Quantifying hair shape and hair damage induced during reshaping of hair.

The manipulation of hair shape, either to straighten or curl hair, is carried out on a grand scale in the hair care consumer market. Often, such changes are brought about through chemical or physical treatment, resulting in changes to hair chemistry. In this article, we review existing and present new data on methods to assess the efficacy of such treatments, mostly concentrating on imaging technologies used in conjunction with image analysis. In addition, we introduce spectroscopic imaging techniques and fluorescence spectrophotometry as tools to assess the biochemical state of the hair fiber as a result of hair shape modification regimens. Finally, we demonstrate how the structural integrity of the fiber is monitored with dynamic scanning calorimetry and traditional mechanical testing of the tensile properties of hair.