Adsorption Properties of Hair 350 pressure of air is also highly temperature-dependant, and so, for example, a 10% jump in relative humidity at 35oC involves a greater change in the absolute atmospheric water content than the same jump at 25oC. Moreover, as highlighted above, faster adsorption rates are believed to arise when larger changes in absolute humidity are encountered. Table 1. Vapor pressures of water as a function of temperature18 Temperature Saturated Vapor Pressure Change in absolute vapor pressure due to 10% change in RH 5°C 6.54 mm Hg 0.654 mm Hg 15°C 12.79 mm Hg 1.279 mm Hg 25°C 23.76 mm Hg 2.376 mm Hg 35°C 42.18 mm Hg 4.218 mm Hg Table 2 shows half times for a 0–10% step in relative humidity as a function of temperature. Clearly, adsorption rates vary dramatically, with this occurrence likely possessing a contribution from both changing diffusion rates and driving forces dictated by atmospheric conditions. Table 2. Half-times for water adsorption rates by virgin hair when stepping the relative humidity from 0-10% as a function of temperature Temperature Half-time (t0.5) 5°C 90 mins 15°C 59 mins 25°C 41 mins 35°C 24 mins We have performed extensive studies regarding adsorption rates for water and hair across a wide range of humidity steps and a selection of temperatures.19 Results do indeed suggest that knowledge of the amount of water that adsorbs during a given