Adsorption Properties of Hair 360 Adsorption of Other Materials into Hair Stories about molecules penetrating into hair and providing salutary effects are commonplace in the hair care world. However, as just mentioned, even relatively small molecules appear to enter the hair rather slowly. Therefore, the ability for larger molecules, such as surfactants, oils and proteins, to penetrate and provide meaningful effects would appear more difficult again. Surprisingly, the scientific literature in this area is rather sparse. Some of our own fundamental studies33 have involved the DVS equipment described earlier (see Figure 9), but utilizing what the manufacturer terms “organics mode.” Here, water vapor is replaced as the adsorbing species and comparable experiments are performed using other volatile liquids. We began these studies using conventional anhydrous solvents that are commonly found in the laboratory. Figure 21 compares adsorption data for water, methanol and ethanol upon exposing dry hair to a 10% relative vapor pressure of each. Clearly even small, hydrogen-bonding molecules such as Figure 20. Adsorption isotherm for hair soaked in a 10% citric acid solution relative to an untreated control