ROLE OF DETERGENTS IN SHAMPOOS 117 and truly cleansing and scouring the skin and hair gives an unacceptable effect. During the past twenty years the emphasis in shampoo advertising has shifted from a preparation that thoroughly cleans the hair to a preparation that leaves the hair fragrant, soft, manageable and lustrous and, inciden- tally, cleans the hair and scalp mildly (1, 2). That the cosmetic industry is approaching an acceptable shampoo is evidenced by the fact that the sale of shampoos has grown to its present size in the past twenty years. This success is not entirely due to chance or sophisticated advertising. Time and again it has been proven--that when a product fulfills a need'--it will usually succeed, even if it costs more than its less acceptable predeces- sor. It is for this reason that aerosol shave creams have made such in- roads into the sale of creams in tubes and jars that home permanents replaced the curling iron that aerosol hair sprays have largely replaced the bottled gum hair sets and that shampoos have replaced the bar of soap. When soft water is available, the bar of soap is ideal for a man's head of hair, but is inconvenient for a woman to use. The need was felt for a preparation that would wet the hair more readily and would lather and give a richer lather faster. Thus, the bar of soap gave way to liquid potash soap preparations. The liquid soap shampoos had a limited success but it was obvious that further product improvement was needed. Soap sham- poos are fine in soft water and, when formulated with the proper ratio of C•2 to C•8 fatty acids, they give a rich, wet, dense, copious lather, which rinses easily and leaves the hair lustrous and manageable. In hard water areas the latherability of the soap shampoo decreases and, what is much more serious, calcium and magnesium soaps are precipitated onto the hair, leaving a film of insoluble lime soaps. In extremely hard water areas the lime soap precipitated on the hair makes combability dif- ficult, leaves the hair tacky and may actually lead to dirtier looking hair. Women would not tolerate these results and corrected this condition by following the soap shampoo with a lemon or vinegar rinse. These acid rinses helped to remove the hard water soaps, leaving the hair more nearly lustrous. It is not surprising, then, that, with the advent of synthetic detergents, the major growth and development of the shampoo market occurred. Synthetics were a group of water-soluble materials that lathered well in hard water and did not leave a heavy insoluble precipitate on the hair. As experimentation proceeded with the synthetic detergents, it became obvious that shampoos with good consumer acceptance required something more than a colored, perfumed solution of a detergent. In many instances the synthetic detergents do not lather well in the presence of sebum--the natural oil of the hair and scalp--hair dressings, sweat, and wave set residues. They also require the addition of lather boosters to enhance the

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).