Which condition causes hair fiber to soften and swell during processing?

• A. High Alkalinity
• B. Low Alkalinity
• C. Neutralizer
• D. Rinsing

Answer: (A)

High alkalinity raises the pH, which makes the hair cuticle lift and the cortex become more permeable. This softens the fiber and causes it to swell, allowing processing chemicals to penetrate and work on the disulfide bonds. The other options don’t cause swelling in the same way: low alkalinity keeps the cuticle tighter and reduces swelling; a neutralizer is used after processing to rebuild bonds and return the pH to normal; rinsing mostly removes products and doesn’t drive the chemical changes that soften the hair.