If you want to show that your hair product or styling device prevents hair damage or hair breakage, or restores hair properties after being damaged, it is useful to perform a single-fiber tensile experiment.

In these studies, hair fibers are extended until they break.  The forces required to stretch and break the hair are good indicators of internal hair properties and overall hair strength.  Nearly all damaging treatments (bleaching, UV-light, heat styling etc) affect hair's mechanical properties, so tensile experiments are usually the first test recommended for hair damage or repair claims measurements.  These experiments can be used to investigate both hair damage prevention and restoration of hair properties after specific treatments.

Hair fiber mechanical properties are very sensitive to both the water content of the hair and the humidity of the air; hair is much easier to break when it is wet.  Tensile experiments can be performed in both wet and dry conditions.  It is widely believed that wet hair experiments focus on the properties of the intermediate filament proteins (keratins) in the cortex, whereas dry hair experiments investigate the combined properties of the intermediate filament proteins and the keratin associated proteins in the matrix. The experts at TRI can provide about which test protocol is most appropriate for your experiment.