Why brows turn gray?

Many artists conflate the properties of carbon molecules with those of the carbon black colorant (CI 77266) when discussing its persistence in the skin. Often, they correctly attribute the stability of small carbon black colorant particles (around 100 nm) and carbon particles with a high proportion of hydrocarbons, such as those found in Furnace Black (Black 2), to the overall behavior of carbon molecules. However, for the sake of precision, it should be noted that such particles are composed of thousands, if not tens of thousands, of molecules. The retention of a grayish tone in the skin is particularly due...