New ways to measure curls and kinks could revolutionise natural hair care, say scientists. Black women and others with tightly curled hair face a confusing array of products that can work in vastly different ways from head to head.
Counting the curls could become the key to picking the perfect product that will actually do what it says on the tin. Study lead author Dr Michelle Gaines, of Spelman College in the US, used to rely on chemical relaxers to straighten her tresses.
Once she got pregnant she stopped, only to enter the overwhelming world of store-brought products. Limited guidance, and conflicting advice from friends YouTube videos, all made choosing the right product harder. She said the major knowledge gap around 'African' hair must be closed.
Until now, research was conducted on wavy or straight strands from white or Asian people. Less is known about “African” hair, as it has traditionally been known. L’Oréal developed systems to classify different types ranging from straight to kinky, a term for tight coiled and zig zag strands with angular bends.
Dr Gaines felt these functioned well for straight and wavy hair but lacked the nuance to distinguish the massive variety in curly and kinky hair. She said: “As an African American, I was born with very curly, seemingly unmanageable hair, and other ethnicities can possess similar hair properties.
“As a polymer chemist and materials scientist, I thought it would be great to start a project where I could study the nuances of my hair, because I felt like it wasn’t very well understood.”
Dr Gaines and her Spelman University team investigated properties beyond curl shape and tightness, using the differences to develop a more precise and quantitative system. They measured the mechanical and textural properties of wavy, curly and kinky hair. Force, stress, and other parameters were measured as the strand is uncurled and then stretched until it breaks.
Together they invented a “stretch ratio” that would quantify and compare the force needed to uncurl a strand until straight. Measurements could indicate the initial curliness of a sample, distinguishing type from type.
The ratio was negligible for straight hair, 0.8 for wavy, 1.1 for kinky and 1.4 for curly. Number of curls per 3cm length of hair was counted too - wavy hair has less than one full contour per length, curly has around two, and kinky or coiled hair has three or more.
These counting techniques could be done by anyone at home. Diameter, cross section and the 3D shape of strands were measured using optical microscopes, scanning electron microscopy (SEM), and a camera.
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In the research presented at an American Chemical Society meeting, Dr Gaines also discovered why curly and coiled locks dry out faster than wavy and straight. To do so she tested the protective layer of each hair fibre, known as the cuticle, consisting of flat cells that overlap like roof shingles.
Cuticles tend to open and close reversibly when exposed to water, shampoo and conditioner. However, they can be permanently damaged by excessive acid and moisture retention. Such damage can cuticles to be irreversibly lifted, exposing the inner cortex of the hair fibre, making the strand more porous, and causing more moisture absorption.
The scientist discovered cuticle layers are larger and further apart in wavy hair than curly and coiled hair. Cuticle edges are also smoother than those in wavy hair.
