Yak belly hair has been proposed to replace human hair to study the effects of hair dyes . The particular advantage of Yak belly hair is the absence of the coloring molecule melanin, which is unfavorable for example for investigations using Raman scattering. To replace human hair, one has to ensure that the properties of Yak hair closely resemble to human hair. This was the starting point for our investigations: We used various techniques such as small-angle X-ray scatting (SAXS), scanning electron microscopy (SEM) and Raman spectroscopy to get information on the structural difference. It turned out that Yak hair is in general much more porous than human hair, which has to be taken into account in dyeing experiments. Furthermore, we performed tensile tests of both types of hair to determine their mechanical properties. The results for Yak and human hair are thoroughly compared, in particular with respect to the hierarchical structure, which is typical for many biological tissues.
 P.D.A. Pudney, E.Y.M. Bonnist, K.J. Mutch, R. Nicholls, H. Rieley, S. Stanfield. “Confocal Raman Spectroscopy of Whole Hairs”. Appl. Spectrosc. 2013. 67(12): 1408-1416