386 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table V Preparation of Dye Dispersions Material Percentage References Dyestuff 0.3 Benzyl alcohol 4.0 Isopropanol 2.0 Miranol SM 3.5 Hydroxy ethyl cellulose 1.2 Water 89.0 28 20 16 2 white hair, by brushing, and left on the hair for 30 min at room tempera- ture. The hair is then rinsed in running water and dried. The following series of nine tests is proposed for determining whether a dye is satisfactory for use in semipermanent hair colors. Substantivity Substantivity, as used in this paper, is described as the amount of color retained by the hair after brush dyeing at room temperature and rinsing thoroughly. The dyed hair is examined for depth of shade and used for subsequent fastness tests. Fastness to Fading in Light This is determined in the usual manner in a standard fadeometer. It has been found that fastness to light of a dye applied at boiling tempera- ture often differs from that of the same dye applied at lower temperature. Examples illustrating this point are given in Table VI. Table VI Dip Dyeing of Hair in 0.1% Aqueous Solution at pH 3.0 Dyeing Temp Dyeing Temp Dye (øC) Fading (hr) (øC) Fading (hr) C.I. Acid Red No. 4 25 24 95-100 6 C.I. Acid Blue No. 168 25 6 95-100 26 In both cases the color produced at the boil was substantially darker than that obtained at room temperature. It is apparent that fastness to light values determined after application of dyes at the boil, as published by dyestuff manufacturers, cannot be accepted as valid for the same dye applied at room temperature. If we accept a light fastness rating of 10 hour-q to be satisfactory for hair dyes applied by brushing at room tern-

COLORING WITH SEMIPERMANENT DYES 387 perature, a large percentage of dyes developed for the textile industry would fail to pass this test. Shelf Life The dye solution, ready for application to the hair, is aged in a sealed bottle for 1000 hours at 50øC. One manufacturer (20) has suggested that the samples should be aged for double this time, or 3 months at 50øC. A sample of natural white hair is dyed with the aged solution and the color compared with that obtained previously with the same solution be- fore ageing. Fastness to Removal on Shampooing Fastness to shampooing is determined by soaking the dry-dyed hair in a concentrated shampoo solution for 5 min at room temperature, and rinsing throughly with warm water. The amount of color lost is esti- mated visually by comparison with the untreated sample. Scalp Staining A stripe of dye solution is placed on the inside of the forearm and al- lowed to remain there for 30 min. The arm is rinsed thoroughly with running water and dried with a towel. The amount of staining is ob- served and recorded. Most acid and basic dyes stain the skin substan• tially. Behavior When Mixed with Other Dyes Acceptable shades of hair colors are formulated with mixtures of dyes and their behavior is tested on hair swatches and heads. Effect of Prior and After Treatments The effect of bleaching and permanent waving both before and after dye application is determined on swatches and heads. The effect of con- ditioners, cream rinses, and hair setting solutions applied after dyeing is also important. Evaluation of Colors on Models Using Half-head Tests By the use of half-head tests direct comparisons are made of the results obtained with any new formulation with that produced by a commercial product that has wide acceptance in the trade. These tests are used to determine uniformity of color from tip to root section of the hair, sham- poo fastness, color build-up, and scalp staining.