The key to ensuring complete penetration of permanent wave solution on coarse hair is

• A. Saturation of the cortex
• B. Equal length processing
• C. Temperature control
• D. Rapid application

Answer: (A)

Complete penetration of the perm solution relies on thorough saturation of the hair so the chemical can reach the cortex. The cortex is where the bonds are broken and reformed to create the curl, and the cuticle on coarse hair can act as a barrier. When the hair is fully saturated, the waving solution has consistent contact along the entire strand, allowing even diffusion into the cortex and uniform processing. If saturation is incomplete, some areas may stay underprocessed, leading to uneven curl—this risk is heightened with coarse hair because of its thicker cuticle and larger cortex. While factors like how evenly the product is distributed, temperature, and processing time influence how fast and how well the chemical moves, they don’t by themselves guarantee complete cortex penetration.