This could be a solution for individuals with curly and kinky hair to discover the most effective products for their hair.
Individuals with curly or kinky hair often face a bewildering array of choices when it comes to hair care. Recommendations on the most suitable hair products for a particular hair type are frequently contradictory, resulting in inconsistent outcomes.
However, scientists are now aiming to bring clarity to this confusion by identifying specific hair properties, such as the number of curls or coils in a given hair length, which could eventually assist users in selecting the perfect hair care product and achieving consistent outcomes.
The study was presented at the American Chemical Society’s (ACS) spring meeting, ACS Spring 2023.
“As an African American, I was born with very curly, seemingly unmanageable hair, and other ethnicities can possess similar hair properties,” remarks Michelle Gaines, Ph.D., the project’s principal investigator.
Gaines used to depend on chemical relaxers to straighten her hair, but stopped after becoming pregnant. She was then confronted with a plethora of options for styling and caring for her natural hair, which proved to be overwhelming. Limited guidance on the best options for her specific hair type, along with conflicting advice from various sources such as friends, YouTube videos, and other resources, only added to the confusion.
According to Gaines, there is clearly a significant knowledge gap that needs to be addressed, and she has taken it upon herself to fill that gap.
“As a polymer chemist and materials scientist,” she adds, “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.”
According to Gaines, who teaches at Spelman College, a historically Black women’s college, most prior research on hair properties has been conducted on straight or wavy strands from White or Asian individuals. She notes that less is known about what has traditionally been referred to as “African” hair, although researchers at Groote Schuur Hospital and the University of Cape Town in South Africa have published some findings on the topic.
Various systems have been developed to classify different types of hair, such as those created by L’Oréal and celebrity hairstylist Andre Walker. Walker’s system includes categories ranging from straight to kinky, with the latter encompassing tight coils and zig-zag strands with angular bends. While some people argue that all of these classification methods promote a preference for a smoother and straighter appearance, which has historical links to the preferential treatment of enslaved individuals with straighter hair and lighter skin, their primary goal is to assist users in selecting the most appropriate haircare products. Gaines found these systems to be effective for straight and wavy hair but lacking in the subtlety necessary to differentiate among the numerous variations of curly and kinky hair.
Gaines was curious to determine whether she could detect variations in properties beyond curl shape and tightness, and subsequently use those distinctions to create a more exact and quantitative classification scheme. She found eager undergraduate students at Spelman to assist her in this endeavor. Gaines and one of her students, Imani Page, are collaborating with Alfred Crosby, Ph.D., and Gregory Grason, Ph.D., from the University of Massachusetts Amherst, whose areas of expertise include material property characterization and modeling of complex materials and soft matter.
Using a texture analyzer and dynamic mechanical analyzer, the team measured the mechanical properties of wavy, curly, and kinky hairs. These instruments calculate force, stress, and other parameters as a strand is first straightened and then stretched until it breaks.
One of the team’s recent discoveries involved the “stretch ratio,” a newly created parameter that measures and compares the amount of force required to straighten a strand from its curled state. The ratio was determined to be insignificant for straight hair (as it cannot be uncurled), around 0.8 for wavy hair, 1.1 for kinky hair, and 1.4 for curly hair. This measurement could serve as an indicator of the initial curliness of a sample, providing a quantitative method for distinguishing between these hair types.
The team also examined geometric properties, such as the diameter, cross-section, and 3D shape of hair strands, using techniques like optical microscopy, scanning electron microscopy (SEM), and a camera. Furthermore, the researchers developed fresh parameters, such as the number of full waves, curls, or coils, known as “contours,” that they measured on 3-cm hair lengths. They discovered that wavy hair has less than one full contour in that length, curly hair has about two, and kinky/coily hair has roughly three or more. These findings suggest that people could classify their own hair by counting contours, according to Gaines.
Gaines has begun exploring the protective layer covering the surface of each hair fiber, known as the cuticle, in her most recent work. The cuticle is made up of flat cells that overlap like roof shingles. When exposed to water, shampoo, and conditioner, cuticles have a natural tendency to reversibly open and close. However, excessive acid and moisture retention can permanently damage the cuticles, causing them to remain irreversibly lifted and exposing the hair fiber’s inner cortex. Irreversibly lifted cuticles and cuticles that open and close easily make the strand more porous, causing greater moisture absorption.
Gaines’ initial findings indicate that the cuticle layers are larger and spaced further apart in wavy hair than in curly and coily hair. Additionally, the edges of the cuticle are smoother in wavy hair. These discoveries could help researchers explain why curly and coily hair dries out more quickly than wavy and straight hair. Ultimately, Gaines hopes that her team’s findings will enable developers to design and consumers to select the most suitable products for each of the diverse hair categories.
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