Investigations of vegetable tannins as hair dyes and their interactions with pre‐bleached hair fibres

Objective 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....