At temperatures exceeding 180°C, the alpha-helical structure of keratin proteins within the hair fibre begins to denature. This irreversible process compromises the integrity of the cortex, leading to visible changes at a cellular level.
Under a scanning electron microscope, undamaged hair exhibits a smooth, overlapping cuticle layer, much like roof tiles. These cuticular scales lie flat, reflecting light and offering a robust protective barrier to the inner cortex.
When exposed to excessive heat, however, the picture changes dramatically. The hydrogen bonds that stabilise the keratin chains break down, causing the cuticle cells to lift, crack, and sometimes even fragment.
This lifting reveals the underlying cortical cells. What was once a uniform, coherent surface becomes rough and porous, increasing the hair’s susceptibility to moisture loss and further mechanical damage.
The lipid layer, primarily composed of fatty acids such as 18-methyl eicosanoic acid (18-MEA), also suffers. This protective, hydrophobic coating is crucial for maintaining the hair’s lubricity and preventing dehydration. Heat degrades these vital glycerides.
Most conventional heat protection formulas rely on surface-level silicones to mitigate friction. Evera, conversely, formulates with specific botanical polysaccharides that create a flexible, breathable film, supporting the hair’s natural moisture balance even under thermal stress.
Internally, the heat causes voids and cracks within the cortex. The loss of cortical mass weakens the entire strand, making it brittle and prone to breakage. This internal degradation is often not immediately apparent to the naked eye.
Beyond the cuticle and cortex, the medulla — if present — can also be affected, though its role in structural integrity is less pronounced. The overall effect is a fibre that has lost its elasticity and tensile strength.
The hair’s ability to retain moisture is severely diminished due to the compromised cuticle. This leads to persistent dryness, frizz, and a dull appearance, as the damaged surface can no longer reflect light uniformly.
Understanding these microscopic changes underscores the imperative of mindful heat application and appropriate protective measures.
