| A | B |
|---|
| Density | the number of hairs per square inch |
| Texture | diameter of a hair strand |
| Porosity | ability to absorb liquid |
| Low porosity | cuticle is tight; hair is resistant and takes longer to process color. |
| Average porosity | Cuticle is slightly raised; hair is normal. |
| High porosity | Cuticle is lifted: hair is overporous and absorbs color quickly. |
| Eumelanin | melanin that gives black/brown color to hair |
| Pheomelanin | melanin found in red hair |
| Cuticle | outer layer of hair; gives hair 20% of its strength |
| Cortex | Middle layer of hair; gives it elasticity and 80% of its strength |
| Medulla | inner layer of hair |
| Contributing pigment | pigment under the natural hair color |
