To change the natural wave pattern of hair, the side bond of what layer of hair must be broken?

• A. Cortex
• B. Cuticle
• C. Medulla
• D. Epithelium

Answer: (A)

Hair texture and the natural wave pattern come from the cortex, where keratin fibers are held together by side bonds. To change the wave pattern with chemical processing, these bonds must be broken so the keratin can rearrange and then reform in a new configuration. The outer cuticle only protects the hair and doesn’t determine curl, the medulla is the hair’s central core and isn’t where these bonds control texture, and epithelium isn’t a part of hair structure in this context. So, the side bonds in the cortex are what must be broken.