The Science Behind Hair Bleaching: What Really Happens to Your Hair?

When hair is bleached, it undergoes a complex chemical process that alters its structure and pigment. Here’s a detailed breakdown of what happens, step by step:

1. The Chemical Reaction

Bleach (usually a mix of **ammonia** and **hydrogen peroxide**) penetrates the hair shaft and triggers two key processes:

Oxidation: Hydrogen peroxide breaks down the hair’s natural **melanin** (pigment) by oxidizing it, stripping away color molecules.

Alkaline Lift: Ammonia swells the hair cuticle (the outer protective layer), allowing bleach to reach the cortex (inner layer where pigment resides).

2. Structural Damage

Cuticle Damage: The raised cuticle scales never fully close again, leading to:

Porosity: Hair absorbs and loses moisture unevenly.

Frizz & Breakage: Weakened cuticles snag and split.

Cortex Breakdown:

Keratin Loss: Bleach breaks down disulfide bonds in keratin proteins, weakening hair’s tensile strength.

Protein Degradation: Hair becomes brittle and prone to snapping.

3. Color Transformation

Melanin Removal:

Eumelanin (black/brown pigment) oxidizes first, turning hair **orange → yellow**.

Pheomelanin (red/yellow pigment) is harder to remove, often leaving brassy tones.

Final Result: Hair lightens to pale yellow (Level 9–10), which can then be toned to achieve cool blondes or pastels.

4. Factors Influencing Damage

Developer Strength Higher volumes (30–40 vol) lift faster but cause more damage.

Processing Time Overlapping or leaving bleach on too long melts the hair.

Natural Hair Color Darker hair (Level 1–4) requires more aggressive bleaching.

Previous Chemical Treatments Relaxed, permed, or dyed hair is more fragile.

5. Common Side Effects

Dryness: Loss of natural oils and moisture.

Elasticity Loss: Hair stretches less before breaking.

Brassiness: Underlying warm tones resurface as melanin fades.

Split Ends & Breakage: Severe protein loss leads to “gummy” texture.

6. Aftercare to Minimize Damage

Protein Treatments: Rebuild keratin with masks

Moisturizing: Use sulfate-free shampoos and hyaluronic acid conditioners.

Heat Protection: Avoid styling tools or use thermal protectants.

Toning: Neutralize brass with purple/blue shampoos

Trim Regularly: Remove split ends every 6–8 weeks.

- Consult a professional for dark-to-light transformations.

For best results, always prioritize hair health over speed!