Studies on hair damage and demelanization by ultraviolet light

Abstract

The effects of ultraviolet and sunlight radiation on the decolorization and damage of human black hair were studied.
Effects of ultraviolet light were studied by exposing hair samples to a carbon-arc lamp, while the solar effects were examined by exposing hair samples to natural daylight.
Hair damage was evaluated from the ratio of the force at 20% elongation of untreated hair fibers and treated ones. The change of the color was evaluated by measuring the hue value of hair strands. It was also evaluated from the reflectance of hair fibers when scanned at 500nm by a chromatoscanner.
Exposing black hair fibers immersed in deionized water to ultraviolet or sunlight lowered their tensile properties and fading was also observed. The same phenomena were confirmed in case of sea water too. In dry condition, exposing black hair fibers to ultraviolet or sunlight did not change their color and tensile properties. Furthermore, we found out that as the pH values of immersing solution increased, the ultraviolet light irradiated hairs became less tensile, and fading was also accelerated.