HAIR COLORING--MODERN FORMULATION CONSIDERATIONS 293 but removable at will with a simple shampoo instead of tedious and damag- ing stripping or bleaching operations. Such a product should not rub off wet or dry and should not bleed when subjected to rain, swimming or per- spiration. It should be safe and simple to use. It should not be affected by other hair products. It should not react differently to damaged hair than to relatively normal hair. In other words, it should improve on the traditional concept of the hair dye by being relatively foolproof and there- fore proof against nuisance lawsuits. It must have these qualities to balance the fact that it suffers from its main attraction: not only may it be removed at will with a simple shampoo, but it will a/ways come off with a simple shampoo and therefore must be re- applied constantly. Nevertheless, such products seem inevitable in prod- uct planning for the near future and the formulator must therefore be pre- pared to produce them as near to the perfect ideal as possible. SURFACTANTS AND "CONDITIONERS" The formulator who wishes to improve on the standard capsule rinse con- taining 1 per cent dye plus 99 per cent citric acid normally starts with the idea of adding some sort of hair conditioner. His product at pH 2 seems to work very well in giving the small amounts of color desired. If he uses strictly nonionic conditioners such as the lanolin derivatives and other "superfarting" agents, he will not get into too much trouble except for the problem of emulsifying at such a low pH. Occasionally, these materials may interfere with the action of his dyes by adsorbing onto the hair before the dye solution can make really good contact. An example is mineral oil, often added to formulation to give "combability" by making the hair more slippery during the application. Another was patented by Beste (1) who found that certain alkylphenoxyethanol nonionic surfactants could be used in the dual function of emollient and dye rate controller, since they prefer- entially sorb onto the hair and present a barrier to the dyes. Due to its amphoteric nature, keratin will also tend to sorb both anionic and cationic materials to varying degrees depending on their polarity. This results in a "conditioning action" if the materials happen to be some- what fatty or oily. They leave the hz. ir lustrous, which means "healthy" by current advertising definition. Today's color creme rinse formulations often contain dyes complexed with fatty materials to give such a look to the hair. These adsorbed layers generally conduct electricity well also and thus impart antistatic properties to the hair so that it stays rather liraply in place when combed. The total effect of these products is often described incorrectly as softening the hair, a much maligned verb now equated to con- ditioning, even though damaged hair is weak and soft while normal hair is firm and hard. Putting a fatty sheath on the hair may make it look lus- trous and feel silky, but anyone who sells substantive hair dyes can attest 1o

294 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS the fact that it has not repaired any damage. Such dyes are perfect color- imetric indicators of the extent of damage suffered by the hair. When complexing anionic dyes with cationic agents to give these effects, it is sometimes necessary to use ethoxylated cationic materials for two reasons: they are less irritating, and they give a complex which is rather weak and more hydrophilic. In the same way, cationic dyes can be reacted with ethoxylated anionics and there are systems where it may be preferable (2, 3, 4, 9) to titrate anionics and cationic surfactants together in thepresence of dissolved dye. In the latter case, the dye then often partitions between the water of solution and the resulting water insoluble complex. It is wise to remember that such dye-surfactant complexes will not color the hair well except from a dispersion of relatively large particle size. Any agent which disperses them too well can destroy their effectiveness. On the other hand, if they agglomerate in very large micelies, they will produce gross surface films which rub off quite easily. Getting the proper dispersion is generally the most tricky part of formulating with such complexes. Many additives to the product--whether for reducing foam or enhancing it, for wetting or penetration purposes or for conditioning--may affect the final color yield quite drastically. T• Us• ov Gt•s ^st) S•Qt•s•rv•^•rxs Gums are used in hair dyes for the usual cosmetic reasons. They thicken the solution, make it feel richer, reduce dripping of the dye during applica- tion, may give wave setting properties and can reduce crocking. Methyl cellulose and other gums have been advocated (26, 29) as media for solid solutions of dyes in stick form. Gums may also be used to form dye com- plexes with special properties. Most natural gums are anionic and there- fore precipitate basic dyes. A cationic starch was recently introduced which shows some promise for formulations containing acid dyes. Sequestrants have many uses in a hair dye. Most dyes are sensitive to hard water and develop precipitates or color changes in the presence of some metallic ions. It is taken for granted that the manufacturer of hair color- ants realizes this and that he uses deionized water in his product. Even then however, he may occasionally contaminate it by such oversights as the use of copper or brass fittings in his plant. Also, his customer may dilute his product with very hard water. Precipitates formed under such condi- tions are not always visible in the bottle, but they tend to give streaky, dull effects (10) on the hair and the color will rub off more easily than usual. It is also wise to remember that keratin reacts with any polyvalent metal ion. Magnesium salts are used to "load" or build up the weight of wool in this manner, similarly to the weighting of silk with tin salts. Calcium, copper, iron, magnesium and the heavy metals will thus build up on hair which is constantly in hard or sea water. The body also excretes ingested