What is the function of a filler in hair coloring?

A filler plays a crucial role in hair coloring by equalizing porosity and preparing the hair for color absorption. When hair has varying levels of porosity, certain areas may absorb color differently, leading to uneven results. Fillers contain a combination of pigments and conditioning agents that help to create a uniform base, allowing color to adhere more evenly across the entire strand.

When applied, a filler helps to fill in gaps in the hair’s cuticle layer, making it possible for the color to penetrate more consistently. This is especially important in cases where hair has previously been lightened or is naturally porous. By equalizing porosity, fillers enhance the overall effectiveness of the color application process, ensuring that the desired shade achieves a better outcome and longevity.