Scientific findings have revealed that hair dye has been around for nearly 2,000 years. Australian researchers discovered that Greeks and Romans had mixed lead oxide with slaked lime to color grey hair black.
Researchers prepared a batch of dye following the 2-millenia old formula and immersed 50 mg of human hair in the dye for three days to conduct a close study. The hair that was immersed gradually turned black. When the hair was observed under a microscope, the scientists found nanocrystals of lead sulfide in the hair shaft.
Reportedly, black color resulted from the reaction between lead and the sulfur from amino acids found in hair keratins. Five nanometer lead sulfide crystals formed by the reaction resembled lead sulfide quantum dots that are today made by modern scientific techniques.
The researchers are hopeful that the discovery will lead to future developments in mineral-based nanomaterials. They also believe the research may prove beneficial to developing hair dyes.