Final answer:
High highly porous hair, which quickly absorbs color, has lifted or open cuticles that allow easy penetration of moisture and chemicals. However, this also means the hair may become dry or damaged as it does not retain moisture well. This is in contrast to low porosity hair, which resists such absorption due to tightly bound cuticles.
Step-by-step explanation:
When the cuticle of the hair is lifted and the hair is overly porous, absorbing color quickly, the hair porosity is defined as high porosity. This means that the hair cuticle, which is the outermost layer of the hair shaft, opens up and allows moisture and chemicals to penetrate the hair more easily. This can, for instance, lead to rapid but often uneven absorption of color during a dyeing process. However, because the hair cuticle is lifted or open, it does not retain moisture as well, making the hair liable to become dry or damaged.
Conversely, low porosity would be characterized by a tightly bound cuticle layer with overlapping scales that lay flat, thus resisting moisture and chemical treatments. Medium or normal porosity hair strikes a balance between these extremes, allowing just the right amount of moisture to enter while preventing too much from escaping.
Learn more about Hair Porosity