Hair, a complex and intricate structure, reveals a different world when observed under a microscope. This magnified view shows the precise architecture of a single hair, offering insights into its health and how it responds to external treatments like dyeing. It also uncovers the changes that occur when hair undergoes a color transformation.
Inside a Strand of Natural Hair
A natural hair strand is composed of three distinct layers. The outermost layer is the cuticle, a protective shield made of overlapping, scale-like cells. These scales lie flat in healthy hair, contributing to its smoothness and shine.
Beneath the cuticle lies the cortex, which forms the main bulk of the hair shaft. This layer contains keratin proteins, providing strength and elasticity, and melanin granules, the natural pigments that determine hair color. The innermost layer, present in some hair types, is the medulla, a central core.
The Chemistry Behind Hair Color Transformation
Hair dyeing involves chemical processes that alter the hair’s natural structure to deposit new color. Permanent hair dyes use an alkaline chemical like ammonia or ethanolamine to swell and lift the cuticle scales, allowing dye molecules to enter the cortex. Once inside, hydrogen peroxide acts as an oxidizer, breaking down natural melanin pigments and simultaneously developing new dye molecules. These new, larger dye molecules become trapped within the cortex, providing a lasting color change.
Semi-permanent dyes operate differently, as they do not contain ammonia or peroxide. These dyes consist of smaller color molecules that can penetrate slightly into the cuticle and bond with the hair’s natural pigment. They stain the hair shaft, and the color gradually fades over several weeks or washes because the molecules are not permanently locked within the cortex.
Dyed Hair Under the Microscope: Appearance and Damage
When viewed under a microscope, dyed hair presents a different appearance compared to its natural state, particularly concerning the cuticle and cortex. The chemical processes involved in dyeing can cause the cuticle scales to appear lifted, uneven, or chipped, contrasting with the smooth, tightly packed scales of healthy, undyed hair. This lifting of the cuticle can increase hair’s porosity, making it more susceptible to moisture loss and further damage.
The cortex of dyed hair may show altered pigment distribution, where new, artificial pigments are visible alongside or replacing natural melanin. In cases of bleaching prior to dyeing, the cortex might appear more translucent due to the removal of natural melanin, or it could exhibit signs of internal structural changes. Microscopic examination can also reveal signs of damage, such as small cracks or breaks along the hair shaft, especially in repeatedly dyed or bleached hair. These imperfections highlight the physical stress hair undergoes during coloring, leading to increased fragility and a rougher texture.