The hair is only slightly porous and feels soft and supple. The surface reflects the light giving the hair its shine. The older a piece of hair is, the more physical and chemical stress it has been through. The edges of the cells open along the length and at the tips of the hair, or they are worn away. The hair becomes porous and feels straw-like and rough. It loses its gloss because the uneven surface no longer reflects the light evenly.