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The aim of this work was to optimize our natural hair dyeing system which we described in our previous work and to compare with other dyeing systems. Therefore, we investigated concentration limits of matcha and mordant and compared this new dyeing method with commercial permanent systems on the market. Completely unpigmented hair tresses were dyed with matcha powder (camelia sinensis) and iron(II)-lactate. To investigate the wash fastness and concentration limits, the differently dyed hair tresses were spectrophotometrically measured. The comparison of the damage potential for which cysteic acid is an indicator was measured by NIR. The concentration of matcha and mordant are responsible for the intensity of the color results. The higher the matcha or the mordant concentration, the darker the color results of the dyed hair tresses. Hair damage of matcha mordant dyeing is comparable with results of commercial permanent hair coloration systems. Moreover, the results of wash fastness of matcha mordant dyed hair tresses is comparable and even better by tendency to permanent colored hair tresses.

The aim of this work was to investigate an alternative hair-dyeing method with vegetable colourants as the tannins, as well as the impact of pre-treatment as the bleaching process. METHODS: Untreated, 1, 2 and 3 times bleached hair tresses that were dyed with tannins in combination with metal salts were characterized. The wash fastness and the colour strength of the vegetable-dyed hair tresses were spectrophotometrically investigated. RESULTS: To determine the colour strength KS and the wash fastness of vegetable-dyed and pre-bleached hair tresses, a three-dimensional colour coordinate system-CIELabwhich describes the visual spectra is used. The distance between two colours in the CIE-Lab colour space is expressed by DEvalues , which are used to identify the wash fastness of the vegetable dye. The hair tresses that had been 3 times pre-bleached showed the highest colour strength and the best wash fastness. The fixation of the tannin-mordant complexes on the hair fibre proceeded effectively just when the hair tresses were bleached before the dying process. It is suggested that the sulphonic acid groups, which increase after bleaching hair, interact with the tannin-mordant hair dye and lead to stronger cross-links between keratinous fibres and tannin-mordant complexes. It was observed that the colour strength of the vegetabledyed tresses correlates with the bleaching process. CONCLUSION: The presented results demonstrate that the fixation of the vegetable tannin-mordant dying solution on the hair fibres succeed effectively on pre-bleached hair tresses. a une plus forte cohesion entre les fibres k eratiniques et les complexes tanin-mordant. Une corr elation entre l´intensit e de couleur des m eches color ees par les pigments v eg etaux et le degr e de d ecoloration a puêtre observ ee. CONCLUSION: les r esultats pr esent es dans cette etude d emontrent que la fixation du pigment vegetal tanin-mordant en solution est possible et efficace sur des m eches de cheveux d ecolor ees au pr ealable.