Barbering Science
What this domain tests
This domain covers hair and skin structure and the chemistry behind cutting, coloring, relaxing, and disinfection. Questions ask you to predict what a chemical or tool will do to the fiber.
Core rules and concepts
- Structure: cuticle, cortex, medulla. The cortex holds melanin and the disulfide bonds that set shape.
- Bonds: disulfide bonds are permanent; salt bonds shift with pH; hydrogen bonds reset with water and heat.
- pH: relaxers near pH 12–13 break disulfide bonds; acids and conditioners tighten the cuticle.
- Growth cycle: anagen (years), catagen (weeks), telogen (about three months); daily shedding is normal.
- Diagnostics: porosity and elasticity tests guide chemical decisions before service.
Worked example
A client bleached three weeks ago requests a relaxer. Reasoning: bleach oxidizes and weakens the cortex, and a strong alkaline relaxer on compromised fiber risks breakage. Perform a strand and elasticity test; if elasticity is poor, decline the relaxer and offer alternatives. Reassess after new growth provides intact fiber.
Traps that cost marks
- Relaxing over recently bleached hair.
- Overlapping relaxer onto previously relaxed scalp.
- Skipping patch and strand tests.
- Assuming a temporary bond change behaves like a permanent one.