Hairdressing Science & Artistry

Hairdressing Science & Artistry

Trichology, Chemical Architecture, Precision Design & Salon Management

1. Trichology & Structural Hair Chemistry

Professional hairdressing is rooted in trichology—the biological study of hair, its structure, growth cycles, and chemical composition. Hair is primarily composed of keratin, an insoluble fibrous protein synthesized from 18 amino acids, predominantly cysteine. Understanding the internal physics of the hair shaft enables stylists to perform chemical restructuring, color transformations, and conditioning treatments without compromising structural integrity.

4.5 – 5.5

100,000

0.3 – 0.5 mm

Natural Hair/Scalp pH Range

Average Scalp Follicle Count

Average Daily Hair Growth Rate

1.1 Anatomy of the Hair Shaft

The human hair strand consists of three distinct concentric layers, each performing unique structural roles:

1. The Cuticle (Outer Shield)

2. The Cortex (Core Strength)

Consists of 6–10 overlapping translucent scale layers

Forms approximately 90% of the hair shaft's total weight.

made of hardened keratin. Protects the delicate interior

Contains fibrous protein chains, natural melanin pigment

cortex and regulates moisture absorption. Healthy

granules, and chemical bonds that determine elasticity,

cuticles lie flat, reflecting light for natural shine.

tensile strength, and natural texture.

3. The Medulla (Central Core)

4. Follicle & Dermal Papilla

The innermost core composed of soft keratin cells and

The living root assembly located within the dermis. The

air spaces. Commonly present in coarse hair types and

dermal papilla contains blood vessels supplying nutrients

often absent in fine or naturally blonde hair strands. Has

required for cell division and hair growth during the active

no direct role in chemical services.

growth phase.

1.2 Internal Chemical Bonds

The polypeptide chains in the cortex are cross-linked by three principal bond types: Hydrogen Bonds: Weak, physical side bonds easily broken by water or thermal heat, reformed upon drying or cooling. Responsible for temporary styling sets.

Salt Bonds: Weak, ionic side bonds broken by changes in pH (acidic or alkaline solutions). Neutralized when the hair returns to its natural pH equilibrium.

Disulfide Bonds: Strong, chemical covalent bonds joining sulfur atoms in adjacent cysteine amino acids. Broken only by chemical reducing agents (perming/relaxing) or strong oxidizers.

Hairdressing Science & Artistry: Professional Guide

Page 1 of 7