Adsorption Properties of Hair 338 accepted explanation for this occurrence involves adsorption taking place on a non-swollen substrate, while desorption occurs from a swollen state where an increased number of exposed adsorption sites are present. Somewhat surprisingly, it is rather difficult to alter the water- hair adsorption and desorption isotherms. Many will be familiar with uncomfortably high humidity conditions on hot summer days and the commensurate inability to retain hair styles, and, as such, it may be presumed that hair adsorbs still higher amounts of water under these conditions. This, however, is incorrect, and the shapes of adsorption isotherms are recognized to alter only slightly with temperature4-6 (a reason for style failure under these conditions will be hypothesized later). Figure 4 shows adsorption isotherms for wool and water at 25oC and 40oC (data from the work of Bull4) and illustrates how higher temperatures actually give rise to slightly lower adsorption. Figure 3. Hysteresis between the adsorption/desorption isotherms of hair and water