Patent ID: 7060111

Claim:
A method of providing more vibrant, natural and long-lasting color to hair comprising carrying out the following sequential steps: a) contacting the hair with a dye precursor mixture producing a color change, ΔE, of at least about 0.15 units when measured by the In-Vitro Piedmont Color Retention Test, said dye precursor mixture comprising: i) a primary intermediate having a pKa in the range from about 3 to about 10 selected from the group consisting of the neutral or salt forms of para-phenylenediamine, derivatized para-phenylenediamines, para-aminophenol, substituted para aminophenols, 4,5-diaminopyrazole, substituted 4,5-diaminopyrazole, polyamino-pyrimidine, hydroxy-polyaminopyrimidine, and other substituted polyaminopyrimidine and mixtures thereof, i) an optional coupler having a pKa in the range from about 3 to about 10 wherein the pH of the precursor solution is selected such that less than 50% of the molecules comprising the primary intermediate and the coupler are in their anionic form when they first contact the hair, and b) contacting the hair with a developer mixture capable of inducing oxidation of primary intermediate and coupler in the precursor mixture that is in contact with the hair to form colored species, wherein the dye precursor mixture remains in contact with the hair for a time period of from about 0.5 to 60 minutes before the hair is contacted with the developer and wherein the primary intermediate and coupler remain substantially inactive during this time period.