* Penetration: Bleach (typically hydrogen peroxide and an alkalizing agent like ammonia) works by penetrating the hair shaft. The cuticle (the outer layer of the hair) needs to be opened to allow the bleach to reach the melanin (the pigment that gives hair its color).
* Oxidation: Once inside, the bleach oxidizes the melanin molecules. This process breaks down the melanin, effectively lightening the hair. The more melanin that's broken down, the lighter the hair becomes.
* Protein Damage: Unfortunately, bleach isn't selective about what it oxidizes. Along with melanin, it also oxidizes and damages the proteins that make up the hair's structure (keratin). These proteins are essential for hair strength, elasticity, and overall integrity.
* Weakening and Breakage: When the protein structure is damaged, the hair becomes:
* Weaker: Less able to withstand tension and stress.
* More Porous: The cuticle becomes rough and raised, leading to increased moisture loss.
* Brittle: Lacking elasticity, making it prone to snapping.
* Dry: Unable to retain moisture due to cuticle damage.
* Overlapping and Excessive Processing: Repeated bleaching, especially when overlapping previously bleached hair, compounds the damage, leading to significant protein loss and severe breakage. Over-processing also significantly damages the hair, as the hair structure is compromised.
In simple terms, bleach lightens hair by breaking down its color pigment, but in the process, it also weakens and damages the proteins that give hair its strength and structure. This protein damage is what ultimately leads to hair breakage.