What does hair porosity describe?

Porosity describes the hair's ability to absorb moisture, liquids, and chemicals, which is related to the condition of the cuticle. High-porosity hair (often from damage or chemical processing) has a raised or open cuticle and absorbs quickly but may process unevenly; low-porosity hair has a tight cuticle and resists absorption. Porosity strongly affects chemical services like color and perms, so it must be assessed beforehand. Understanding porosity — and how it influences product behavior — is a key part of hair analysis tested on the exam.