Hair comes in a wide variety of curl patterns ranging from straight to curly. Hair science holds a great impact on society in the cosmetics industry and in biomedicine. Over the last few decades, there has been rising  societal interest for curly headed people to embrace their natural curls, which promoted an increased  desire for  employing healthier methods for hair care. This new interest in embracing natural hair led to the invention of new classification systems to better categorize hair according to its natural curling morphology, beyond the traditional and highly limited system – Caucasian, Mongolian, and African. Andre Walker’s classification  system (1-4(a-c)) is the existing gold standard for classifying hair type. However, the system uses qualitative measures to classify hair type, which makes the system vague and exclusive to the full diversity of phenotypic differences. While Walker’s system does provide guidance on typing hair according to its natural curl pattern, a more defined system is still necessary. The goal of this research is to use quantitative methods to create a comprehensive system of naming and categorizing hair types that is inclusive to the full range of phenotypic variations. This is accomplished by distinguishing the mechanical and physical properties of several types of human hair samples. Mechanical properties were tested using a texture analyzer and a dynamic mechanical analyzer, which provided clear data on the force, stress, strain, and stretch ratio required to both uncurl and stretch hair strands to fracture. Morphological properties including pitch, contour length, radius and diameter were measured using scanning electron microscopy (SEM), optical profilometry, and optical microscopy.  From the resulting data, correlations were made where hair with increasing curliness displayed increased ellipticity, decreased elasticity, and increased porosity. This data will be used to draw more conclusions on the contribution that morphology has on hair fiber mechanics.

Quantitative approach to reclassifying hair according to fiber mechanics

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