What is porosity in hair, and why does it matter for chemical services?

• A. Porosity describes how easily hair absorbs and releases moisture; it affects processing time and product choice.
• B. Porosity is the surface smoothness of cuticle.
• C. Porosity measures hair length.
• D. Porosity is the hair's thickness; it affects color deposit.

Answer: (A)

Porosity describes how easily hair absorbs and releases moisture. This matters for chemical services because the speed at which chemicals penetrate the hair shaft, and how much moisture the hair holds or loses during processing, depends on porosity. Hair with high porosity has more open cuticles, so products and moisture move in and out quickly. That means processing times can be shorter and you often use milder formulas or lower developers to avoid overprocessing and dryness, though it may require more conditioning since moisture can escape readily. Hair with low porosity has tightly closed cuticles, making penetration slower, so you may need longer processing times or heat and sometimes stronger solutions to achieve the desired result. Understanding porosity helps you tailor timing and product choice for even results and healthier outcomes during chemical services.