6.2 Haircolor Classifications & Developers

Haircolor Classifications & Developers

Professional haircolor products are categorized into four distinct chemical classifications based on their formulation, molecular size, depth of hair shaft penetration, and longevity. Understanding these classifications—along with the chemical mechanics of hydrogen peroxide ($H_2O_2$) developers—allows cosmetologists to select the safest, most effective formula for every hair type, porosity condition, and desired outcome.

Chemical haircolor is broadly split into two primary categories: non-oxidative (which requires no developer) and oxidative (which requires mixing with an oxidizing agent like hydrogen peroxide).

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Non-Oxidative Haircolors

Non-Oxidative haircolors do not require a developer or chemical oxidation process to create color changes. They simply deposit direct dyes onto or slightly within the cuticle layer.

1. Temporary Haircolor

Temporary haircolor is a non-oxidative formula designed to alter the hair's shade temporarily without changing its physical or chemical structure.

• Molecular Structure: Contains very large pigment molecules that are too large to pass through the cuticle layer into the cortex.
• Mechanism: The pigment molecules adhere physical-chemically to the exterior surface of the cuticle scale layer.
• Longevity: Washes out completely with 1 shampoo.
• Formulations: Color rinses, hair chalks, color sprays, mascaras, colored mousses, and color-depositing shampoos.
• Chemical Impact: No lift, no porosity alteration, and zero chemical damage to hair keratin.

2. Semi-Permanent Haircolor

Semi-permanent haircolor is a non-oxidative direct-dye formulation that offers moderate durability without lifting natural pigment.

• Molecular Structure: Contains smaller pigment molecules than temporary colors, along with some large molecules.
• Mechanism: The smaller molecules slide past the cuticle scales and partially enter the outer edge of the cortex, while larger molecules remain on the cuticle surface.
• Developer Required: None. It is applied directly from the bottle to shampooed, towel-dried hair.
• Longevity: Fades gradually with each shampoo, lasting through 4 to 6 shampoos.
• Ammonia & Lift: Contains no ammonia and cannot lift natural pigment; it can only deposit shade tone equal to or darker than the starting level.

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Oxidative Haircolors

Oxidative haircolors require mixing an alkalizing agent and dye precursors with an oxidizing developer (hydrogen peroxide) to initiate a chemical oxidation reaction inside the cortex.

3. Demi-Permanent Haircolor

Demi-permanent haircolor (also known as deposit-only color) is an oxidative haircolor formulation designed to deposit color without lifting natural hair melanin.

• Chemical Composition: Formulated with an alkalizing agent other than ammonia (such as monoethanolamine, MEA) and oxidative dye precursors.
• Developer Strength: Mixed with a low-volume developer (typically 5 Volume to 10 Volume hydrogen peroxide).
• Mechanism: Low pH alkalinity gently expands the cuticle layer, allowing dye precursors to enter the cortex where hydrogen peroxide oxidizes them into medium-sized color molecules.
• Lifting Capability: Zero lift of natural pigment under normal conditions. It deposits color to deepen level, change tone, or refresh faded ends.
• Longevity: Typically lasts 4 to 6 weeks (fading gradually over 12 to 24 shampoos).
• Gray Blend: Excellent for blending unpigmented (gray) hair up to 50% without harsh root regrowth demarcation lines.

4. Permanent Haircolor

Permanent haircolor is the workhorse of salon color services, capable of lifting natural melanin and depositing artificial pigment simultaneously in a single application.

• Chemical Composition: Contains alkalizing agents (ammonia), aniline derivative dyes (small uncolored dye precursors such as paraphenylenediamine, PPD), and conditioning agents.
• Developer Required: Mixed with 10, 20, 30, or 40 Volume hydrogen peroxide developers.
• Mechanism: Ammonia swells the cuticle and enters the cortex. Inside the cortex, ammonia activates hydrogen peroxide, releasing oxygen. Released oxygen accomplishes two simultaneous reactions:
  1. Lifts Natural Pigment: Lightens existing eumelanin and pheomelanin granules.
  2. Oxidizes Aniline Derivatives: Small precursor molecules combine and polymerize into large, permanent artificial color molecules that become permanently trapped within the cortex structure.
• Gray Coverage: The absolute standard for 100% gray coverage.
• Longevity: Permanent; remains in the hair shaft until trimmed or chemically lightened, though tonal tone may fade over time.

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Comparison of Haircolor Classifications

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Developers & Hydrogen Peroxide ($H_2O_2$) Mechanics

An oxidizing agent (developer or catalyst) is an acidic pH solution of hydrogen peroxide ($H_2O_2$) mixed with oxidative haircolors and lighteners. When combined with alkaline permanent color or lightener, hydrogen peroxide decomposes, releasing free oxygen molecules ($O_2$) that oxidize dye precursors and lighten natural melanin.

Measuring Developer Concentration

Developer concentration is measured by Volume (U.S. standard measuring volume of oxygen gas released) and Percentage (international metric system measure of active hydrogen peroxide by mass):

• 10 Volume (3% $H_2O_2$):
  • Primary Function: Used for deposit-only applications or minimal lift (less than 1 level).
  • Best Used For: Darkening hair level, depositing tone at the same level, toning pre-lightened hair, and fine hair textures.
• 20 Volume (6% $H_2O_2$):
  • Primary Function: Standard developer strength for achieving 2 levels of lift and 100% gray coverage with permanent haircolor.
  • Best Used For: Single-process gray coverage, standard permanent color applications, and on-scalp cream lightener applications.
• 30 Volume (9% $H_2O_2$):
  • Primary Function: Used to achieve 3 levels of lift with permanent haircolor.
  • Best Used For: High-lift blonde colors, resistant coarse textures, and dramatic single-process lift.
• 40 Volume (12% $H_2O_2$):
  • Primary Function: Provides maximum lift of up to 4 levels of lift with permanent oxidative color.
  • Caution: 40 Volume is an off-scalp strength. Never use it in an on-scalp application or with an on-scalp lightener, because of the severe risk of chemical irritation and scalp burns.

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Chemical Safety & Mixing Standards for Board Exams

• Always mix haircolor in non-metallic bowls (plastic or glass) using plastic whisks or tint brushes. Metallic containers chemically react with hydrogen peroxide, causing rapid oxidation, heat production, and chemical degradation.
• Respect manufacturer mixing ratios strictly (e.g., 1:1 or 1:2 ratio of color cream to developer).
• Always measure developers precisely with a measuring cylinder or digital gram scale rather than visual estimation.