Chapter 10 361 methanol and ethanol adsorb considerably more slowly than water. As discussed earlier, fastest adsorption rates arise when larger jumps from an equilibrium position are encountered therefore, Figure 22 shows results for comparable experiments involving a 0–90% step in relative vapor pressure for methanol, ethanol, and propanol. Further experiments involving similarly small acetone yields rates in a range somewhat comparable to ethanol. Penetration rates in the liquid state can be tracked by swelling experiments, or even by monitoring changes in tensile properties as a function of soak time. As with water, methanol and ethanol disrupt hydrogen bonding and so reduce the tensile properties of hair. Experiments performed with the Dia-stron Mini Tensile Tester (MTT) equipment described in Chapter 7, allow for testing to be performed while the hair soaks in a liquid. Consistent diminished tensile properties are obtained after only a few minutes when immersing hair fibers in water, but many hours are necessary before this state is attained for ethanol soaking. Figure 21. Adsorption of water, methanol and ethanol by hair when stepping the relative vapor pressure from 0-10% at 25oC