Abstract: A composition of certain dyes with a category-2 hair bleach can simultaneously lighten hair up to seven levels and deposit various shades of color in a single step. The dyes are bleach-stable derivatives of azo, triarylmethane, thiazine, or nitro dyes. When linked at the ortho- and/or para-positions relative to the chromophoric centers and auxochrome groups located on or attached to the aromatic rings of these dyes, deactivating or weakly activating chemical groups enhance the dye stability in the alkaline bleach. The absence of ortho and/or para positioned deactivating or weakly-activating substituents, or the presence of strongly activating groups in these positions render the dye molecule susceptible to attack by the bleach and the eventual destruction of these dyes. These deactivating and protective chemical groups may be nitro, halogen, cyano, carboxyl, sulfonic, alkyl or aromatic groups, but not amino, hydroxy, alkoxy or alkylamide groups.

Abstract: A composition of certain dyes with a category-2 hair bleach can simultaneously lighten hair up to seven levels and deposit various shades of color in a single step. The dyes are bleach-stable derivatives of azo, triarylmethane, thiazine, or nitro dyes. When linked at the ortho- and/or para-positions relative to the chromophoric centers and auxoclirome groups located on or attached to the aromatic rings of these dyes, deactivating or weakly activating chemical groups enhance the dye stability in the alkaline bleach. The absence of ortho and/or para positioned deactivating or weakly-activating substituents, or the presence of strongly activating groups in these positions render the dye molecule susceptible to attack by the bleach and the eventual destruction of these dyes. These deactivating and protective chemical groups may be nitro, halogen, cyano, carboxyl, sulfonic, alkyl or aromatic groups, but not amino, hydroxy, alkoxy or alkylamide groups.

Abstract: The condition of hair or other keratin fibers can be evaluated by measuring the force required to obtain a first value of elongation of the fiber in the yield region of the force-elongation curve, and the force required to obtain a second value of elongation of the fiber in the yield region. The ratio of these two measured forces is then determined as a damage index for the fiber. It is found that a constant force ratio is obtained for wet virgin keratin fiber independent of fiber diameter or the source of the fiber. It is also found that the force ratio changes as a function of subjective or objective measures of chemical damage to the hair fiber. The force ratio or damage index can, therefore, be used for identifying hair care products suitable for application to the hair without inducing unacceptable damage. The tests may be performed with simple tensile testing apparatus without tedious examination of the hair under a microscope.