Have you ever noticed that your hair reacts differently depending on the area of your head? The nape curls, the temples wave, and the top of the head remains almost smooth. This observation is enough to understand why talking about “three types of hair” only tells part of the story.
Common classifications distinguish straight, wavy, and curly (or coily) hair. They provide a first reference point, but they overlook parameters that are just as important, if not more so, for choosing the right care.
Why multiple textures coexist on the same head
Most hair content presents each hair type as a separate category. In practice, the majority of people have multiple textures simultaneously on their scalp. Hair classified as “wavy” on top can display tight curls below the ears and almost straight strands at the temples.
This variation is explained by the shape of the hair follicle, which differs from one area to another. An oval follicle produces a wave, a very flat follicle generates a tight curl, and a round follicle gives straight hair. The distribution of these shapes is not uniform across the scalp.
The direct consequence: applying a single product everywhere means treating only one area correctly and neglecting the others. Observing your hair by zone (nape, temples, top, crown) before choosing a treatment yields much more consistent results than a global diagnosis. To delve deeper into these distinctions, you can read the Beauté Chic article on hair that details the basic categories.
Straight, wavy, and curly hair: what the basic classification really describes
The most widespread grid is based on the visible shape of the hair fiber. It remains useful as a starting point, provided you know what it measures and what it ignores.
Straight hair
The fiber grows straight from a round follicle. Sebum easily glides from the scalp to the tips, making this type of hair naturally shiny but also greasier at the roots more quickly. Light treatments, without heavy agents, are more suitable.
Wavy hair
The fiber forms a more or less pronounced S shape. The wave can range from a barely perceptible movement to a clear wave. Humidity greatly affects the behavior of this hair: it swells or relaxes depending on the humidity level.
Curly and coily hair
The flattened follicle produces a tight spiral. The tighter the curl, the more fragile the fiber is at the twist points. Curly hair often loses half of its visible length due to shrinkage, this retraction phenomenon that masks the actual length once the hair is dry.
These three categories describe the shape. They say nothing about how the hair absorbs water, resists stretching, or reacts to heat. To build an effective care routine, one must go further.
Porosity, elasticity, density: the invisible parameters that change everything
Two people with identical curls can have opposite care needs. The difference often lies in characteristics that are not visible to the naked eye.
Hair porosity
Porosity measures the fiber’s ability to absorb and retain water. It depends on the condition of the scales (cuticles) that cover the hair shaft.
- A low porosity means that the cuticles are very closed: the hair takes a long time to get wet and a long time to dry. Treatments penetrate poorly without heat or ambient humidity.
- A medium porosity indicates slightly open cuticles: the hair absorbs moisture in a balanced way and retains it properly. This is the easiest profile to maintain.
- A high porosity corresponds to very open cuticles, often due to repeated chemical or thermal treatments. The hair absorbs quickly but loses moisture just as quickly, resulting in a feeling of constantly dry hair.
To test your porosity, a simple gesture is enough: place a clean hair in a glass of water. If it floats for a long time, the porosity is low. If it sinks quickly, it is high.
Fiber elasticity
Elasticity reflects the internal strength of the hair. Healthy hair stretches about one-third of its length before returning to its original shape. A hair that breaks easily at the slightest stretch lacks protein in its cortex. A hair that stretches without returning lacks hydration.
This simple test guides the choice between a protein treatment and a moisturizing treatment, a decision that the straight/wavy/curly classification does not allow.
Density and thickness
Density refers to the number of hairs per square centimeter of scalp. Thickness concerns the diameter of a single strand. You can have a high density of fine hair or a low density of thick hair. Density and thickness determine volume much more than the shape of the curl.
Adapting your hair routine by crossing criteria
Knowing your curl type without knowing your porosity is like choosing a shoe size without measuring the width of your foot. Both pieces of information are necessary.
Do you have tight curls with high porosity? Thick plant butters and sealing creams will help retain moisture. Do you have waves with low porosity? A light spray applied to damp, warm hair will penetrate better than a rich mask that will stay on the surface.
- Start by identifying the dominant shape of your hair zone by zone (nape, temples, top).
- Test porosity using the glass of water method on a clean hair, without product.
- Evaluate elasticity by gently stretching a wet hair between two fingers.
- Adapt product textures (light, medium, rich) to each area rather than to the entire head of hair.
The hair care market reflects this evolution. “Clean label” ranges and products formulated for natural textures are progressing much faster than conventional products in the European Union, a sign that more and more consumers are abandoning systematic straightening in favor of routines that respect the actual texture of each area.
The classification into three types remains a shared vocabulary, practical for orientation. It does not replace careful observation of one’s own hair, zone by zone, criterion by criterion. It is this cross-reading, shape plus porosity plus elasticity, that transforms a generic routine into a truly tailored routine.
