A pore’s ability to store liquid is called porosity. Average hair porosity is the benchmark for hair color manufacturers. They craft their hair colors to work best on average porosity hair.
Hair that is in good condition will exhibit average porosity. Average porosity hair will hold color for the life cycle of a hair color application. This typically lasts 4-6 weeks.
Hair that is lacking in pores will need to be treated with a softener before hair color can be applied. Otherwise the hair will not hold the color.
Hair that has too many pores will easily absorb a hair color but will not retain it. Shortly after the coloring process, the hair will shed the color. To properly color overly porous hair, first treat it with a demi-color or filler.