COLOR REACTIONS OF OXIDATION DYE INTERMEDIATES By Gvs S. KASS* and Lores HOEHN, JR.t Presented September 15-16, 1960, Semina% Chicago THE RAPIDLY expanding hair coloring market has focused the atten- tion of cosmetic chemists on all types of hair coloring methods and products with particular emphasis on oxidation dyes. A major marketing advance is now under way as oxidation hair coloring preparations break away from their traditional exclusive use in beauty shops to retail sale to the consumer for self application. A modern oxidation dye is a hair coloring preparation that is mixed with a developer, usually hydrogen peroxide, just prior to application to the hair. These products do not contain any dyes in the true sense of the word, except for certain nitro compounds, but contain chemical compounds or intermediates which form a dye upon oxidation In no other cosmetic product do so many variables affect the end result as it does in hair color- ings and this is especially true of the oxidation dyes. Among the many properties which must be taken into consideration when formulating such products are: 1. Color produced on the hair: for both natural and high fashion shades, depth or intensity and hue must be carefully worked out without undesirable highlights. 2. Color of the dye bath: It should bear a color relationship to the color it imparts to the hair. If the hair coloring is ash blonde, it is not desirable for the dye bath to be purple. 3. Viscosity of the dye bath: The current trend is to a viscous or semi- gelled dye bath so that it will not drip or run when applied to the hair. 4. Color fastness on the hair: The shades must be fast to light, sham- pooing, sunlight and perspiration. Certain hues such as the reds and blues are particularly sensitive. 5. Shelf life of the product: These products are sensitive to oxida- tion, trace metals, etc. Certain intermediates, which may be pres- ent in very small amounts, may lose their activity upon aging thereby changing the color produced on hair. 6. Effect ofpH: The degree of alkalinity has a pronounced bearing on * Alberto Culver Company, Chicago, Ill. t Nyanza Color and Chemical Co. Inc., Chicago, Ill. 146

COLOR REACTIONS OF OXIDATION DYE INTERMEDIATES 147 the rate of color development, intensity of color on the hair and bleaching action on the natural pigment. 7. Bleaching action on the natural pigment. Ammoniacal hydrogen peroxide will oxidize intermediates to dyes but at the same time may bleach the natural hair pigment. This may or may not be de- sirable. 8. Peroxide stability of the dye bath: Catalytic decomposition of the developer when mixed with the product can adversely affect the rate and completeness of color development. 9. Rate of color development: Ideally, color development should start leveling off in fifteen or twenty minutes so that there will be little difference in hue and intensity between a thirty and a forty-five- minute color development. This so that the first strands of hair colored will not be deeper in shade than the last strands to which dye was applied. 10. Staining of the scalp: Since the skin surface is also keratinous in nature it can also be dyed. Measures must be taken, however, so that such stains will readily shampoo out. 11. Condition of the hair after application: Oxidative dyeing of hair re- sults in undesirable physical and chemical changes. Careful formulation can keep these to a minimum. 12. Levelness ofdyeing: Certain shades (reds, silver, smoke, steel) have a tendency not to level on the hair but steps can be taken to mini- mize this. This is only a partial list and yet each one of these could easily be the subject of a technical paper. There are other variables which merit the concern of the cosmetic chemist but over which he excercises no control. These are with the consumer. Affecting the end color result are such factors as the condition of the user's hair, has it previously been dyed, tinted, bleached or permanent waved and what other preparations have been applied to the hair. It is no wonder that the instructions for the application of oxidation dyes are so complicated. Many of these problems were discussed in detail in a series of articles by Kass (1, 2, 3). In addition to these the cosmetic chemist must cope with some peculiar color problems when he starts to develop the many hair shades. Oxidation hair dyes are complicated products that may contain as many as 12 to 20 ingredients. They can be classified into several groups: dye vehicle or solvent, dye intermediates and modifiers, stabilizers and anti- oxidants, alkalizing and swelling agents. The composition of these groups, the interrelation of individual components, and the complexities of for- mulation and performance have been reviewed (1, 2, 3). It is the purpose of this paper to explore the interaction of dye intermediates in relation to color effects on the hair. Our findings and observations are primarily in the area of hair dye technology and we will delve only briefly into the theoretical aspects of the problems. The scope of this presentation is limited to dye intermediates commercially available for use in oxidation dyes.