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2. Hair Diagnostics & Consultation Science Before executing any technical service—cut, chemical treatment, or color—a structured trichological diagnosis must be performed. Evaluating hair physical properties prevents mechanical damage, over-processing, and adverse scalp reactions.

2.1 Physical Hair Characteristics Matrix

Physical Property

Porosity

Technical Definition

Clinical Testing Method

Chemical Service Impact

Ability of the cuticle layer to

Float Test / Strand Slide Test

Determines color absorption speed

absorb liquids and moisture.

(sliding fingers from tip to scalp).

and developer strength selection.

Stretch Test: Stretch dry hair

Indicates disulfide bond integrity;

(20%) or wet hair (up to 50%).

dictates perming or lightening safety.

Ability of hair to stretch and Elasticity

return to length without breaking.

Number of individual hair

Density

strands per square inch of scalp.

Texture

Scalp Visual Check (classified as Low, Medium, or High).

Individual strand diameter

Single Strand Feel or Micrometer

(Fine, Medium, Coarse).

Measurement.

Dictates product quantity requirements and subsection thickness in cutting.

Coarse hair requires higher

processing times; fine hair processes rapidly.

2.2 Hair Growth Cycles (Trichodynamics)

Scalp follicles progress through three distinct biological growth phases continuously:

Anagen (Active Growth Phase)

Catagen (Transition Phase)

Lasts between 2 to 7 years. Approximately 85%–90% of

A brief 2 to 3 week regression period where the follicle

all scalp follicles are in the anagen phase at any given

shrinks, detaches from the dermal papilla, and halts hair

time, actively synthesizing keratin protein.

fiber production.

Telogen (Resting Phase)

Exogen (Shedding Phase)

Lasts 3 to 4 months before natural shedding occurs.

The final sub-stage where the fully detached club hair

Normal daily shedding ranges from 50 to 100 strands as

exits the follicle lumen entirely, completing the cyclical

new anagen hair begins pushing up.

turnover process.

Safety Protocol: The Strand & Patch Test Prior to applying permanent oxidative hair color or chemical relaxers, stylists must perform a Patch Test (Predisposition Test) 24–48 hours in advance behind the ear or inside the elbow to check for p-Phenylenediamine (PPD) allergic sensitivity, alongside a preliminary strand test on isolated hair cut-offs.

Hairdressing Science & Artistry: Professional Guide

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