11.3 Classifications of Haircolour: Temporary Through Permanent

Classifications of Haircolour

Exam Focus: The comparison table is the reference for the whole chapter. The distinction that matters most in practice and on the exam is deposit-only versus lift-and-deposit: temporary, semi-permanent and demi-permanent all deposit, and only permanent colour and lightener remove natural pigment.

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1. Haircolor Classifications Overview

┌─────────────────────────────────────────────────────────────────────────────┐
│                     HAIRCOLOR PENETRATION & CHEMISTRY                       │
├─────────────────────────────────────────────────────────────────────────────┤
│  1. Temporary: Large direct molecules coat cuticle surface only. No lift.   │
│  2. Semi-Permanent: Small direct molecules partially enter cortex. No lift. │
│  3. Demi-Permanent: Precursors + low developer deposit into cortex. No lift.│
│  4. Permanent: Aniline precursors + ammonia + developer polymerize in cortex│
│     to lift natural melanin and deposit synthetic color simultaneously.     │
└─────────────────────────────────────────────────────────────────────────────┘

Comprehensive Haircolor Comparison

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2. Temporary Haircolor

Temporary haircolor is a non-oxidative haircolor formulated with large, direct dye molecules that are too large to penetrate the cuticle layer of the hair shaft.

Physical Action & Characteristics

• Mechanism: The large pigment molecules physically coat and adhere to the outer cuticle scales.
• Chemical Formulation: No developer ($H_2O_2$) or alkaline swelling agent is used. The product has an acidic pH.
• Longevity: Removed completely in one single shampoo.
• Clinical Indications:
  • Neutralizing unwanted yellow tones in natural gray or white hair (e.g., violet temporary rinses).
  • Refreshing faded color between salon services.
  • Special event styling, color sprays, chalks, and color mousses.
  • Safe on compromised or highly fragile hair because no chemical bond disruption occurs.

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3. Semi-Permanent Haircolor

Semi-Permanent haircolor is a non-oxidative, direct-dye haircolor formulated with smaller pigment molecules that partially penetrate past the cuticle scales and lodge into the outer layers of the cortex.

Physical Action & Characteristics

• Mechanism: Formulated as pre-formed direct dyes; does not require mixing with hydrogen peroxide developer.
• Self-Penetrating: The smaller molecular size allows self-penetration without significant chemical swelling of the cuticle.
• Longevity: Lasts through 4 to 6 shampoos, fading gradually with each wash without creating a noticeable line of demarcation (regrowth line).
• Formulation Rules:
  • Cannot lift or lighten natural hair color.
  • Only deposits tone or deepens existing levels.
  • Blends minor gray hair (up to 15-20%) but will not provide 100% opaque gray coverage.
  • Mildly alkaline or neutral pH.

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4. Demi-Permanent Haircolor (Deposit-Only Color)

Demi-Permanent haircolor is an oxidative haircolor designed to deposit color without lifting natural melanin. It is often referred to as deposit-only haircolor or gloss/glaze.

Chemical Action & Formulation

• Mechanism: Uses small unoxidized dye precursors combined with a low-volume developer (typically 5-volume to 10-volume, or 1.5% to 3% $H_2O_2$).
• Cuticle Action: Formulated with a mild alkalizing agent (such as monoethanolamine [MEA] or aminomethyl propanol [AMP] instead of high ammonia) that gently opens the cuticle without stripping the hair's natural melanin granules.
• Cortex Action: Dye precursors enter the cortex and oxidize into larger color molecules that remain trapped inside the hair shaft.
• Longevity: Lasts 4 to 6 weeks (approximately 20 to 28 shampoos), slowly washing out with minimal visible regrowth line.

Clinical Uses in the Salon

1. Gray Blending: Blends up to 50% gray hair seamlessly without harsh root lines.
2. Toning Pre-Lightened Hair: Ideal as a post-lightening toner or gloss to refine blonde shades.
3. Color Refreshing: Applied to faded mid-lengths and ends while permanent color is applied to the new growth (color balancing/glazing).
4. Corrective Fillers: Replaces missing undertones in damaged or porous hair prior to darker color application.
5. Adding Gloss & Shine: Clear demi-permanent glosses condition and seal the cuticle without depositing pigment.

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5. Permanent Haircolor & Aniline Derivative Chemistry

Permanent haircolor is an oxidative haircolor that penetrates the cortex to simultaneously lift natural melanin and deposit synthetic color in a single chemical service. Once processed, permanent color cannot be shampooed out.

Chemical Components of Permanent Haircolor

┌─────────────────────────────────────────────────────────────────────────────┐
│                     PERMANENT COLOR CHEMICAL REACTION                       │
├─────────────────────────────────────────────────────────────────────────────┤
│  1. Alkalizing Agent (Ammonia/MEA) ──> Swells cuticle; opens pathway       │
│  2. Aniline Derivatives (Precursors)──> Small uncolored dye molecules enter │
│  3. Developer (Hydrogen Peroxide)  ──> Oxidizes melanin (lift) & oxidizes   │
│     dye precursors into giant polymerized color molecules (deposit)         │
│  4. Permanent Lock                 ──> Large molecules trapped in cortex    │
└─────────────────────────────────────────────────────────────────────────────┘

1. Alkalizing Agent (Ammonia - $NH_3$ / Ammonium Hydroxide or MEA):
   • Raises the pH of the hair (typically pH 9.0 to 10.5).
   • Softens and swells the protective cuticle scales, allowing dye molecules to enter the cortex.
   • Triggers the rapid decomposition of hydrogen peroxide into water and active oxygen free radicals.
2. Oxidative Dye Precursors (Aniline Derivatives / Para-phenylenediamine - PPD):
   • Small, uncolored synthetic coal-tar derivative compounds.
   • Because they are extremely small, unoxidized molecules, they pass easily through the swollen cuticle into the cortex.
3. Polymerization Reaction:
   • Inside the cortex, the uncolored dye precursors encounter the active oxygen released from the hydrogen peroxide developer.
   • The precursors oxidize and polymerize (link together into massive, multi-branched color molecules).
   • Because the polymerized molecules are far too large to pass back out through the cuticle scales, they become permanently trapped inside the cortex.
4. 100% Gray Coverage: Permanent haircolor is the only category that provides 100% opaque gray coverage on resistant, unpigmented hair.