Morphological properties of hair and their variation when subjected to oxidation via chemical bleaching

Abstract

Four key morphological properties of hair were investigated in order to understand their variation in response to oxidation of the strand via bleaching. These were hair diameter, cuticle damage, porosity and fluorescence. Hair strands were oxidised by immersion in liquid and cream hydrogen peroxide of differing concentrations (3%, 6%, 9% and 12% w/v) and times, with changes to the structure recorded using three microscopic instruments: compound, scanning electron and fluorescence microscopy.Results indicated a proportional correlation between bleaching time and cuticle damage, which was further linked to porosity. In relation to fluorescence, strands with a higher proportion of pheomelanin were more fluorescent compared to darker hairs containing eumelanin. An unanticipated result of this investigation was the discovery of a dark point, named as it represented the time at which fluorescence decreased to a point where the strand was barely perceptible from the dark background of the image. After this point, fluorescence was found to build back up to its original or increased level, termed pseudo-fluorescence.