118 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS "flash" foam. In many instances the synthetics will give a copious lather which is characterized by a loose, lacy bubble size and a "dry" feel. Such lathers do not have the rich, elegant feel of the dense, wet soap lather and, unless modified by additives, will have poor consumer acceptance. Another class of commonly used detergents gives rise to a sensation of friction between the hands during the rinsing step. This sensation is totally different from the slippery feel one gets when using soap and must be modified if the finished product is to obtain good consumer ac- ceptance. Still another class rinsing and drying, This may be due to acceptable sensation Certain synthetic of detergents gives a wonderfully rich lather but, on gives a sensation of tackiness on the skin and hair. substantivity of the product but is not a pleasant or to the consumer. detergents may do too thorough a job of cleansing, leaving the hair dry and unmanageable. This condition may be alleviated by cutting down the concentration of detergent and by the addition of fatty ingredients (3) to the shampoo. It is of interest to note that shampoos based on synthetics have been unfairly accused of being too strong in cleansing action and, thus, presum- ably removing all the oil from the hair and scalp. While this may be true of the synthetic detergents when used alone (4), it certainly is not true of the successful synthetic detergent shampoos, which constitute the major portion of today's markets (5). For example, Barnett and Powers (6) showed that most synthetic deter- gents were from 89 to 98 per cent efficient in removing grease from wool. In this test wool yarn, spun in the grease, was gently shaken in 0.25 per cent active solutions of the detergent at 38øC. But the same test run on successful commercial shampoos (7), which are based on some of these very same detergents, showed tremendously lower cleansing power in the order of 4 to _53 per cent (see Table 1). TABLE 1--EVALUATION OF CLEANSING POWER OF SHAMPOOS* Shampoo Per cent Soil Removalt Marrows 15.2 Breck 23.6 Hudnut 36.1 Prell 35.5 Halo 42.6 Drene 4.4 Toni 35.8 Rayve 32.2 Lustre Cream 22.5 Marlene 53.4 Helene Curtis 48.8 * Results reported by Consumers Research, October, 1951. t Using Barnett-Powers Test (4).

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.