J. Soc. Cosmet. Chern., 25, 165-170 (March 3, 1972) The Kinetics of Dye Rinse from Bleached Hair MICHAEL Y. M. WONG, Ph.D.* Presented May 24-25, 1971, Seminar, Washington, D.C. Synopsis--Experimental data were obtained on the KINETICS of DYE RINSE from BLEACHED HAIR. It was found that dyes of different molecular sizes had significantly different behavior towards the effect of hair bleaching. INTRODUCTION There is still considerable uncertainty regarding the chemistry of hair bleaching however, it is generally agreed that oxidative bleaching has several side effects (1-3): changing the chemical constituents of the hair, opening the highly crosslinked structure inside the hair fiber, and possibly degrading the cuticle layer on the surface. These modifications conceivably alter the dyeing properties (4, 5) of hair, in particular the kinetics of dye rinse. Aside from the obvious practical implication, re- sults on the kinetics of dye rinse from bleached hair can be of consider- able theoretical interest, at least qualitatively. This study has been limited to rinse-out kinetics of direct dyes. How- ever, the ionic character and molecular sizes of the dyes have been con- sidered. * Clairol Research Laboratory, 2 Blachley Road, Stamford, Conn. 06902. 165

166 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS •TO SPECTROPHOTOMETER FROM PHOTOMETER Figure 1. Schematic of rinse-out apparatus EXPERIMENTAL Figure 1 is a schematic showing the continuous measurement of dye concentration as the dyed hair is being rinsed. The rinsing was done inside a rectangular box made of transparent plexiglass. One side of the box could be detached for inserting and changing samples. Inside the rinsing box the hair sample was confined in a rectangular cage. One part of the cage was made from a thin slide of plastic with a hole cut in the middle. A piece of 1/16 in. wire screen was mounted on the bottom of the hole. When the hair sample was in place, a second simi- larly constructed piece was put on top of it as a cover, and secured to it by a set of screws. The cage was then slid into the box between two slots. In each run of the experiment, four such cages were usually used for 1 g of hair sample. With the help of a liquid pump, water was circulated through a cell in a spectrophotometer* where the dye concentration was continuously recorded. The rinsing of dyed hair was done at room temperature. Bleached hair was obtained by treating normal brown hair with a commercial hair bleach? The bleached hair was rinsed with water for 2 hours to leach out any residual persulfate. The bleached sample was then dyed* to equilibrium. The concentration of the dye bath was 1 g/liter. The residual dyes on the surface of the hair were removed by leaving the dyed sample in a centrifugeõ at 10,000 rpm for 45 min. * Gilford 2000, Beckman Instruments, Inc., Fullerton, Calif. • Ultra Blue, Clairol Inc., Stamford, Conn. * Dyes were prepared at Clairol Research Lab. except Acid Green 25 and Deorlene Orange, which were obtained from Ciba Chemical and Dye Co., Fair Lawn, N.J. õ International Centrifuge, Model HG, International Equipment Co., Needham Heights, Mass.