Methods adapted to evaluate products for textured hair: Combing force and breakage

Objective To demonstrate the ability of adapted or developed test methods to quantify friction and breakage in textured hair. Methods Walker type 4 hair was used for illustrations. The modified Garcia & Diaz's wet friction method was used to evaluate hair combability and product ability to reduce the combing forces. Hair breakage was evaluated using both a conventional dry tensile test and a repeated combing test method that had been developed for type 4 textured hair. Both the number of broken fibres and the percentage of prematurely broken fibres were used to assess treatment efficacy in reducing breakage. Results Wet friction method: The proposed method adaptations include recommendations for substrate preparation, combing 16 times while rewetting hair every 5 times and evaluating maximum force instead of area under the curve. The benchmarking study showed products' ability to reduce hair friction by 50%–60%, with antipollution treatments performing comparably to those suggested for textured hair. We have also demonstrated that the natural oils do not reduce hair friction despite reducing breakage due to combing. The repeated wet combing method filled the gap experienced by the industry using repeated grooming techniques. We proposed grooming treated coily hair tresses in a wet state (manually) using a comb for a total of 100 strokes, rewetting every 20 passes. The evaluation of broken fibres showed reduced breakage after the use of conditioning and lubricating treatments (by 38%–64%), with silicone oil providing the greatest reduction (72%) and confirming the method's sensitivity. Tensile testing demonstrated high textured hair prevalence for premature breakage, which linearly depends on the water content in the hair. The study examining different treatment layering methods suggested that it is possible to sufficiently coat wet textured hair to reduce water migration out of the hair, as indicated by Young's modulus evaluation. It also showed that correctly managing premature breakage via plasticizing hair can outweigh the break stress reduction observed in healthy hydrated fibres. Conclusions The examined methods are shown to be appropriate to evaluate both the manageability and breakage of naturally curly hair, as well as test products' ability to improve these properties.