Adsorption Properties of Hair 362 (Unfortunately, attempts at performing similar experiments with acetone leads to dissolving of the plastic inner sheath of the brass ferrules). Given these results, it is still more evident that incursion into hair is not trivial, and we are forced to re-think the likelihood of bigger molecules having appreciable penetration. By means of example, perhaps the earliest known hair care treatment involved the application of oils, where a presumption exists that benefits extend beyond simple surface coating. This practice remains popular today, with a variety of exotic-sounding oils drifting in and out of popularity. Yet the size of the primary components of these ingredients leads to doubts about their penetration ability. Figure 23 shows the adsorption behavior of decane, which was used as a model for volatile oil interacting with hair. From the above arguments, any adsorption of this larger molecule is expected to be extremely slow. The adsorption curve in fact shows a relatively fast initial increase Figure 22. Adsorption of methanol, ethanol and propanol by hair when stepping the relative vapor pressure from 0–90% at 25oC