A guide to hair product testing techniques

The health of human hair plays a crucial role in both male and female appearance, and has a strong psychological and social importance. Beautiful, strong and healthy hair is broadly desired. However, hair is highly exposed to harsh factors such as heat, chemical treatments, pollution and watering that can cause damage on the hair physicochemical properties. There is great interest not only in developing products for the protection and recovery of damaged hair, but also in developing effective protocols to investigate the efficacy of innovative hair care products. Claims for cosmetic products, as well as hair care products, are a strategy to obtain successful marketing and promotion. These claims need to be substantiated by efficacy tests, whether they be in vivo, ex vivo, or in vitro studies.

In a Personal Care Magazine article written by Ashland researchers, a range of hair testing techniques are presented that can show damage sustained, from the cortex to the hair surface, for both quantitative and/or qualitative techniques. They present how they use their Texture Analyser, amongst several other instruments, to measure hair combing/detangling (mean force to comb) and hair strength (maximum force to break).

Meanwhile, other scientists at Ashland have just published a paper entitled Development of a three-point cantilever bending technique to study the mechanical properties of hair styling ingredients. A detailed description is provided for a user-friendly, quick method to measure the mechanical properties of styling ingredients on hair. They provide guidelines for three-point cantilever bending tests of straight hair tresses treated with conventional and naturally-derived styling polymers. Indices have been developed to characterise the force-distance curves and are designated as E1, F1, position of F1, post-fracture gradient, toughness, E10/E1, and F10/F1. These indices provide an overall characterisation of the stiffness, flexibility, elasticity, and plasticity of polymer-treated hair.

The three-point bending fixture they present has recently been updated by Stable Micro Systems. See the wide range of other probes and attachments for hair and hair product testing that provide even more parameters for the characterisation of hair properties.