8. Conclusion

In the field of hair color, as in many other areas of formulation in general, the technical performance of the product is no longer enough. Consumers are now particularly attentive to the composition of the products they use. In addition to technical and economic constraints, formulators today must strive to develop formulations that are as environmentally-friendly and harmless as possible. Colorists, meanwhile, are seeking to broaden the range of shades available, bringing brilliance, highlights and depth to their stains. Color is now defined by a multitude of colorants. In the case of permanent colorants, it is derived from a combination of bases, which provide the color base, and couplers, which modify the shades to add highlights. Hair color must no longer be perceptible; it must look "natural". Scientists therefore set out to imitate nature, and biomimetic approaches were developed...