ROLE OF DETERGENTS IN SHAMPOOS 119 This is further evidence that to- day's successful shampoos are not simply water solutions of detergents but are well-formulated mixtures, containing an acceptable balance of detergent, lather booster, foam modifier and hair conditioner. Syn- thetic detergents have also devel- oped a reputation for being too harsh on the skin. Recent investi- gations with commonly used deter- gents in home laundry preparations failed to show any sensitization and nothing was found to suggest that detergents were more damaging to the skin than comparable soap prod- ucts which must be quite alkaline (8). The synthetic detergents have by no means, however, completely replaced soap in shampoos. With proper formulation one may com- bine soaps with synthetics which have the power to disperse lime soaps. Such combinations are usu- ally characterized by a rich wet lather and leave the hair lustrous and manageable. There are several excellent refer- ences available on shampoo formu- lation (9, 10) and a number of articles have appeared on the lab- oratory evaluation of detergents for shampoos (2, 4, 5, 6). A few selected synthetic deter- gents suitable for use in shampoos were investigated for consumer ac- ceptance. Aqueous solutions of the detergents were prepared, contain- ing 12 per cent of the active anion. These were tinted and perfumed identically and adjusted to a pH value of 7.0 with hydrochloric acid.

120 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS These preparations were coded and panel tested among a group of women office workers. The panel members were asked to shampoo their hair in their normal manner once weekly but to refrain from using any hair dress- ing, wave set or rinses. Each shampoo was used over a two-week period and the panel members were then checked for their opinion as to latherability, manageability, luster, cleanliness and ease of wet comb- ing. The panel members all lived in a hard water area (approximately 150-300 p.p.m. hardness) and used unsoftened water in this test. The results obtained are presented in Table 2. For comparison, a solution of triethanolamine coconut soap at a pH of 8.5, prepared from a stripped coconut fatty acid and containing approximately 12 per cent active anion, was also included in this test. From the data in Table 2 it is interesting to note that soap alone was the least acceptable from the standpoint of hair luster, manageability and cleanliness although quite acceptable as to latherability. One'would expect that there should be a direct correlation between hair cleanliness and luster but this apparently is not the case. For example, sodium "coco" methyl taurate was rated best for "cleanliness" yet is only intermediate in luster. Perhaps cleanliness is a combination of factors related to degree of "degreasing" as well as the amount of insoluble calcium TABLE 3--A COMVARXSON or LABORATORY CLEANSING DATA FOR SELECTED DETERGENTS WITH PANEL TEST RESULTS Detergent Grease Panel Test Removal, % (% Voting Laboratory Good Cleansing Tests* Action) Triethanolamine "lauryl" sulfate 92 Protein fatty acid condensate 77 Triethanolamine dodecyl benzene sulfonate 73.7 Sodium octyl phenoxy polyoxyethylene sulfonate 81.7 Ammonium lauroyl isethionate 92.8 Sodium "coco" methyl taurate 95.0 Coconut soap 90.3 91 74 73 80 91 100 66 * Laboratory test data obtained from Barnett-Powers work (2, 4, 6), using 0.25% active detergent in tap water at 38øC. and magnesium salts deposited on the hair. In Table 3, there is presented a comparison of laboratory cleansing action and panel members' opinions on a few of the detergents tested. Surprisingly good correlation was ob- tained between laboratory cleansing tests and use tests for most of the detergents tested except soap. In the case of soap the heavy, dulling, lime soap deposit on the hair, undoubtedly, influences opinion as to cleanliness. It should be noted that the Barnett-Powers tests cited here were conducted in New York City tap water which is very soft indeed and much softer than the 150-300 p.p.m. tap water used in these panel tests. The solubility characteristics of the detergents studied in 350 p.p.m.