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS from, and lower than, that at 43øC (p = 0.05). An alternative representation of these data is: 21øC Least removed ?dost removed P.W. EST CHOL C 18:21 C 16 C 14 C 18 43øC Least removed ?dost removed EST P.W. C 18:21 C 14 CHOL C 18 C 16 Again the most difficult components to remove, at either temperature, are the esters and paraffin waxes--the nonpolar fractions. The other five fractions show some se- quence change as the temperature increases. As observed for the ALS data, there is an increase in the number of statistical groupings from three to four as wash temperature increases, again suggesting an increase in selectivity. Data for both ALS and SLES-2 indicate a slightly greater selectivity at the higher tem- perature (43øC). This can be explained by considering extreme wash temperatures. Theoretically, as temperature decreases, it is possible to reach a point at which no sebum component is removed and no selectivity of removal occurs. Similarly, at very high wash temperatures (above those practicable for washing hair on heads), all sebum components may be removed at close to 100%--again no selectivity. Between these extremes, one may hypothesize that selectivity, and removal, increase as the wash tem- perature increases and that a limiting value, dependent on the surfactant, is reached at the highest feasible wash water temperature for shampooing. Since the removal of a component is related to its melting point as well as surfactant-sebum-substrate inter- actions, it is logical that temperature should have an effect on sebum component re- moval selectivity. COMPARISON OF DATA: ALS AND SLES-2 One-way ANOVA analysis for the total sebum removed from hair at both temperatures shows (95% confidence level): Least removed ?dost removed ALS/21 ALS/43 SLES- 2/21 SLES-2/43 Figures 4 and 5 illustrate the comparisons. These graphical representations clearly show that SLES-2 is the more effective detergent for all sebum components (all differences significant at p = 0.05). SQUALENE In the earlier work on selective sebum component removal (1), the issue of the squalene component was discussed in view of its absence from all chromatograms of control or washed sebum extracts, although it was clearly present in calibration chromatograms of the sebum used to soil the hair. It was not evident why squalene had disappeared from