LANOLIN DERIVATIVES IN SHAMPOOS 785 mixing time too short, the rate of the foam volume buildup is at a maximum and equilibrium is not attained. If the speed is too fast or the mixing time too long, differences can be masked. For example, the influence of sebum on foam properties is practically negligible after five minutes beating time, since the foam-depressing effects of the fatty material are overcome by the extra work used in generating the foam. A further consideration in selecting this combination of speed and time was the good correlation reported by New between foams produced on heads in salon tests and foams produced in the laboratory under these test conditions. Drainage volume was recorded after five minutes so that indications of potential instability could be noted. If the drainage time is too short or too long, differences between the foams are less apparent. The five- minute reading was selected after several different foams had been char- acterized by recording drainage at intervals of 30 seconds for extended time periods. The five-minute interval provided maximum differentia- tion between the various foams in a reasonable period of time. Plotting drainage rs. time or determining the time required for the total collapse of each foam proved to be time-consuming and contributed nothing sig- nificant toward characterizing the foams. Results are reported as per cent drainage rather than direct volume readings to allow a more meaningful comparison between foams of different densities. It is, of course, possible for the volumes drained from two foams of different specific gravities to be identical after five minutes. But the foam with the higher specific gravity would yield a larger volume of liquid on total collapse. It is, therefore, actually drain- ing more slowly than the foam with the lower specific gravity. Treating the results as per cent drainage takes into account the potential volume on total collapse and the differences in the weights of the foams that are being drained. All the foams were examined visually for luster and bubble size, and were handled to evaluate feel. After more than 100 tests had been run, it was possible to establish acceptance criteria for both sFeeifie foam volume and per cent drainage. The specific foam volume must be at least 13.5 ml/g and the per cent drainage after five minutes must be be- tween 60 and 70%. Acceptable shampoo foams must meet both criteria. Foams that have specific volumes lower than 13.5 ml/g and that drain less than 60% in five minutes consist of small dry bubbles. These foams lack the luster and rich wet feel desirable in shampoo foams. As

786 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS long as the per cent drainage remains significantly below 60, a higher specific foam volume provides little improvement in the aesthetic qualities of the foam. Foams that drain more than 70% in five minutes, regardless of the specific foam volume, are generally characterized by large wet bubbles. These foams are difficult to manipulate, tend to collapse rapidly, and feel relatively watery. RESULTS AND DISCUSSION The additives were tested at concentrations of 1, 2 and 5% in the shampoo formulation at each of four test conditions: deionized water at 23øC moderately hard water (150 ppm Ca ++) at 23øC deionized water at 45 øC and in the presence of synthetic sebum in deionized water at 45 øC. These test conditions were judged to be representative of some probable "use-environments" in which shampoos might be used. The data are summarized in Tables II and III. Table II Effect of Additives on Specific Foam Volume (ml/g) Under Four Test Conditions Test Condition Deionized Water Additive and 150 ppm Sebum, Concentration (%) 23 ø C 45 ø C Ca + +, 23 ø C 45 ø C Control 14.1 14.8 13.6 13.2 Derivative No. 16 1 14.4 14.7 14.4 13.3 2 14,8 14.3 15.0 14.0 5 14.4 13.1 13.6 13.5 Derivative No. 25 1 14.2 14.0 14.0 14.0 2 14.3 12.8 14.6 13.8 5 14.2 13.4 14.8 12.7 Derivative No. C-24 1_ 14.8 13,5 13.6 13.5 2 13.8 13.4 15.7 13.0 5 14.2 13.2 13.8 12.7 Derivative No, 75 1 13.9 13.8 13.9 13.5 2 13.7 14.0 12.8 14.3 5 14.0 13.6 16.3 13.9 Derivative No. 97 1 14.1 13.9 14.4 13.7 2 14.0 13.9 15.0 13.3 5 13.1 13.2 14.7 14.4 Derivative No. 98 1 13.8 14.8 14,7 12.9 2 12.5 14.5 14.6 13.3 5 13.7 14.4 14.0 12.5 POE (10) S.A. i 14.3 13.3 15.4 13.3 2 14.2 13.3 14.2 12.5 5 13.4 13.3 13.4 13,4